'\" t
.\"     Title: dummy-ups
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 06/21/2026
.\"    Manual: NUT Manual
.\"    Source: Network UPS Tools 2.8.5
.\"  Language: English
.\"
.TH "DUMMY\-UPS" "8" "06/21/2026" "Network UPS Tools 2\&.8\&.5" "NUT Manual"
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.SH "NAME"
dummy-ups \- Driver for multi\-purpose UPS emulation or relay
.SH "SYNOPSIS"
.sp
\fBdummy\-ups\fR \-h
.sp
\fBdummy\-ups\fR \-a \fIUPS_NAME\fR [\fIOPTIONS\fR]
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
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.ps +1
\fBNote\fR
.ps -1
.br
.sp
This man page only documents the specific features of the \fBdummy\-ups\fR driver\&. For information about the core driver, see \fBnutupsdrv\fR(8)\&.
.sp .5v
.RE
.SH "DESCRIPTION"
.sp
This program is a multi\-purpose UPS emulation tool\&. Its general behavior depends on the running mode: "dummy" ("dummy\-once" or "dummy\-loop"), or "repeater"\&.
.SS "Dummy Mode"
.sp
In this mode, \fBdummy\-ups\fR looks like a standard NUT device driver to \fBupsd\fR(8) and allows one to change any value for testing purposes\&.
.sp
It is both interactive, controllable through the \fBupsrw\fR(8) and \fBupscmd\fR(8) commands (or equivalent graphical tool), and batchable through script files\&.
.sp
It can be configured, launched and used as any other "real" NUT driver\&. This mode is mostly useful for development and testing purposes\&.
.if n \{\
.sp
.\}
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.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
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.ps +1
\fBNote\fR
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.sp
See below about the differences of dummy\-once vs\&. dummy\-loop modes \(em the former may be more suitable for "interactive" uses and tests\&.
.sp .5v
.RE
.SS "Repeater Mode"
.sp
In this mode, \fBdummy\-ups\fR acts as a NUT client, simply forwarding data\&.
.sp
This can be useful for supervision purposes\&. This mode can also allow some load sharing between several upsd instances communicating with ultimate NUT clients, with a "central" one using a point\-to\-point communication with the actual UPS or ePDU device\&.
.sp
This arrangement can also help with networked UPSes, whose network management cards can be overwhelmed with a whole farm of servers directly polling SNMP or other networked protocols every few seconds\&.
.SH "IMPLEMENTATION"
.sp
The port specification in ups\&.conf depends on the running mode, and allows the driver to select the right mode of operation\&.
.sp
Since NUT v2\&.8\&.0, the mode specification in ups\&.conf allows users to override the mode of operation which would be otherwise guessed by the driver\&.
.SS "Dummy Mode"
.sp
In this context, port in the ups\&.conf block specifies a "definition file" name for the \fBdummy\-ups\fR to read data from\&. This can either be an absolute or a relative path name\&. In the latter case the NUT sysconfig directory (i\&.e\&. /etc/nut, /usr/local/ups/etc, \&...) is prepended\&.
.if n \{\
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.\}
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.it 1 an-trap
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.sp
The "sysconfig" location is built\-in according to configure script arguments, but can be tuned at run time by NUT_CONFPATH environment variable\&. See the tests/NIT/nit\&.sh script in NUT sources, which heavily relies on this driver, for more examples\&.
.sp .5v
.RE
.sp
Since NUT v2\&.8\&.0 two aspects of this mode are differentiated:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
dummy\-once
reads the specified file once to the end (interrupting for
TIMER
lines, etc\&.) and does not re\-process it until the filesystem timestamp of the data file is changed; this reduces run\-time stress if you test with a lot of dummy devices, and allows use/test cases to
upsrw
variables into the driver instance \(em and they remain in memory until the driver is restarted (or the file is touched or modified);
.sp
Since NUT v2\&.8\&.0
dummy\-once
is assigned by default to files with a
*\&.dev
naming pattern\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
dummy\-loop
reads the specified file again and again, with a short sleep between the processing cycles; for sequence files using a
TIMER
keyword (see below), or for use/test cases which modify file contents with external means, this allows an impression of a device whose state changes over time\&.
.sp
Before NUT v2\&.8\&.0 this was the only aspect, so a simple
dummy
mode value maps to this behavior for backwards compatibility\&.
.sp
Since NUT v2\&.8\&.0
dummy\-loop
is assigned by default to files with a
*\&.seq
naming pattern, and
dummy
is assigned by default to files with other naming patterns that the driver could not classify\&.
.RE
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
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\fBNote\fR
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.sp
Said defaulting based on filename pattern can break third\-party test scripts which earlier expected *\&.dev files to work as a looping sequence with a TIMER keywords to change values slowly\&. Now such files should get processed to the end once\&.
.sp
Specify mode=dummy\-loop driver option or rename the data file used in the port option for legacy behavior\&.
.sp
Use/Test\-cases which modified such files content externally should not be impacted\&.
.sp .5v
.RE
.sp
For instance:
.sp
.if n \{\
.RS 4
.\}
.nf
        [dummy1]
                driver = dummy\-ups
                port = evolution500\&.seq
                desc = "dummy\-ups in dummy\-loop mode"

        [dummy2]
                driver = dummy\-ups
                port = epdu\-managed\&.dev
                desc = "dummy\-ups in dummy\-once mode"
.fi
.if n \{\
.RE
.\}
.sp
This definition file, specified by the port argument in the example above, is generally named something\&.dev or something\&.seq\&. It contains a list of all valid variables and associated values (you can later use upsrw only to modify values of these variables), and has the same format as an \fBupsc\fR(8) data dump (<varname>: <value>)\&. This means you can easily create definition files from an existing UPS using upsc > file\&.dev\&.
.sp
Note that the Network UPS project provides an extensive DDL (Devices Dumps Library) with files which can be used for modelling real devices\&. Entries for the DDL library are best prepared with the tools/nut\-ddl\-dump\&.sh script from NUT sources instead of plain upsc, to provide some additional data points from other NUT clients as well\&.
.sp
The file can also be empty, in which case only a basic set of data is available: device\&.*, driver\&.*, ups\&.mfr, ups\&.model, ups\&.status as filled by the driver itself\&.
.sp
Some sample definition files are available in the data directory of the NUT source tree, and generally in the "sysconfig" or "share" directory of your system distribution\&.
.sp
Since \fBdummy\-ups\fR will usually loop on reading this file, you can dynamically modify it with some external process to "interact" with the driver\&. This will avoid message spam into your system log files, if you are using NUT default configuration\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
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\fBNote\fR
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.sp
By default since NUT v2\&.8\&.0, it will not loop on files in dummy\-once mode, e\&.g\&. those with a \&.dev extension, unless their timestamp changes\&.
.sp .5v
.RE
.sp
You can also use the TIMER <seconds> instruction to create scheduled event sequences (such files are traditionally named with the \&.seq extension)\&. For example, the following sequence will loop on switching ups\&.status between "OL", "OB" and "OB LB" every minute:
.sp
.if n \{\
.RS 4
.\}
.nf
ups\&.status: OL
TIMER 60
ups\&.status: OB
TIMER 60
ups\&.status: OB LB
TIMER 60
.fi
.if n \{\
.RE
.\}
.sp
It is wise to end the script for dummy\-loop mode with a TIMER keyword\&. Otherwise dummy\-ups will directly go back to the beginning of the file and, in particular, forget any values you could have just set with upsrw\&.
.sp
Note that to avoid CPU overload with an infinite loop, the driver "sleeps" a bit between file\-reading cycles (currently this delay is hardcoded to one second), independently of (and/or in addition to) any TIMER keywords and possibly the common pollinterval setting\&.
.sp
Another, more recently introduced instruction is ALARM, which allows the simulation of UPS alarms in much the same way they would be raised by real driver implementations\&. Modern drivers decouple alarm states from the ups\&.status variable, and raising ALARM by setting it as a status token is discouraged in favor of using modern, common functions for raising alarms within the driver code\&.
.sp
The ALARM instruction is intended to simulate this behavior as closely as possible\&. The value following an ALARM instruction is treated as the alarm message and is eventually published as the ups\&.alarm variable, with the ALARM token also set in ups\&.status by internal driver mechanisms, rather than by directly manipulating the variable\&. Multiple ALARM instructions will have their messages combined into the ups\&.alarm variable, just as would happen with real driver logic\&.
.sp
Conversely, any ALARM instruction on its own will clear active alarm states\&. See below for an example of setting and resetting alarms:
.sp
.if n \{\
.RS 4
.\}
.nf
ALARM [UPS too warm to charge]
ALARM [UPS circuit is overheating]
TIMER 5
ALARM
TIMER 5
ALARM [UPS too cold to charge]
.fi
.if n \{\
.RE
.\}
.SS "Repeater Mode"
.sp
In this context, port in the ups\&.conf block is the name of the target UPS, using the NUT format, i\&.e\&.:
.sp
.if n \{\
.RS 4
.\}
.nf
<upsname>@<hostname>[:<port>]
.fi
.if n \{\
.RE
.\}
.sp
For instance:
.sp
.if n \{\
.RS 4
.\}
.nf
[repeater]
        driver = dummy\-ups
        port = ups1@remotehost
        desc = "dummy\-ups in repeater mode"
.fi
.if n \{\
.RE
.\}
.sp
Unlike UPS specifications in the rest of NUT, the @hostname portion is not optional \(em it is the @ character which enables Repeater Mode\&. To refer to an UPS on the same host as \fBdummy\-ups\fR, use port = upsname@localhost\&.
.sp
Note that to avoid CPU overload with an infinite loop, the driver "sleeps" a bit between data\-requesting cycles (currently this delay is hardcoded to one second), so propagation of data updates available to a remote upsd may lag by this much\&.
.sp
Beware that any error encountered at repeater mode startup (e\&.g\&. when not all target UPS to be repeated or their upsd instances are connectable yet) will by default cause the \fBdummy\-ups\fR driver to terminate prematurely\&. This behaviour can be changed by setting the repeater_disable_strict_start flag, making such errors non\-fatal\&.
.SH "INTERACTION"
.sp
Once the driver is loaded in dummy mode, you can change any variables, except those of the driver\&.* and server\&.* collections\&. You can do this by either editing the definition file, or use the \fBupsrw\fR(8) and \fBupscmd\fR(8) commands\&.
.sp
Note that in simulation mode, new variables can be added on the fly, but only by adding these to the definition file (and waiting for it to be re\-read)\&. That is, the driver should not allow to define a new variable via upsrw\&.
.sp
Conversely, if you need to remove a variable (such as transient ones, like ups\&.alarm), simply update these by setting an empty value\&. As a result, they will get removed from the data\&.
.sp
In repeater mode, the driver acts according to the capabilities of the UPS, and so supports the same instant commands and settable values\&.
.SH "BACKGROUND"
.sp
Dummy Mode was originally written in one evening to replace the previous \fIdummycons\fR testing driver, which was too limited, and required a terminal for interaction\&.
.sp
\fBdummy\-ups\fR is useful for NUT client development, and other testing purposes\&.
.sp
It also helps the NUT Quality Assurance effort, by automating some tests on the NUT framework and the NIT (NUT Integration Test suite)\&. See the tests/NIT/nit\&.sh script in NUT sources, which heavily relies on this driver, for more examples\&.
.sp
It now offers a repeater mode\&. This will help in building the Meta UPS approach, which allows one to build a virtual device, composed of several other devices (either UPS, PDUs), or perhaps represent the same device which supports several communication protocols and different media (Serial, USB, SNMP\&...)
.SH "BUGS"
.sp
Instant commands are not yet supported in Dummy Mode, and data need name/value checking enforcement, as well as boundaries or enumeration definition\&.
.SH "CAVEATS"
.sp
If you use service management frameworks like systemd or SMF to manage the dependencies between driver instances and the data server, and some of these drivers are dummy\-ups in repeater mode representing data from another driver running on the same system, then you may have to set up special dependencies (e\&.g\&. with systemd "drop\-in" snippet files) to allow your nut\-server to start after the "real" device drivers and before such repeater drivers (without a responding server, they would fail to start anyway)\&. This may also need special care in upsd\&.conf and/or ups\&.conf files to not block the system start\-up for too long while the repeater driver has not started\&.
.SH "AUTHOR"
.sp
Arnaud Quette
.SH "SEE ALSO"
.sp
\fBupscmd\fR(8), \fBupsrw\fR(8), \fBups.conf\fR(5), \fBnutupsdrv\fR(8)
.SS "Clone drivers:"
.sp
The "repeater" mode of \fIdummy\-ups\fR driver is in some ways similar to the \fIclone\fR and \fIclone\-outlet\fR drivers, which sit on top of another driver socket (or named Windows pipe) locally, and allow users to group clients to a particular outlet of a device and deal with this output as if it were a normal UPS\&. Notably, in this mode the \fIdummy\-ups\fR driver is a client to the networked NUT protocol and can relay information of local or remotely served devices, and requires a running NUT data server \fIupsd\fR to represent the "real" device for this to work\&.
.sp
\fBclone\fR(8), \fBclone-outlet\fR(8)
.SS "Internet Resources:"
.sp
The NUT (Network UPS Tools) home page: https://www\&.networkupstools\&.org/historic/v2\&.8\&.5/