In current practice, an administrative user (2.2) is recorded by the
Attachment Daemon (2.1) in local file upsd.users
as being a Primary (2.8).
See Management of Administrative
Users (6.5.1) for an example. When a Management Daemon (2.6) starts up and opens a
Session (2.10) with the Attachment Daemon (2.1), it lays claim to being a Primary (2.8) by sending
command PRIMARY
to the Attachment Daemon (2.1), thus claiming that it has the
required authority to perform such critical actions as setting status
symbol FSD
.¶
Internet-Draft | UPS management protocol | December 2021 |
Price | Expires 1 July 2022 | [Page] |
- Workgroup:
- IETF
- Internet-Draft:
- draft-rprice-ups-management-protocol-05
- Published:
- Intended Status:
- Informational
- Expires:
Uninterruptible Power Supply (UPS) Management Protocol -- Commands and Responses
Abstract
This document describes the command/response protocol currently used in the management of Uninterruptible Power Supply (UPS) units and other power devices often deployed in small offices, and in IT installations subject to an erratic public power supply. The UPS units typically interface to an Attachment Daemon in the system they protect. This daemon is in turn polled by a Management Daemon which notifies users and system administrators of power supply incidents, and automates system shutdown decisions. The commands and responses described by this document are exchanged between the UPS Attachment Daemon and the Management Daemon. Current practice when this text was written risks weak security and this is addressed in the Security Considerations sections of this document.¶
Status of This Memo
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶
This Internet-Draft will expire on 1 July 2022.¶
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
1. Introduction
1.1. How to Read this Document
The editor recommends that you read the HTML
version of this document. It renders the protocol symbols such as
OL
correctly without quotation marks.¶
To lighten the text, the term "UPS" is used when "Managed Power Device" would be more complete. The reader should understand the simple "UPS" to include other managed power devices.¶
The statuses and events appearing in this document are named with short text-form names, some of which are abbreviations. A full list of the statuses can be found in section Status Symbols (5.1) while the events are listed in section Events (5.2).¶
This document refers to the "public power supply". Other texts frequently refer to "utility power", "input source power" or even "wall power".¶
1.2. Current Practice
This document describes UPS management techniques and current UPS management practice published by the NUT Project (2.7) which has been operational since 1998. Appendix The Shutdown Story (B) describes the current UPS management practice for performing a managed shutdown of unattended infrastructure after an unscheduled failure of the public power supply to minimise the risk of corruption to data processed by this infrastructure.¶
Since May 2002, the protocol described by this document has been operating on IANA port nut/3493 running over TCP.¶
1.3. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].¶
1.4. Additional Information
Additional information about the NUT Project (2.7) is available in the project documentation [Documentation]. Requests for further information about this protocol and related technical matters may be addressed to the mailing list [nut-upsuser] of the NUT Project (2.7).¶
2. Terminology
The following technical terms appear in this document. They are listed in alphabetical order.¶
2.1. Attachment Daemon
The Attachment Daemon retrieves status from the UPS and
sends commands to it often through a Driver (2.3) specific to the
hardware model and the connection medium, e.g., USB, serial. It
maintains an abstracted view of the hardware through the use
of hardware statuses (2.11). A Management Daemon (2.6) may
consult the abstracted view using the commands described in this
document. An Attachment Daemon is launched as system user "root" to
allow direct access to the hardware
(e.g. /proc
, /dev
). For better security, the daemon
then drops privilege to run as a detached software service for a
dedicated system user. It must support statuses (2.11) OB and OL. It must also support status LB if
the UPS provides such information.¶
2.2. Administrative User
In current practice, the commands and other functions
offered by the Attachment Daemon (2.1) to each Management Daemon (2.6) are made available to a set of
Management Daemon (2.6) users which authenticate to the Attachment Daemon (2.1) with basic credentials
(username and password). These users are not system users, they are
specific to an Attachment Daemon (2.1) and are listed in a text file which is read by
the Attachment Daemon (2.1) (currently upsd.users
) and which assigns to each of
them the password, instant commands (2.5) and actions which are allowed, together with
the Primary (2.8) or Secondary (2.9) status of the Management Daemon (2.6). For details,
see section (6.5.1). Typically a
high-level user will be able to send command FSD
(4.2.3) but a low-level
user might only be allowed to access the test panel. The security
provisions for administrative users are discussed in
section 6.5.¶
2.3. Driver
A Driver is that part of an Attachment Daemon which is specific to the UPS hardware, the connection medium and the connection protocol, e.g., USB, serial. In current practice the Attachment Daemon has a driver for each hardware interface type it supports. Although this document considers the driver to be part of the Attachment Daemon, current practice is to see it as a separate software unit running as a daemon "in front of" the Attachment Daemon. The protocol for data exchange between the Driver and the Attachment Daemon is outside the scope of this document.¶
2.4. Event
A UPS Event occurs in the Management Daemon (2.6) when a change in UPS status (2.11) is received from the Attachment Daemon (2.1). This event is internal to the Management Daemon (2.6). See Section 5.2, Paragraph 1.¶
2.5. Instant Command
A command which when sent to the Attachment Daemon (2.1) is passed to the
driver and sent to the hardware without any configured delay to
perform a function. For example INSTCMD su700
test.panel.start
. See INSTCMD
(4.2.6).¶
2.6. Management Daemon
The Management Daemon is primarily responsible for managing the hardware and orchestrating system-wide actions after a power event. Using commands sent to the Attachment Daemon (2.1) it follows the status of the UPS and determines when UPS events occur. It takes decisions based on the events, such as calling for a system shutdown (B). Although the term includes the word "daemon" nothing requires that it be implemented as a detached software service. The Management Daemon may also provide administrative functions such as a graphic interface to view the hardware activity.¶
2.7. NUT (Network UPS Tools) Software Project
The primary goal of the NUT software project [NUT] is to provide support for Power Devices, such as Uninterruptible Power Supplies. The Project has been in operation since 1998 with a major rework in 2003. It operates through a user mailing list [nut-upsuser], a developer mailing list [nut-upsdev] and a web site [NUT]. See the history of the project [History].¶
2.8. Primary
When a power device such as a UPS unit supplies power
to more than one system, the computer running the driver is known as
the primary. The others are secondaries. See
figure 4. Common current
practice for system administrators is to consider the Management Daemon (2.6) in the
primary to be the Primary Management Daemon which is in charge of the
shutdown of all the systems powered by the UPS. The Primary
Management Daemon sets status symbol FSD
to order the
secondaries to shut down.¶
Note: Historically, the primary was known as the "Master".¶
2.9. Secondary
When a hardware device such as a UPS unit supplies
power to more than one system, the system which communicates directly
with the UPS unit e.g. using a USB, RS232, or network connection, is
known as the Primary (2.8). The other are secondaries. There is no Attachment Daemon (2.1)
in a secondary. See figure 4.
Common current practice for system administrators is to consider the
Management Daemon (2.6) in a secondary to be a Secondary Management Daemon which
understands status symbol FSD
as an order to shut down.¶
Note: Historically, the secondary was known as the "Slave".¶
2.10. Session
The Management Daemon (2.6) may initiate a TCP session with a specified device such as a UPS known to the Attachment Daemon (2.1). The session structure provides for audit and security as well as access to mission critical UPS functions. For example good practice requires a password protection for an instant command (2.5) which turns off a UPS outlet. Other than the commands and responses used, the details of session management are outside the scope of this document.¶
2.11. UPS Status
The status of a hardware device such as a UPS unit is a
symbolic description of the state of the unit. It consists of a space
separated list of symbols from the set {ALARM
BOOST
BYPASS
CAL
CHRG
COMM
DISCHRG
FSD
LB
NOCOMM
OB
OFF
OL
OVER
RB
TEST
TRIM
}. The symbols TICK
and
TOCK
are experimental additions to the statuses and are not in
common current practice. See section Status Symbols (5.1) which specifies each of these symbols.
The statuses LB
, OB
and OL
MUST be supported for all units.
The other statuses are OPTIONAL and depend on the feature set of the
hardware.¶
2.12. UPS Variable
The metrics and identifiers provided by each UPS are
represented by variables giving the value representing that metric or
identifier, The UPS variable is an abstraction of the UPS hardware
configuration and activity maintained by the Attachment Daemon (2.1).
See the appendix (Appendix A, Paragraph 1) which provides examples
of variables. For example the variable battery.charge
contains the current charge of the UPS battery as a percentage value.
A full list is available in source code file
docs/nut-names.txt [gitvars] which serves as the Recording Document.¶
Note: Some variables are constants, e.g. battery type, manufacturer.¶
3. Protocol Overview
Figure 1 shows a reference configuration in which the command/response protocol applies. The UPS shown is representative of all power devices,¶
The reference configuration in figure 1 shows a single UPS unit which has a power supply link
(===
) and a data link (---
) attached to a system
running an Attachment Daemon (2.1). The UPS provides power supply protection to the
system running the Attachment Daemon.¶
In practice there may be more than one UPS unit, and a unit may provide power protection to more than one system. The figure also shows a single Management Daemon (2.6). In practice there may be more than one Management Daemon, and any one Management Daemon may manage more than one UPS Attachment Daemon.¶
The protocol applies to connections between the Attachment Daemon and the Management daemon which act as server and client respectively. The Management daemon sends commands over TCP to the Attachment Daemon and receives responses over TCP from that daemon.¶
The two daemons may run in the same system, or may be connected through a local or wide area network. In simple cases, as shown in figure 2, the Attachment Daemon (2.1) and the Management Daemon (2.6) are in the same system, the one protected by the UPS. The commands and responses are exchanged through an internal loopback interface.¶
The reference configuration does not require any specific design. For example figure 3 shows an arrangement in which the Attachment Daemon (2.1) is closely associated with, or even included in the UPS system setup. This is becoming more prevalent with the availability of low cost processors able to run the Attachment Daemon (2.1) thereby effectively creating a network attached UPS running a standard protocol.¶
As the power requirements for processors decrease, it is becoming
increasingly common to use a single UPS to protect multiple systems as
shown in figure 4. However
there is only one data line (---
) from the UPS to the Primary (2.8)
system. The others have only power connections (===
) to the
UPS, and are known as Secondaries (2.9). A Secondary (2.9) does not run an Attachment Daemon (2.1),
it connects over a network to the Attachment Daemon (2.1) in the
primary. Figure 4 shows the
Attachment Daemon (2.1) and the primary Management Daemon (2.6) in the same system. This is common
practice but it is not a technical requirement.¶
4. Protocol Specification
This specification includes only the commands and their responses.
An implementation of the Attachment Daemon (2.1) has an internal state machine, and some
complex implementations of the Management Daemon (2.6) include an internal state
machine; for example to assist the system shutdown of a complex
installation. The Management Daemon (2.6) is required to remember the
previous ups.status
value it received from the Attachment Daemon (2.1) and compare
it with the next. Other than that the management protocol used
between them is effectively stateless.¶
See for example table (5.2) which
maps the new ups.status
response and the
previous ups.status
response to an Event (5.2) which is taken as
the basis for Management Daemon (2.6) action.¶
4.1. Notation Used in this Specification
The character set used for commands and responses is UTF-8 but current practice is to limit the character set used to the single byte UTF-8 characters 0-127.¶
Multi-word elements are contained within U+0022 QUOTATION MARK characters for easier parsing. E.g., "UPS on fire". Embedded quotation marks are escaped with U+005C REVERSE SOLIDUS \ often known as backslashes. Embedded backslashes are also escaped by representing them as \\.¶
Commands and responses have no leading or trailing whitespace, and are terminated with a single new line character U+000A LINE FEED (LF).¶
White space within commands and responses is reduced to one U+0020 SPACE (SP).¶
4.2. Commands
The commands address the UPS to which they apply
by <upsname>
where¶
-
<upsname>
::=<ups>[@<hostname>[:<port>]]
¶ -
<ups>
is defined by the Attachment Daemon (2.1) configuration files.¶ - The default
<hostname>
islocalhost
¶ - The
<port>
is the number of the TCP port on which the Attachment Daemon (2.1) is listening. The default is 3493. This is supported by all current Management Daemons (2.6).¶
Examples: myups
, UPS-97B@bigserver.example.com
¶
Note: Experimental Management Daemons (2.6) use an extended form
of <upsname>
in configuration files and in program
parameters, where¶
-
<upsname>
::=[<group>:]<ups>[@<hostname>[:<port>]]
¶ -
<group>
is an experimental extension to provide for groups of UPSs. It is not in common current practice.¶ -
<ups>
is defined by the Attachment Daemon (2.1) configuration files.¶ - The default
<hostname>
islocalhost
¶
Examples: ups-1@example.com:3493
, HB:heartbeat1@example.com:3493
¶
4.2.1. ATTACH
In a configuration such
as Figure 4 in which a UPS protects more than
one system, the Primary (2.8) Management Daemon (2.6) needs to know how many Secondaries (2.9) are
currently "active", i.e., powered by the UPS, either from the
public power supply or from battery power. The Attachment Daemon (2.1) supports this by
keeping a count of all the "active" systems powered by a UPS.
The count is initialised, one secondary at a time by
the ATTACH
command, which should be understood as "count
this secondary as active". ATTACH
is one of three
commands for Secondary (2.9) counting: command DETACH
(4.2.2) decrements the count
and a Management Daemon (2.6) may read the count at any time using command NUMATTACH
(4.2.4.3).¶
The ATTACH
command is also sent to the Attachment Daemon (2.1) for the
primary so during normal, fully protected operation, the count is 1
for the primary + the number of secondaries. During a full system
shutdown, the count drops as each secondary Management Daemon (2.6) executes command
DETACH
(4.2.2) during its own shutdown. When the count drops to 1, only
the primary is "active" and it knows that all the secondaries
have shut down.¶
Command: ATTACH <upsname>
¶
If the command succeeds, the response is OK
, otherwise
see the error responses (4.3.2).¶
Note: Historically, this command was known as LOGIN
.
Since that LOGIN
was not the conventional user access to a
shell or program the name was changed to avoid confusion.¶
4.2.2. DETACH
This companion command to ATTACH
(4.2.1) reduces the
count of "active" Secondaries (2.9). It should be understood as "this
secondary is no longer active", and is usually used during system
shutdown to decrement a count of how many Secondaries (2.9) are still "active".¶
Command: DETACH
¶
If the command succeeds, the response is OK Goodbye
,
otherwise see the error
responses (4.3.2).¶
Note: Historically, this command was known as LOGOUT
.¶
4.2.3. FSD
A Management Daemon (2.6) which is Primary (2.8) and has the required
authority, uses this command to set status symbol FSD
meaning
"Forced Shutdown" in the Attachment Daemon (2.1). In current practice the Primary (2.8) Management Daemon (2.6)
uses the symbol to tell the Secondaries (2.9) to shut down.¶
Command: FSD <upsname>
¶
If the command succeeds, the response is OK FSD-SET
,
otherwise see the error
responses (4.3.2).¶
In current practice, commands such as FSD
are made
available only to a privileged administrative user (2.2) authorized to send such a mission
critical command. The security provisions for administrative users
are discussed in section 6.5.¶
4.2.4. GET
Retrieve a single response from the Attachment Daemon (2.1). The possible sub-commands are:¶
4.2.4.1. GET CMDDESC
Retrieve a text description of a command.¶
Command: GET CMDDESC <upsname> <cmdname>
¶
Response: CMDDESC <upsname> <cmdname> "<description>"¶
For example: GET CMDDESC su700 load.on
and
response CMDDESC su700 load.on "Turn on the load immediately"
¶
This is like DESC
(4.2.4.2), but it applies to an instant command (2.5).¶
4.2.4.2. GET DESC
Retrieve a text description of a variable.¶
Command: GET DESC <upsname> <varname>
¶
Response: DESC <upsname> <varname> "<description>"
¶
where <description> is a string that gives a brief explanation of the named variable. The Attachment Daemon (2.1) may return "Unavailable" if the file which provides this description is not installed.¶
For example command GET DESC su700 ups.status
and
response DESC su700 ups.status "UPS status"
¶
4.2.4.3. GET NUMATTACH
Retrieve the count kept by the Attachment Daemon (2.1) of all the "active" systems protected by this UPS.¶
Command: GET NUMATTACH <upsname>
¶
Response: NUMATTACH <upsname> <value>
¶
where <value> is a count of the Primary (2.8) and the number of Secondaries (2.9) currently powered by this UPS.¶
For example command GET ATTACH su700
and
response NUMATTACH su700 1
¶
This information is needed by the Management Daemon (2.6) to determine how many Secondaries (2.9) are still connected during the system shutdown process.¶
Note: Historically, this sub-command was known
as NUMLOGINS
. Since LOGIN
was not the conventional
user access to a shell or program the name was changed to avoid
confusion.¶
4.2.4.4. GET TYPE
Retrieve the type of a UPS variable (2.12).¶
Command: GET TYPE <upsname> <varname>
¶
Response: TYPE <upsname> <varname> <type>...
¶
where <type> can be one or more of the following tokens. Multiple types may be returned.¶
For example command GET TYPE su700 input.transfer.low
and
response TYPE su700 input.transfer.low ENUM
¶
Type | Meaning |
---|---|
RW | This is a read/write variable. It may be read with
command GET VAR (4.2.4.6) and set to a different value with command
SET (4.2.11)
|
ENUM | An enumerated type, which supports specific predetermined values |
STRING:n | This is a string of maximum
length n
|
RANGE |
This is a number, either integer or
float, comprised in the range which may be seen with the
command |
NUMBER | This is a single numeric value, either integer or float |
Notes:¶
- ENUM, STRING:n and RANGE are usually associated with RW, but not always. The default <type>, when omitted, is numeric, so either integer or float. Each Driver (2.3) is then responsible for handling values as either integer or float.¶
- Current practice is to represent floating point values using
locale
C.utf8
which is a decimal (base 10) US English-based representation. Hexadecimal, exponents, and comma for thousands separator are not allowed. For example: "1200.20" is valid, while "1,200.20" and "1200,20" are not valid.¶
4.2.4.5. GET UPSDESC
Retrieve a text description of a UPS.¶
Command: GET UPSDESC <upsname>
¶
Response: UPSDESC <upsname> "<description>"
¶
where <description> is defined by the Attachment Daemon (2.1) configuration. If it is not set, current practice is for the Attachment Daemon (2.1) to return "Unavailable".¶
For example command GET UPSDESC su700
and response
UPSDESC su700 "Development box"
¶
This can be used to provide human-readable descriptions instead of
a cryptic ups@hostname
string.¶
4.2.4.6. GET VAR
Retrieve the value of a UPS variable (2.12).¶
Command: GET VAR <upsname>
<varname>
¶
Response: VAR <upsname> <varname> "<value>"
¶
For example command GET VAR su700 ups.status
and response
VAR su700 ups.status "OB LB"
¶
4.2.5. HELP
Return a list of the commands supported by the Attachment Daemon (2.1). This command is intended for human as well as program use.¶
Command HELP
¶
For example, the following command line sequence executed on an Attachment Daemon (2.1):¶
netcat localhost 3493 HELP Commands: HELP VER GET LIST SET INSTCMD ATTACH DETACH USERNAME PASSWORD STARTTLS¶
Note:
Historically, this command also
returned LOGIN
and LOGOUT
. Since LOGIN
was
not the conventional user access to a shell or program, the command
names were changed to ATTACH
and DETACH
avoid confusion.¶
4.2.6. INSTCMD
Send an instant command (2.5) to the UPS.¶
Command: INSTCMD <upsname> <cmdname>
¶
where <upsname>
is the name of the UPS
and <cmdname>
is the instant command (2.5) to be issued to that UPS.¶
If the command succeeds, the response is OK
, otherwise
see the error responses (4.3.2).¶
For example the command: INSTCMD su700 test.panel.start
and the response OK
¶
4.2.7. LIST
The LIST
commands all produce a response
with a common format. The response will begin with BEGIN LIST
and then repeat the initial query. A list then follows, with as many
lines as are necessary. The response ends with END LIST
followed by the initial query.¶
The formatting may seem a bit redundant, but it makes a different
form of client possible. A client can send a LIST
(4.2.7) query and then
wait for the response. When it arrives, the Management Daemon (2.6) doesn't need a
complicated state machine to remember which list is which.¶
Note: The current NUT Project (2.7) implementation of the
Attachment Daemon (2.1), upsd
, sends back the response to a LIST
(4.2.7) command as
a sequence of messages. The Management Daemon (2.6) should continue reading these
messages until it receives the line beginning END
LIST
.¶
The possible subcommands are:¶
4.2.7.1. LIST CLIENT
The command calls for the Attachment Daemon (2.1) to report all the current Management Daemon (2.6) clients of a given UPS.¶
Command: LIST CLIENT <upsname>
¶
The response is¶
BEGIN LIST CLIENT <upsname> CLIENT <upsname> <client_IP_address> ... END LIST CLIENT <upsname>¶
For example, the command LIST CLIENT ups1
and the response:¶
BEGIN LIST CLIENT ups1 CLIENT ups1 ::1 CLIENT ups1 198.51.100.2 END LIST CLIENT ups1¶
4.2.7.2. LIST CMD
The command calls for the Attachment Daemon (2.1) to report a list of the instant commands (2.5) which the Management Daemon (2.6) may send to the Attachment Daemon (2.1). This instant command (2.5) list is the abstracted view of the UPS hardware capabilities. An economical UPS will support few or no instant commands (2.5) but a professional model should support more.¶
Command: LIST CMD <upsname>
¶
The response is:¶
BEGIN LIST CMD <upsname> CMD <upsname> <cmdname> ... END LIST CMD <cmdname>¶
where <upsname>
is the name of the UPS,
and <cmdname>
is the name of the command which may be
issued to the UPS.¶
For example the command: LIST CMD su700
and the response:¶
BEGIN LIST CMD su700 CMD su700 load.on CMD su700 test.panel.start ... END LIST CMD su700¶
4.2.7.3. LIST ENUM
The command calls for the Attachment Daemon (2.1) to report the set of possible values of a UPS variable (2.12) which has predetermined values.¶
Command: LIST ENUM <upsname> <varname>
¶
The response is:¶
BEGIN LIST ENUM <upsname> <varname> ENUM <upsname> <varname> "<value>" ... END LIST ENUM <upsname> <varname>¶
where <upsname>
is the name of the UPS,
<varname>
is the UPS variable (2.12) and <value>
is
one of the possible values of that UPS variable (2.12). Note that in current
practice the output is an unordered list. Note also that the U+0022
QUOTATION MARK characters are part of the response.¶
For example the command: LIST ENUM su700 input.transfer.low
and the
response:¶
BEGIN LIST ENUM su700 input.transfer.low ENUM su700 input.transfer.low "103" ENUM su700 input.transfer.low "100" ... END LIST ENUM su700 input.transfer.low¶
4.2.7.4. LIST RANGE
The command calls for the Attachment Daemon (2.1) to report the interval in which valid values of UPS variable (2.12) lie.¶
Command: LIST RANGE <upsname> <varname>
¶
The response is:¶
BEGIN LIST RANGE <upsname> <varname> RANGE <upsname> <varname> "<min>" "<max>" ... END LIST RANGE <upsname> <varname>¶
where <upsname>
is the name of the UPS,
<varname>
is the UPS variable (2.12) and
{<min>
,<max>
} is the interval of valid
values of that UPS variable (2.12). Note that the U+0022 QUOTATION MARK characters
are part of the response.¶
For example, the command LIST RANGE su700
input.transfer.low
and the response:¶
BEGIN LIST RANGE su700 input.transfer.low RANGE su700 input.transfer.low "90" "105" END LIST RANGE su700 input.transfer.low¶
4.2.7.5. LIST RW
The command calls for the Attachment Daemon (2.1) to report a list of the UPS variables (2.12) associated with a given UPS which may be read and written by the Management Daemon (2.6). These variables are the abstracted view of the UPS hardware capabilities. An economical UPS may support few variables but a professional model should support at least the variables which are needed for an automatic shutdown and restart (B).¶
Command: LIST RW <upsname>
¶
The response is:¶
BEGIN LIST RW <upsname> RW <upsname> <varname> "<value>" ... END LIST RW <upsname>¶
where <upsname>
is the name of the UPS,
<varname>
is the UPS variable (2.12) and
<value>
is the value of that UPS variable (2.12). Note that
the U+0022 QUOTATION MARK characters are part of the response.¶
For example the command: LIST RW su700
and the response:¶
BEGIN LIST RW su700 RW su700 output.voltage.nominal "115" RW su700 ups.delay.shutdown "020" ... END LIST RW su700¶
4.2.7.6. LIST UPS
The command calls for the Attachment Daemon (2.1) to report a list of the UPS units to which it is attached.¶
Command: LIST UPS
¶
The response is:¶
BEGIN LIST UPS UPS <upsname> "<description>" ... END LIST UPS¶
where <upsname> is the name of a UPS, and <description> is the description maintained by the Attachment Daemon (2.1) if available. It is set to "Unavailable" otherwise. Note that the U+0022 QUOTATION MARK characters are part of the response.¶
This command can also be used to determine what values of <upsname> are valid before calling other functions on the server. This is also a good way to handle situations where a single Attachment Daemon (2.1) supports multiple UPS's. It is also useful for clients which perform a UPS discovery process.¶
For example, the response:¶
BEGIN LIST UPS UPS su700 "Development box" END LIST UPS¶
4.2.7.7. LIST VAR
The command calls for the Attachment Daemon (2.1) to report a list of all the UPS variables (2.12) which it maintains for a given UPS, and the values of those variables.¶
Command: LIST VAR <upsname>
¶
The response is:¶
BEGIN LIST VAR <upsname> VAR <upsname> <varname> "<value>" ... END LIST VAR <upsname>¶
where <upsname>
is the name of the UPS,
<varname>
is the UPS variable (2.12) and
<value>
is the value of that variable. Note that
the U+0022 QUOTATION MARK characters are part of the response.¶
The response to this command lists the UPS variables (2.12) available for this
UPS and their current values. For example the command LIST VAR
su700
and the response:¶
BEGIN LIST VAR su700 VAR su700 ups.mfr "Example Mfg" VAR su700 ups.mfr.date "10/17/96" ... END LIST VAR su700¶
4.2.8. PASSWORD
This command is a companion to USERNAME
(4.2.13), and is used by a Management Daemon (2.6) to
specify the password required to enter a Session (2.10) with the Attachment Daemon (2.1).¶
Command: PASSWORD <password>
¶
If the command succeeds, the response is OK
, otherwise
see the error responses (4.3.2).¶
For examples of the use of commands USERNAME
(4.2.13) and PASSWORD
by
administrative users (2.2) see Section 6.5.2, Paragraph 1.¶
4.2.9. PRIMARY
Command: PRIMARY <upsname>
¶
where <upsname>
is the name of the UPS.¶
If the Attachment Daemon (2.1) has the authority, the response is OK
, otherwise
see the error responses (4.3.2).¶
Note: Historically, this command was known as MASTER
.¶
4.2.10. PROTVER
Return the implementation version of the command/response protocol used by the Attachment Daemon (2.1). This command is intended for human as well as program use.¶
Command PROTVER
¶
For example, the following command line sequence in the Attachment Daemon (2.1):¶
netcat localhost 3493 PROTVER 1.2¶
Notes:¶
- There are no U+0022 QUOTATION MARK characters in the response.¶
- Historically, this command was known as
NETVER
and current practice is to useNETVER
instead of PROTVER.¶ - The implementation version of the protocol returned by PROTVER is
different to the implementation version of the Attachment Daemon (2.1) returned by
VER
(4.2.14).¶
4.2.11. SET
The command calls for the Attachment Daemon (2.1) to set a UPS variable (2.12) to a given value. Whether this has an effect on the UPS hardware is specific to the Driver (2.3) and the UPS model. Some variables are read-only due to the design of the UPS or its driver.¶
Command: SET VAR <upsname> <varname>
"<value>"
¶
where <upsname>
is the name of the UPS,
<varname>
is the UPS variable (2.12) and
<value>
is the value to be assigned to that variable.
Note that the U+0022 QUOTATION MARK characters are part of the
command.¶
If the command succeeds, the response is OK
, otherwise
see the error responses (4.3.2).¶
For example the command: SET VAR su700 ups.id "My UPS"
and
the response OK
¶
4.2.12. STARTTLS
The client tells the Attachment Daemon (2.1) to switch to TLS
encrypted communication. When the client receives OK
it also
switches to TLS encryption. The parameters and versions of
cryptographic libraries are those of the Attachment Daemon's
underlying OS and are outside the scope of this document.¶
Command: STARTTLS
¶
If the command succeeds, the response is OK STARTTLS
, otherwise
see the error responses (4.3.2).¶
4.2.13. USERNAME
The Attachment Daemon (2.1) limits access to clients whose
credentials match those in the file upsd.users
. There is no
anonymous access. A Management Daemon (2.6) program or script uses
command USERNAME
and its companion command PASSWORD
(4.2.8) to
open a Session (2.10) for an administrative user (2.2) with the Attachment Daemon (2.1), Note that this command is
for program or script use and is not the familiar login command typed
on a command line to gain access to a shell.¶
Command: USERNAME <username>
¶
If the command succeeds, the response is OK
, otherwise
see the error responses (4.3.2).¶
For examples of the use of commands USERNAME
and
PASSWORD
(4.2.8) by administrative users (2.2) see Section 6.5.2, Paragraph 1.¶
4.2.14. VER
Return the implementation version of the Attachment Daemon (2.1). This command is intended for human as well as program use.¶
Command VER
¶
For example, the following command line sequence:¶
netcat localhost 3493 VER Network UPS Tools upsd 2.7.4 - http://www.networkupstools.org/¶
Notes:¶
4.3. Summary of Responses
4.3.1. Response when Command Succeeds
If the command succeeds, the response has the following command-dependent form:¶
Command | Response | Note |
---|---|---|
ATTACH (4.2.1) |
OK |
Was LOGIN |
DETACH (4.2.2) |
OK Goodbye |
Was LOGOUT |
FSD (4.2.3) |
OK FSD-SET |
|
GET (4.2.4) |
Sub command specific | |
HELP (4.2.5) |
List of commands | |
INSTCMD (4.2.6) |
OK |
|
LIST (4.2.7) |
Sub command specific | |
PASSWORD (4.2.8) |
OK |
|
PRIMARY (4.2.9) |
OK |
|
PROTVER (4.2.10) |
Protocol version | Was NETVER |
SET (4.2.11) |
OK |
|
STARTTLS (4.2.12) |
OK STARTTLS |
|
USERNAME (4.2.13) |
OK |
|
VER (4.2.14) |
Program version |
4.3.2. Error Responses
Error responses have the following format:¶
ERR <error-name> [<extra>]¶
where <error-name>
is a single word token taken from
the 27 characters A-Z and U+002D HYPHEN-MINUS. Implementations may if
needed add an additional optional <extra>
. Current
practice does not make use of this possibility.¶
The <error-name>
may have one of the following
values:¶
The error name token
<error-name>
|
Meaning |
---|---|
ACCESS-DENIED
|
The client's host and/or authentication details (username, password) are not sufficient to execute the requested command. |
ALREADY-ATTACHED
|
The client has already sent a
successful Note: Historically, this error response was |
ALREADY-SET-PASSWORD
|
The client has already supplied a PASSWORD and is attempting to repeat the command in the same Session (2.10). |
ALREADY-SET-USERNAME
|
The client has already supplied a USERNAME, and is attempting to repeat the command within the same Session (2.10). |
CMD-NOT-SUPPORTED
|
The specified UPS doesn't support the instant command (2.5) command. |
DATA-STALE
|
The Attachment Daemon (2.1) is connected to the Driver (2.3) for the UPS, but that driver isn't providing regular updates or has specifically marked the data as stale. Current practice is for the Attachment Daemon (2.1) to refuse to provide the Management Daemon (2.6) with variables on stale units to avoid false readings.¶ This generally means that the Driver (2.3) is running, but it has lost communication with the hardware. Check the physical connection to the equipment.¶ |
DRIVER-NOT-CONNECTED
|
The Attachment Daemon (2.1) can't perform the requested command, since the Driver (2.3) for that UPS is not connected. This usually means that the driver is not running, or if it is, is misconfigured. |
FEATURE-NOT-CONFIGURED
|
This instance of the Attachment Daemon (2.1)
hasn't been configured properly to allow the requested feature to
operate. In current practice this error response is possible only for
command STARTTLS (4.2.12).
|
FEATURE-NOT-SUPPORTED
|
This instance of Attachment Daemon (2.1) does
not support the requested feature. In current practice this error
response is possible only for command STARTTLS (4.2.12).
|
INSTCMD-FAILED
|
The Attachment Daemon (2.1) failed to deliver the instant command (2.5) request to the Driver (2.3). No further information is available to the client. This typically indicates a dead or broken driver. |
INVALID-ARGUMENT
|
The client sent an argument to a
command which is not recognized or is otherwise not valid in this
context. This is typically caused by sending a valid command such as
GET (4.2.4) with a subcommand which is not valid.
|
INVALID-PASSWORD
|
The client sent a non valid password. |
INVALID-USERNAME
|
The client sent an non valid username. |
INVALID-VALUE
|
The value specified in the request
is not valid. This usually applies to a SET (4.2.11) of an ENUM (4.2.7.3) type
which is using a value not in the list of allowed values.
|
PASSWORD-REQUIRED
|
The command requires a password for authentication, but the client hasn't provided one. |
READONLY
|
The requested variable in a SET (4.2.11)
command is not writable.
|
SET-FAILED
|
The Attachment Daemon (2.1) failed to deliver the set
request to the Driver (2.3). This is similar to INSTCMD-FAILED .
|
TLS-ALREADY-ENABLED
|
TLS mode is already enabled on this connection, so the Attachment Daemon (2.1) can't start it again.¶ Note: Historically, this message was |
TLS-NOT-ENABLED
|
TLS mode has not yet been enabled on this connection, so the Attachment Daemon (2.1) can't send commands.¶ Note: This message is experimental and not in current common use.¶ |
TOO-LONG
|
The requested value in a SET (4.2.11) command
is too long.
|
UNKNOWN-COMMAND
|
The Attachment Daemon (2.1) doesn't recognize the command. |
UNKNOWN-UPS
|
The UPS specified in the request is not known to the Attachment Daemon (2.1). This usually means that it didn't match anything in the Attachment Daemon (2.1) configuration. |
USERNAME-REQUIRED
|
The command requires a username for authentication, but the client hasn't provided one. |
VAR-NOT-SUPPORTED
|
The specified UPS doesn't support the UPS variable (2.12) in the command. |
5. Statuses and Events
5.1. Status Symbols
These symbols resume the abstracted view of the
UPS hardware maintained by the Attachment Daemon (2.1). The
variable ups.status
contains one or more space-separated
status symbols which together describe the UPS state at that instant.
In current practice the Management Daemon (2.6) will poll variable ups.status
every 5 seconds with a command such as GET VAR su700
ups.status
and response VAR su700 ups.status "OB LB"
to
discover changes in the UPS status. These changes will indicate UPS
events.¶
Status Symbol | Meaning |
---|---|
ALARM
|
The UPS reports that it requires intervention. |
BOOST
|
The UPS has determined that the voltage level of the input power supply is too low, and is boosting it to the required level. The UPS continues to supply the protected system from the input power supply. |
BYPASS
|
The UPS is feeding current directly from the input power supply to the protected system. The backup facilities are disconnected. This state allows maintenance personnel to change the batteries without interrupting the protected system. |
CAL
|
The UPS is calibrating itself, for example to determine at what
charge the LB status is raised or lowered.
|
CHRG
|
The UPS battery is charging. This usually implies that the UPS
also has status |
COMM
|
The Attachment Daemon (2.1) has effective contact with the UPS. |
DISCHRG
|
The UPS battery is discharging. This usually implies that the UPS
also has status |
FSD
|
This "Forced Shutdown" status signals that the final shutdown sequence has begun. |
LB
|
Low Battery. The battery level of the UPS is below a chosen limit. The UPS may be in status OL or OB. |
NOCOMM
|
The Attachment Daemon (2.1) has no effective contact with the UPS. |
OB
|
On Battery. The UPS is taking energy from it's battery.
The battery is discharging. A UPS must have status OB or OL ,
otherwise it is deemed dead.
|
OFF
|
The UPS is in state "Off". It does not react to failure in the input power supply. The exact meaning depends on the model. |
OL
|
Online. The UPS is online, receiving energy from the input power
supply. The battery is charging. A UPS must have status OB or
OL , otherwise it is deemed dead.
|
OVER
|
Overloaded. The UPS reports that the load on it is beyond it's normal operating maximum. |
RB
|
Replace battery. The UPS reports that it's battery/batteries should be replaced. |
TEST
|
Under test. The UPS is currently undergoing a test, which may have been called for manually or internally. |
TICK
|
Heartbeat. A software UPS in the Attachment Daemon (2.1) provides a regular signal
monitored by the Management Daemon (2.6) as a way of verifying effective end-to-end
management. TICK and TOCK are companions, they are considered
experimental.
|
TOCK
|
Heartbeat. See TICK
|
TRIM
|
The UPS has determined that the voltage level of the input power supply is too high, and is reducing it to the required level. The UPS continues to supply the protected system from the input power supply. |
5.2. Events
A Management Daemon (2.6) detexts the occurrence of a UPS Event from a
change in the UPS status (2.11) received from the Attachment Daemon (2.1). The following table
summarizes the process. A status of "none" means that the status
symbol is not present in the variable ups.status
.¶
The Management Daemon (2.6) should retrieve the variable ups.status
from the
Attachment Daemon (2.1) at regular intervals. If the interval is too short, compute and
network resources will be wasted, but if the interval is too large,
the Management Daemon (2.6) risks missing short-lived changes in the UPS status.¶
A default value of 5 seconds is recommended, but an implementation may make this value configurable. By default the "old" status is therefore the previous value retrieved 5 seconds ago.¶
Current practice is for the Management Daemon (2.6) to assign names to certain events. These is shown in the table in parentheses.¶
Old status | New status | Event | Old status | New status | Event | |
---|---|---|---|---|---|---|
none |
ALARM |
Alarm on |
ALARM |
none | Alarm off | |
none |
BOOST |
Boosting voltage |
BOOST |
none | Not boosting | |
none |
BYPASS |
Bypass on |
BYPASS |
none | Bypass off | |
none |
CAL |
Calibrating |
CAL |
none | Not calibrating | |
none |
CHRG |
Charging |
CHRG |
none | Not charging | |
none |
COMM |
UPS communicating ( COMMOK ) |
COMM |
none | See note 4 | |
none |
DISCHRG |
Discharging |
DISCHRG |
none | Not discharging | |
none |
FSD |
System shutdown ( FSD ) (SHUTDOWN ) |
FSD |
none | Shutdown abandoned. See note 1 | |
none |
LB |
Low battery. See note 2 ( LOWBATT ) |
LB |
none | Battery not low | |
none |
NOCOMM |
UPS dead? See note 4 ( COMMBAD ) (NOCOMM ) |
NOCOMM |
none | See note 4 | |
none |
OFF |
UPS turned off |
OFF |
none | UPS not turned off | |
OB |
OL |
Receiving wall power ( ONLINE ) |
OL |
OB |
Wall power lost ( ONBATT )
|
|
none |
OVER |
UPS overloaded |
OVER |
none | Overload gone | |
none |
RB |
Replace battery ( REPLBATT ) |
RB |
none | Replacement canceled | |
none |
TEST |
Test starts |
TEST |
none | Test finished | |
none |
TICK |
Heartbeat event. See note 3 |
TICK |
none | No heartbeat. See note 3 | |
none |
TOCK |
Heartbeat event. See note 3 |
TOCK |
none | No heartbeat. See note 3 | |
none |
TRIM |
Trimming voltage |
TRIM |
none | Not trimming |
Notes¶
-
Current practice does not include this event.¶
-
If the status
OB
is present, current practice takes Management Daemon (2.6) reception ofLB
as an order to perform an emergency system shutdown.¶ -
The use of a software defined UPS to provide a heartbeat is experimental and is not part of common current practice.¶
-
Current practice is: if the UPS has not responded for 15 seconds, the Management Daemon (2.6) assumes that the UPS is "dead" (
NOCOMM
), and if the last knownOL
/OB
status wasOB
a system shutdown (FSD
) is called for.¶
6. Security Considerations
The security issues raised by UPS management are those of the power industry in general: they are addressed in detail in Technical Specification IEC 62351-1 [IEC62351-1]. In addition to equipment security, cyber security is now an essential consideration.¶
Quoting from IEC 62351-1 clause 5.2.3.5 [IEC62351-1]:¶
With the computer systems for power operations presumably kept isolated from the Internet, many utility personnel do not see any reason for adding security measures to these systems. However, as clearly seen from these Subclauses, this may not be true anymore as networking becomes more prevalent and additional information access requirements grow.¶
Clause 5.3.5 [IEC62351-1] lists the typical security attacks:¶
Eavesdropping, Masquerade, Man-in-the-Middle, Replay, Resource Exhaustion¶
Additionally the UPS management protocol provides means for a Management Daemon (2.6) to shut down a working system and it's power supply as described in The Shutdown Story (B). A malicious client acting as a Management Daemon (2.6) could turn off the UPS power outlets causing the system to fail.¶
Most of these issues are well known IT issues concerning system protection and disaster recovery, and are beyond the scope of this document, however the protocol itself has security considerations:¶
- It should not be possible for non-authorized agents to open
sessions and send mission-critical commands such as
FSD
(4.2.3) to the Attachment Daemon (2.1).¶ - It should not be possible to intercept the traffic between the Attachment Daemon (2.1) and the Management Daemon (2.6).¶
Let's look more closely at these requirements.¶
6.1. Agent Verification
The protocol provides commands USERNAME
(4.2.13) and
PASSWORD
(4.2.8) which allow an administrative user (2.2) in a Management Daemon (2.6) to authenticate itself to
the Attachment Daemon (2.1). The administrative user (2.2) name and password need protection from sniffing:
this is done by encrypting the traffic.¶
6.2. Current Encryption Practice
The protocol provides command STARTTLS
(4.2.12) which calls
on the Attachment Daemon (2.1) to support TLS encryption of the communication. If this
command is accepted, the Management Daemon (2.6) also encrypts.¶
In current NUT Project (2.7) practice, the use of TLS is optional and to
enforce it the system administator must set
declarations FORCESSL
to 1 and CERTVERIFY
to 1 in
the Management Daemon (2.6) configuration file.¶
At present the command STARTTLS
(4.2.12) is too frequently refused, and
traffic proceeds unencrypted, with plain text transmission of
passwords and status values.¶
A further weakness is that the FORCESSL
and CERTVERIFY
declarations are in the Management Daemon (2.6) configuration
file and not in the Attachment Daemon (2.1). Secure practice requires enforcement by
the Attachment Daemon (2.1) rather than a possibly rogue Management Daemon (2.6) out on the Internet.¶
6.2.1. Secure Tunnels
Some system administrators currently use techniques such as stunnel [stunnel] to encrypt the commands and responses, but the NUT Project (2.7) has no procedure to enforce this on sites.¶
6.3. Current General Security Practice
Experience over the last 20 years shows that new UPS management software releases are not frequent, and when installed, stay unmodified for some years. This is probably because UPS management is a mature hardware dependent activity. A limited number of system administrators have access to the UPS hardware and software and tend to assume a certain "security by obscurity" since many installations have a configuration as shown in figure 5 which uses port nut/3493 between the two daemons running in the same system. The traffic is often not encrypted, and when encrypted uses deprecated early versions of SSL/TLS.¶
This situation is now changing as low cost processors become available, costing significantly less than a UPS unit. This evolution makes it interesting to shift to a configuration as shown in figure 6, but it also exacerbates the security weakness of figure 5 since the traffic between the daemons is now over an exposed network.¶
6.4. Security Needs
UPS management needs to move to a more secure practice in which all traffic is encrypted, but this cannot be imposed by a wave of the hand: it cannot be implemented quickly and without impact to many deployed systems. The ideal would be an easy-to-follow migration plan which provides the required encryption but tolerates the slow moving updates of the UPS software.¶
Here are four examples of possible temporary solutions.¶
6.4.1. Shims
A possible technique introduces shims between the Attachment Daemon (2.1) and the network, and between the network and the Management Daemon (2.6) as shown in figure 7. These shims provide TLS support [RFC8446], allowing the Attachment Daemon (2.1) and Management Daemon (2.6) to continue temporarily without native TLS. The technique has been successfully tested, but the principal difficulty is that the shims make use of a second port which is not currently available.¶
6.4.1.1. Attachment Daemon Shim
The shim in front of the Attachment Daemon (2.1) listens to incoming traffic on a
port to be specified. When it receives the command STARTTLS
(4.2.12) it¶
- Returns
OK
to the client and sets up TLS encapsulation.¶ - Does not send
STARTTLS
(4.2.12) to the Attachment Daemon (2.1) port nut/3493.¶
All other commands and responses are passed through.¶
6.4.1.2. Management Daemon Shim
The shim in front of the Management Daemon (2.6) listens for incoming traffic on port
nut/3493. When it receives the command STARTTLS
(4.2.12) it¶
- Returns
FEATURE-NOT-CONFIGURED
to the client.¶ - Sends
STARTTLS
(4.2.12) to the Attachment Daemon (2.1) on a port to be specified.¶
All other commands and responses are passed through.¶
6.4.2. SSH Tunnels
Another possible technique is the use of SSH tunnels, using a software such as stunnel [stunnel] which adds OpenSSL-based TLS support without modifying the Attachment Daemon (2.1) or Management Daemon (2.6).¶
6.4.3. VPN
A further option to secure communications is very similar to SSH tunnelling and consists of routing the NUT traffic through a VPN.¶
6.4.4. VLAN
A fourth option is to isolate the UPS management traffic at the network switching level using a VLAN technique.¶
In figure (8) there are two VLANS: The main traffic between the protected server and its clients uses the production VLAN. The UPS management traffic between the attachment and management daemons uses the UPS management VLAN.¶
6.4.5. Long Term: Enforced Secure Communication
In the long term, enforcing secure communication requires
tightening up the Attachment Daemon (2.1) to require the use of command STARTTLS
(4.2.12) for
commands sent over the global Internet. In such a situation an Attachment Daemon (2.1)
listening for traffic other than from the localhost
:¶
-
MUST encrypt all communication with a Management Daemon (2.6),¶
Notes:¶
- The "SHOULD" rather than "MUST" in 1 above allows system administrators to enforce secure
communication using other techniques which do not involve the
STARTTLS
(4.2.12) command.¶ - If an Attachment Daemon (2.1) requires that all commands be encrypted as required by the "MUST" in 2 above, then automatically each Management Daemon (2.6) must encrypt as well, since it has to do so in order to gain access.¶
- The "SHALL" in 3 above applies to
traffic from the global Internet. An Attachment Daemon (2.1) MAY accept unencrypted
commands from
localhost
if the local installation's security practices allow it, for example in a dedicated appliance.¶ - Note that the separate management of strongly secure traffic from
the global Internet and weakly secure traffic from
localhost
can be achieved by using two ports:nut/3493
for the current weakly secure traffic fromlocalhost
, and some other port, perhapsups/TBD1
, for enforced secure communication, much in the manner ofhttp
andhttps
.¶
6.5. Administrative Security
Administrative commands such as FSD
(4.2.3), INSTCMD
(4.2.6)
and SET
(4.2.11) are powerful and can have a deep effect on system
integrity, For example, the command FSD
(4.2.3) is involved in mission
critical system shutdown decisions. Access to them needs to be
managed and restricted. This clause presents the current practice.¶
6.5.1. Management of Administrative Users
The Attachment Daemon (2.1) maintains a file
(currently upsd.users
) defining each administrative user (2.2). Note that these
users are independent of those recorded in file /etc/passwd
.
Each administrative user gets its own section in
file upsd.users
. The declarations in that section set the
parameters which define that user's privileges. The section begins
with the name of the user enclosed in square brackets, U+005B LEFT
SQUARE BRACKET [ and U+005D RIGHT SQUARE BRACKET ], and continues
until the next user name in brackets or EOF.¶
For example the following file declares two administrative users (2.2) admin
and pfy
:¶
[admin] password = sekret upsmon master actions = SET instcmds = ALL [pfy] password = sekret instcmds = test.panel.start instcmds = test.panel.stop¶
Within each section the administrative user (2.2) declarations are:¶
Declaration | Meaning |
---|---|
actions
|
Allow the user to do certain things in the Attachment Daemon (2.1). To specify multiple actions, use multiple instances of the declaration. Valid actions are:¶ |
instcmds
|
Let a user initiate specific instant commands. See section
INSTCMD (4.2.6). Use value ALL to grant all commands
automatically. To specify multiple commands, use multiple
instances of the instcmds field. For the full list of what a
given UPS supports, use client upscmd -l supplied by
the NUT Project (2.7).
|
password
|
Set the password for this user. Your password should be more secure than the examples shown. |
upsmon
|
Add the necessary actions for a Management Daemon (2.6) to process a system
shutdown. In current practice the value is still master
or slave . Note that there is no U+003D EQUALS SIGN =.
|
6.5.2. An Administrative User of a Client Management Daemon
The following examples show the current
security practices for administrative users (2.2) of a client Management Daemon (2.6) They also illustrate
the command pair USERNAME
(4.2.13) and PASSWORD
(4.2.8).¶
6.5.2.1. An Administrative User Logs into a Short Session
In this simple example of current practice, the system
administrator sets the battery level at which an Attachment Daemon (2.1) will raise the
status LB
, represented by variable battery.charge.low
, to
35% of full charge. A system administrator types the following command
to call the client upsrw
supplied by the
NUT Project (2.7).¶
upsrw -s battery.charge.low=35 -u admin -p sekret UPS-1@example.com¶
The USERNAME
(4.2.13) and PASSWORD
(4.2.8) commands are issued within the
client upsrw
and the Session (2.10) is of short duration.¶
6.5.2.2. An Administrative User Logs into a Long Session
In this second example of current practice, the long-running
Attachment Daemon (2.1) upsmon
which is responsible for initiating system
shutdowns and which is provided by the NUT Project (2.7) issues commands
USERNAME
(4.2.13) and PASSWORD
(4.2.8) when it starts up. The data needed for the
USERNAME
(4.2.13) and PASSWORD
(4.2.8) is provided by a configuration
file upsmon.conf
which contains the
line¶
MONITOR UPS-1@example.com 1 admin secret master¶
This says that the UPS to be monitored
is UPS-1@example.com
, it provides 1 single power supply, the
administrative user (2.2) is admin
with password secret
. The Management Daemon (2.6) acts
as a Primary (2.8), although current practice uses the term master
.¶
The USERNAME
(4.2.13) and PASSWORD
(4.2.8) commands are contained within the
client upsmon
and the Session (2.10) is of long duration.¶
7. Codepoint Management
This document raises five matters of codepoint management:¶
- The namespaces occupied by the protocol commands (4.2) described in this document.¶
- The namespaces occupied by the protocol responses (4.3.2) described in this document.¶
- The namespace occupied by UPS status (2.11) names,¶
- The namespace occupied by UPS variable (2.12) names,¶
- The port name and port number used to manage UPS units.¶
7.1. Namespaces used by Command, Responses, Statuses and Variables
Current NUT Project (2.7) experience after more than 20 years is that the UPS management area advances slowly, and that there are few requests to modify or extend the Commands, Responses, Statuses and Variables. When this does occur, the NUT Project (2.7) has been able to settle the matter without difficulty in the project mailing list. It is therefore proposed to not burden IANA with this namespace management and to continue with the current process in which the project in its mailing list acts as a Working Group.¶
The Commands, Responses, Statuses and Variables are currently recorded as follows:¶
Namespace | Recording document | Reference |
---|---|---|
Commands and Responses | This document | Commands (4.2), Responses (4.3) |
(Idem, historical record) | Project Developer Guide Ch 9 | Developer Guide [devguide] |
Statuses | This document | Statuses (5.1) |
(Idem, historical record) | Source code clients/status.h
|
GitHub repository [gitstats] |
Variables | Source code file docs/nut-names.txt
|
GitHub repository [gitvars] |
7.2. Port Name and Number used to Manage UPS Units
See the IANA Registry [Registry] for the latest situation.¶
7.2.1. Port nut/3493
In 2002 IANA assigned port nut/3493 to project lead Russell Kroll, and updated the assignment to the NUT Project (2.7) itself in 2020.¶
7.2.2. Port ups/401
In 2008 IANA assigned ups/401
"Uninterruptible Power Supply" to Mr. Charles Bennett as both
assignee and contact. We have been unable to find any protocol
document or other published activity report for this port other than
the One Windows Trojan. Mr. Bennett himself died in 2015,
see obituary [Bennett]. Since his email address
was registered by IANA as bennettc@ohio.edu
it is possible
that the University of Ohio is a successor in interest. The editor
tried to contact the IT support department of the university by email
and telephone but was rejected.
Ed: My non-contact was Mr. Keith Brock, IT Support Senior
Specialist, brock@ohio.edu +1 740 597 2136¶
7.2.3. NUT Project Requirement
The NUT Project (2.7) needs to address the current weak security (6.3) of UPS management deployments, for example¶
- by implementing the "shim" technique (Figure 7) in section (6.4) for providing secure access to the Attachment Daemon (2.1),¶
- or by providing a choice of ports through which an Attachment Daemon (2.1) may receive commands: one for "legacy" traffic, the other for fully secured traffic.¶
The project needs a second registered port. Since ports are a
limited resource, it would be better to re-use an existing port rather
than request a new one, and the project is interested in using
existing port ups/TBD1
. Let's look more closely at this:¶
- The port name "ups" satisfies the Principle of Least Surprise. It is not surprising for a port called "ups" to be used to manage UPSs. It is unlikely to be used for anything else.¶
- There are no other known users of this port and no other published protocols or usage reports.¶
-
The currently assigned port number 401 is for a system port. The project has no imperative need for such a port; a user port, TBD1, would be sufficient. The Attachment Daemon (2.1) is a system activity, but it can be launched by root and dropped to a non-privileged user perfectly well on a user port.¶
Note: In Unix-like systems a port with a number below 1024 is privileged and requires elevated permissions to manage.¶
- System ports are more likely to attract malicious scans than user ports.¶
- The project does not need to be assigned this port. The need is to be able to use port "ups".¶
8. IANA Considerations
8.1. Port Name ups
: Reference to this Document
The NUT Project (2.7) has a requirement to use a second port (7.2.3), and would like to use port
name ups
as well as port nut
. The project requests
that IANA authorise such use, perhaps by updating
the Service Name and Transport Protocol Port
Number Registry [Registry] for ports
ups
and nut/3493
to include a reference to this
document.¶
UPS management does not need a
system port (7.2.3). If port number 401 were freed and the
name ups
assigned to user port TBD1, that would be equally
effective.¶
The document shepherd is requested to replace the port number
TBD1 by any number that IANA assigns to port name
ups
.¶
8.2. Change of Registrant
The NUT Project (2.7) advises IANA that port ups/401
has no effective registrant (7.2.2). The
project does not have an imperative need to be the registrant but
will accept to become the registrant if IANA deems such change desirable.
Such a change in registrant could be accompanied by an allocation of a
user port number TBD1.¶
9. Implementation Status
This section presents a very short report on the status of the Network UPS tools project¶
- May 1996: The first hack as a cron job.¶
- September 1997: The first server-client code.¶
- March 1998: First public release.¶
- June 1999: Code rewrite with a UPS driver
smartups
, an Attachment Daemon (2.1)upsd
and a simple Management Daemon (2.6).¶ - September 1999: The project became "Network UPS Tools". The
Management Daemon (2.6)
upsmon
supported primary/secondary configurations.¶ - June 2001: Common core for multiple drivers. Arnaud Quette took over the project lead from Russell Kroll.¶
- May 2002: IANA granted port nut/3493. August: release 1.0.0. November: OpenSSL support.¶
- April 2003: The initial set of command and variable names was designed.¶
- March 2016: Version 2.7.4 released, supported over 100 device manufacturers and hundreds of UPS models.¶
- November 2020: Evgeny "Jim" Klimov took over project lead from Arnaud Quette.¶
For a much more detailed history of the NUT Project (2.7) see the User Manual, Appendix J [History]¶
9.1. An Implementation of the Attachment Daemon
The NUT Project (2.7) implemented an Attachment Daemon (2.1) as program upsd
and a set of
hardware specific drivers, all written in K&R C. upsd
supported all of the protocol commands and responses defined by this
document.¶
An experimental program written in Python3 provided
a TLS 1.3 [RFC8446] shim daemon as shown
in figure (7) which ran in front
of upsd
, making it appear that upsd
supported TLS
1.3.¶
9.2. An Implementations of the Management Daemon
There are several examples of a Management Daemon (2.6): the NUT Project (2.7)
provided upsmon
which takes the system shutdown decision when
utility power fails. Further configuration options such as timers
were provided by helper program upssched
.¶
Other programs representing the Management Daemon (2.6):¶
-
upsc
reported the values of the variables (8) defined for a given UPS.¶ -
upsrw
reported on and changed the values of the readable and writable configuration variables (A.2) defined for a given UPS.¶ -
upscmd
reported on and executed the instant action commands (4.2.6) defined for a given UPS.¶ -
UPSmon.py
was an experimental Python3 rewrite ofupsmon
andupssched
which included support for TLS 1.3 [RFC8446].¶
9.3. Inclusion in Software Distributions
The programs upsd
, upsmon
, upssched
,
upsc
, upscmd
and upsrw
have been included
in the package known as "nut" in the package systems of many
distributions: all the major Linux distributions, and Unix
distributions such as OpenBSD and OpenSolaris. A Microsoft Windows
version has been developed but was not maintained.¶
10. Acknowledgments
This document is based on the NUT Project (2.7) documentation [devguide]. The editor acknowledges the work of Charles Lepple, Arjen de Korte, Arnaud Quette, Jim Klimov, Russell Kroll, Manuel Wolfshant, Mark Hansen and many others who contribute to the nut-upsuser [nut-upsuser]. and nut-upsdev [nut-upsdev] mailing lists.¶
The source for this document is marked up using
an SGML DTD [SGML] and an XML meta-DTD as defined
by
HyTime Annex A [HyTimeA].
The sgmlnorm
[sgmlnorm] program generates
XML which program xml2rfc
[RFC7991] uses
to prepare the HTML and text renderings. The editor acknowledges the
help received from Carsten Bormann and Julian Reschke in the xml2rfc
mailing list.¶
The editor thanks Adrian Farrel for advice received during the preparation of this document. Many helpful comments were received from Bart Smit, David Zomaya, Joyce Norris and Ted Mittelstaedt.¶
11. Normative References
- [RFC2119]
- Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
12. Informative References
- [Bennett]
- "Charles Bennett Obituary", Publisher: Jagers and Sons Funeral Home, 24 Morris Ave., Athens OH, <https://www.legacy.com/obituaries/name/charles-bennett-obituary?pid=174356861>.
- [devguide]
- "Network UPS Tools (NUT) Project Developer Guide", <https://networkupstools.org/docs/developer-guide.chunked/ar01s09.html>.
- [Documentation]
- "Network UPS Tools Documentation", <https://networkupstools.org/documentation.html>.
- [gitstats]
- "GitHub Network UPS Tools code repository, status names", <https://github.com/networkupstools/nut/blob/master/clients/status.h>.
- [gitvars]
- "GitHub Network UPS Tools code repository, variable names", <https://github.com/networkupstools/nut/blob/master/docs/nut-names.txt>.
- [History]
- "Network UPS Tools User Manual, Appendix J Project history", <https://networkupstools.org/docs/user-manual.pdf>.
- [HyTimeA]
- "International Standard ISO/IEC 10744 -- Hypermedia/Time-based Structuring Language, Annex A, SGML Extended Facilities", ISO/IEC JTC 1/SC 34 Document description and processing languages, .
- [IEC62351-1]
- "IEC TS 62351-1 Power systems management and associated information exchange -- Data and communications security. Part 1: Communication network and system security -- Introduction to security issues", IEC Technical Specification Reference number IEC/TS 62351-1:2007(E), 35 pages, CHF 205, Technical Committee TC 57 - Power systems management and associated information exchange, , <https://nanopdf.com/download/technical-iec-specification-ts-62351-1_pdf>.
- [Library]
- "GitHub Network UPS Tools, Devices Dumps Library", <https://networkupstools.org/ddl/>.
- [NUT]
- "Network UPS Tools (NUT) Project", <https://www.networkupstools.org>.
- [nut-upsdev]
- "Network UPS Tools (NUT) Project Mailing List for developers", <https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/nut-upsdev>.
- [nut-upsuser]
- "Network UPS Tools (NUT) Project Mailing List for users", <https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/nut-upsuser>.
- [Registry]
- "Service Name and Transport Protocol Port Number Registry", Publisher: IANA, <https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml>.
- [RFC7942]
- Sheffer, Y. and A. Farrel, "Improving Awareness of Running Code: The Implementation Status Section", BCP 205, RFC 7942, DOI 10.17487/RFC7942, , <https://www.rfc-editor.org/info/rfc7942>.
- [RFC7991]
- Hoffman, P., "The "xml2rfc" Version 3 Vocabulary", RFC 7991, , <https://www.rfc-editor.org/info/rfc7991>.
- [RFC8446]
- Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, , <https://www.rfc-editor.org/info/rfc8446>.
- [SGML]
- Goldfarb, Charles F., "The SGML Handbook", ISBN 0-19-853737-9, .
- [sgmlnorm]
- Clark, James., "SGMLNORM An SGML System Conforming to International Standard ISO 8879 -- Standard Generalized Markup Language", <http://www.jclark.com/sp/sgmlnorm.htm>.
- [stunnel]
- Trojnara, Michal., "Stunnel proxy adds TLS encryption functionality to existing clients and servers", <https://www.stunnel.org/>.
Appendix A. Variables
The UPS variables (2.12) represent the abstracted state of the UPS unit. Certain variables represent not only the state of some hardware feature, but also provide tunable values and instant commands (2.5). The full set of variables is recorded in the reference document for variable names [gitvars].¶
The number of variables used in a given deployment depends on the sophistication of the UPS product: this annex shows a typical example of the subset of variables used for a reasonably complete "consumer grade" UPS. The NUT Project (2.7) maintains a large library of the variable subsets [Library] used by different UPS models.¶
Note that successive versions of a given product may add or delete
features causing a change in the subset of variables used. An example
is the removal of ups.delay.start
from a "consumer grade"
UPS. The manufacturer reserves the feature for the "professional"
product.¶
An implementation of a Management Daemon (2.6) acting as a utility program may
provide a listing of the variables available for a given product, for
example utility program upsc
as
included in the NUT package (9.2).¶
The following sections illustrate the use of variables by taking the values associated with a typical product example of a 1600Va 1000W UPS.¶
A.1. Typical UPS Variables
Variable | Typical value | Default description |
---|---|---|
battery.charge |
100 |
"Battery charge (percent of full)" |
battery.charge.low |
20 |
"Remaining battery level when UPS switches to LB (percent)" |
battery.runtime |
1481 |
"Battery runtime (seconds)" |
battery.type |
PbAc |
"Battery chemistry" |
device.mfr |
Example Mfg |
"" |
device.model |
Economy 1600 |
"" |
device.serial |
1234567890 |
"" |
device.type |
ups |
"" |
driver.name |
usbhid-ups |
"Driver name" |
driver.parameter.lowbatt |
37 |
"Driver parameter: <name>" |
driver.parameter.offdelay |
30 |
"Driver parameter: <name>" |
driver.parameter.ondelay |
40 |
"Driver parameter: <name>" |
driver.parameter.pollfreq |
30 |
"Driver parameter: <name>" |
driver.parameter.pollinterval |
2 |
"Driver parameter: <name>" |
driver.parameter.port |
auto |
"Driver parameter: <name>" |
driver.parameter.synchronous |
no |
"Driver parameter: <name>" |
driver.parameter.vendorid |
0999 |
"Driver parameter: <name>" |
driver.version |
2.7.4 |
"Driver version - NUT release" |
driver.version.data |
HID 1.39 |
"" |
driver.version.internal |
0.41 |
"Internal driver version" |
input.transfer.high |
264 |
"High voltage transfer point (V)" |
input.transfer.low |
184 |
"Low voltage transfer point (V)" |
outlet.1.desc |
PowerShare Outlet 1 |
"Outlet description" |
outlet.1.id |
2 |
"Outlet system identifier" |
outlet.1.status |
on |
"Outlet switch status" |
outlet.1.switchable |
no |
"Outlet switch ability" |
outlet.2.desc |
PowerShare Outlet 2 |
"Outlet description" |
outlet.2.id |
3 |
"Outlet system identifier" |
outlet.2.status |
on |
"Outlet switch status" |
outlet.2.switchable |
no |
"Outlet switch ability" |
outlet.desc |
Main Outlet |
"Outlet description" |
outlet.id |
1 |
"Outlet system identifier" |
outlet.power |
25 |
"" |
outlet.switchable |
no |
"Outlet switch ability" |
output.frequency.nominal |
50 |
"Nominal output frequency (Hz)" |
output.voltage |
230.0 |
"Output voltage (V)" |
output.voltage.nominal |
230 |
"Nominal output voltage (V)" |
ups.beeper.status |
enabled |
"UPS beeper status" |
ups.delay.shutdown |
20 |
"Interval to wait after shutdown with delay command (seconds)" |
ups.delay.start |
30 |
"Interval to wait before (re)starting the load (seconds)" |
ups.firmware |
02 |
"UPS firmware" |
ups.load |
20 |
"Load on UPS (percent of full)" |
ups.mfr |
Example Mfg |
"UPS manufacturer" |
ups.model |
Economy 1600 |
"UPS model" |
ups.power.nominal |
1600 |
"UPS power rating (VA)" |
ups.productid |
ffff |
"Product ID for USB devices" |
ups.serial |
000000000 |
"UPS serial number" |
ups.status |
OL |
"UPS status" |
ups.timer.shutdown |
0 |
"Time before the load will be shutdown (seconds)" |
ups.timer.start |
0 |
"Time before the load will be started (seconds)" |
ups.vendorid |
0999 |
"Vendor ID for USB devices" |
A.2. Typical UPS Readable and Writable Variables
Some of the features of a UPS are represented by
variables which may be tuned by the user. The following variables are
typical of such tunable features. The precise list depends on the
model of UPS. An implementation of a Management Daemon (2.6) acting as a utility
program may provide a listing of the variables available, as well as
acting on them, for example utility
program upsrw
as included in the
NUT package (9.2).¶
Variable | Typical value | Default description provided as response to the command GET DESC
|
---|---|---|
battery.charge.low |
20 |
"Remaining battery level when UPS switches to LB (percent)"
|
input.transfer.high |
264 |
"High voltage transfer point (V)"
|
input.transfer.low |
184 |
"Low voltage transfer point (V)"
|
outlet.1.desc |
PowerShare Outlet 1 |
"Outlet description"
|
outlet.2.desc |
PowerShare Outlet 2 |
"Outlet description"
|
outlet.2.switchable |
no |
"Outlet switch ability"
|
outlet.desc |
Main Outlet |
"Outlet description"
|
outlet.power |
25 |
"Description unavailable"
|
output.voltage.nominal |
230 |
"Nominal output voltage (V)"
|
ups.delay.shutdown |
20 |
"Interval to wait after shutdown with delay command (seconds)"
|
ups.delay.start |
30 |
"Interval to wait before (re)starting the load (seconds)"
|
A.3. Typical UPS Instant Commands
Some of the features of a UPS are actions known
as instant commands (2.5) which may be
ordered by the user. The following variables represent such instant
commands. The precise list depends on the model of UPS. An
implementation of a Management Daemon (2.6) acting as a utility program may provide a
listing of the variables available, as well as acting on them, for
example utility program upscmd
as
included in the NUT package (9.2).¶
Command | Meaning |
---|---|
beeper.disable |
Disable the UPS beeper |
beeper.enable |
Enable the UPS beeper |
beeper.mute |
Temporarily mute the UPS beeper |
load.off |
Turn off the load immediately |
load.off.delay |
Turn off the load with a delay (seconds) |
load.on |
Turn on the load immediately |
load.on.delay |
Turn on the load with a delay (seconds) |
shutdown.return |
Turn off the load and return when power is back |
shutdown.stayoff |
Turn off the load and remain off |
shutdown.stop |
Stop a shutdown in progress |
Appendix B. The Shutdown Story for System and UPS
This appendix provides background material helpful for a general understanding of the relation between system and UPS. It does not define any feature of the command-response protocol.¶
We consider the steps involved in the shutdown and restart of a long-running unattended server protected by a single UPS. The Management Daemon (2.6) runs in the server as shown in figure Figure 9.¶
-
Wall power on -- The system runs normally. Every 5 seconds, variable
ups.status
reportsOL
. -- Days, weeks, months go by...¶ -
Winter storm. Tree falls on power lines. Wall power fails
-- The server remains operational running on the UPS battery. The
Management Daemon (2.6) polls the Attachment Daemon (2.1), and detects status change
OL
->OB
.¶ - The Management Daemon (2.6) logs warning messages. The server is still operational running on the UPS battery. -- Minutes go by...¶
- The battery discharges below the level specified by variable
battery.charge.low
. The server remains operational, but the UPS battery will not last much longer. The Management Daemon (2.6) polls the Attachment Daemon (2.1), and detects status changeOB
->OB
+LB
.¶ - The Management Daemon (2.6) logs the low battery event.¶
- The Management Daemon (2.6) decides to call for a system shutdown and issues the system shutdown command.¶
-
The operating system's shutdown process takes over. During the system shutdown, a NUT Project (2.7) specific script or an equivalent systemd service unit runs the command
upsdrvctl shutdown
. This tells the UPS that it is to shut down N seconds later where the default is N=20. Note that the "shutdown" of a UPS removes power from the outlet sockets, but may not turn the UPS off completely. A delayed shutdown is sometimes audible, and the characteristic beeping of the UPS stops.¶ - The system shuts down and powers down, hopefully before the N=20 seconds have passed.¶
-
N seconds after item 7 -- The UPS shuts down, i.e., it turns off its
outlet sockets when N=20 seconds have passed. With some UPS units,
there is an audible "clunk". The absence of AC power to the protected
system for a sufficient time has the effect of resetting the server's
BIOS options, and in particular the option "Restore power on AC
return". This BIOS option will be needed to restart the box. How long
is a sufficient time for the BIOS to reset? This depends very much on
the box. Some need more than 10 seconds. What if wall power returns
before the "sufficient time" has elapsed? The UPS unit should be able
to wait a configurable time with default 30 seconds. These two timers
start from the moment the UPS receives the
upsdrvctl shutdown
command. -- Minutes, hours, days go by...¶ - Some time later, maybe much later, wall power returns -- The UPS reconnects it's outlets to send power to the protected system.¶
- The system BIOS option "Restore power on AC return" has hopefully been selected and the system powers up. The bootstrap process of the operating system begins.¶
- The operating system starts the Attachment Daemon (2.1) and the Management Daemon (2.6). The Attachment Daemon (2.1)
starts the Driver (2.3) and scans the UPS. The UPS status becomes
OL
+LB
.¶ - After some time, the battery charges above
the
battery.charge.low
threshold and the Attachment Daemon (2.1) declares the status changeOL
+LB
->OL
. We are now back in the same situation as 1 above.¶
Appendix C. Technical Terms: Historical Differences
This appendix lists the major differences between the technical terms used in this document and those used in version 2.7.4 of the NUT Project (2.7).¶
Term in NUT 2.7.4 | Term in this document |
---|---|
ALREADY-LOGGED-IN | ALREADY-ATTACHED (Table 3) |
ALREADY-SSL-MODE | TLS-ALREADY-ENABLED (Table 3) |
LOGIN |
ATTACH (4.2.1)
|
LOGOUT |
DETACH (4.2.2)
|
Master | Primary (2.8) |
NETVER |
PROTVER (4.2.10)
|
NUMLOGINS |
NUMATTACH (4.2.4.3)
|
Slave | Secondary (2.9) |
Appendix D. Change Log
This section is to be removed before publishing as an RFC.¶
Ed: To be removed on publication.¶
D.1. Changes in Version 01
D.2. Changes in Version 02
- Extended acknowledgments.¶
- Added reference to possible use of RFC1628 between driver and Attachment Daemon (2.1).¶
- Clarified response to command
LIST CLIENT
.¶
D.3. Changes in Version 03
- Clarified description of Attachment Daemon (2.1).¶
- Added Implementation status section as recommended by RFC 7942 [RFC7942].¶
- Rewrote Section 7.2.3, Paragraph 1.¶
- Clarified Appendix A, Paragraph 1 as being merely an example of variables used for a specific UPS product.¶
- Added definition of
<upsname>
in Section 4.2, Paragraph 1.¶
D.4. Changes in Version 04
There are many changes in this version following the ISE review.
See reply to ISE review: http://rogerprice.org/NUT/ISE-comments-2021-06-14.reply.html
Among other changes are:¶
- Section (7) becomes "Codepoint Management".¶
- Editorial cleanup. All
<aside>
elements labelled as notes.¶ - Added implementation note to Section 4.2.7, Paragraph 1.¶
- Error message
ALREADY-SSL-MODE
becomesALREADY-TSL-ENABLED
.¶ - Added error message
TSL-NOT-ENABLED
.¶ - Typo in clause UPS status (Section 2.11, Paragraph 1).¶
- Removed all reference to use of RFC1628 between driver and Attachment Daemon (2.1).¶
- In Section 4.2, Paragraph 1 field [:<port>] is always available in <upsname>¶
- Added technical term administrative user (2.2).¶
- Added appendix Technical terms: Historical differences (C)¶
- Added table of "successful" responses: Response when command succeeds (4.3.1)¶
- Three commands change name
LOGIN
->ATTACH
(4.2.1),LOGOUT
->DETACH
(4.2.2) andNUMLOGINS
->NUMATTACH
(4.2.4.3).¶ - Error message
ALREADY-LOGGED-IN
becomesALREADY-ATTACHED
.¶
D.5. Changes in Version 05
This version includes changes made following comments by the reviewers.¶
- Abstract: Change "takes" -> "automates".¶
- Abstract: Change "Current practice" -> "Current practice when this text was written".¶
- Abstract: Change "leads to" -> "risks".¶
- Section (1.1), Added sentence on use of "public power supply".¶
- Section (1.2), Change "shutting down..." -> "performing a managed shutdown of unattended..."¶
- Section (1.4) added link to NUT documentation.¶
- Section (2) added "They are listed in alphabetical order."¶
- Section (2.1) Change "talks to the UPS" -> "retrieves status from the UPS and sends commands to it".¶
-
Section (2.1) Change "... launched
as system user root and drops privilege ..." -> "... launched as
system user root to allow direct access to the hardware
(e.g.
/proc
,/dev
). For better security, the daemon then drops privilege ..."¶ - Section (2.2) Change "Management Daemon (2.6) users." -> "Management Daemon (2.6) users which authenticate to the attachment daemon with basic credentials (username and password)."¶
- Section (2.2) Change "... and are defined by a file in the ..." -> "... and are listed in a text file which is read by the ...".¶
- Section (2.2) Added link to Section 6.5.1, Paragraph 1.¶
- Section (2.3) Change "specific to the hardware" -> "specific to the UPS hardware"¶
- Section (2.5) Change "causes the hardware" -> "is passed to the driver and sent to the hardware".¶
- Section (2.5) Change "to immediately" -> "without any configured delay to".¶
- Section (2.6) Change "the system reaction to power loss." -> "orchestrating system-wide actions after a power event."¶
- Section (2.7) Title "NUT Project" -> "NUT Software Project".¶
- Section (2.8) Change "the system to which the data lead is connected" -> "the computer running the driver".¶
- Section (2.9) Replaced and clarified "data lead" not present with secondaries.¶
- Section (2.10) Change "may open a session" -> "may initiate a TCP session".¶
- Section (2.11) Change "are considered fundamental and are" -> "MUST be".¶
- Section (2.11) Change "other statuses depend" -> "other statuses are OPTIONAL and depend".¶
- Section (2.12) Change "The features" -> "The metrics and identifiers".¶
- Section (2.12) Change "current value attached to that feature" -> "value representing that metric or identifier".¶
- Section (2.12) Added a note: "Note: Some variables are constants, e.g. battery type, manufacturer."¶
- Section (3) Rewrote paragraph to clarify "the Attachment Daemon and the Management daemon which act as server and client respectively."¶
- Section (3) Change "run the Attachment Daemon (2.1)." -> "run the Attachment Daemon (2.1), thereby effectively creating a network attached UPS running a standard protocol."¶
-
Figure (4) In the note:
replaced "but if the UPS had status OB the Secondary shuts down." by
"but if the UPS had status
OB
the Secondary may choose to shut down as a precaution."¶ - Section (4.1) Added scholarly historical note.¶
- Section (4.2) Change "of the port" -> "of the TCP port".¶
- Section (4.2.1) Change "the count is 1 (the Primary (2.8)) + the number of Secondaries (2.9)" -> "the count is 1 for the primary + the number of secondaries". Change "a trio of" to "three".¶
- Section (4.2.3) Clarify that "FSD" means "Forced Shutdown".¶
- Section (4.2.3) Change "only to a high-level" -> "only to a privileged".¶
- Section (4.2.4) Added prefix GET to all the subcommands.¶
- Section (4.2.7) Added prefix LIST to all the subcommands.¶
- Section (4.2.7) Change "common container" -> "common".¶
- Section (4.2.7) Change "then go off and wait for the response" to "wait".¶
-
Section (4.2.10) Added note
differentiating
PROTVER
(4.2.10) andVER
(4.2.14).¶ - Section (4.2.11) Changed "and the UPS model." -> "and the UPS model. Some variables are read-only due to the design of the UPS or its driver."¶
- Section (4.2.12) Changed "The choice of TLS version is a matter for site security policy and is not specified in this document." -> "The parameters and versions of cryptographic libraries are those of the Attachment Daemon's underlying OS and are outside the scope of this document."¶
-
Section (4.2.13) Change "provides
facilities to limit access to the UPS unit(s) to which it is
attached." -> "limits access to clients whose credentials match those
in the file
upsd.users
. There is no anonymous access."¶ -
Section (4.2.14) Added note
differentiating
VER
(4.2.14) andPROTVER
(4.2.10).¶ - Section (5.1) Change "public supply", "wall power" and "input supply" -> "input power supply", nine places.¶
- Section (5.1) Remove notes from CHRG and DISCHARG.¶
- Section (5.1) OB: Removed "offline".¶
- Section (5.2) Change "deduces" -> "detects".¶
- Section (5.2) Change "valuable resources" -> "compute and network resources" .¶
- Section (5.2) Change "will not have up-to-date information about the UPS status" -> "risks missing short-lived changes in the UPS status"¶
- Section (6.4) After "imposed by a wave of the hand" added "it cannot be implemented quickly and without impact to many deployed systems".¶
- Section (6.4.3) Added section.¶
- Section (6.4.4) Added section with figure.¶
- Section (7.2.3) Added "Note: In Unix-like systems a port with a number below 1024 is privileged and requires elevated permissions to manage."¶
- Section (8.2) Change "but accepts" -> "but will accept".¶
- Appendix (A) Change "domestic" -> "consumer grade".¶
- Appendix (B) item (7) Change Note that the "shut down" of a UPS does not turn the UPS off completely. It disconnects the outlet sockets. Such a delayed shutdown is audible since the characteristic beeping of a UPS stops. -> Note that the "shutdown" of a UPS removes power from the outlet sockets, but may not turn the UPS off completely. A delayed shutdown is sometimes audible, and the characteristic beeping of the UPS stops.¶