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"\&.
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\&. It is both interactive, controllable through the \fBupsrw\fR(1) and \fBupscmd\fR(1) commands (or equivalent graphical tool), and batchable through script files\&. It can be configured, launched and used as any other "real" NUT driver\&. This mode is mostly useful for development and testing purposes\&.
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See below about the differences of dummy\-once vs\&. dummy\-loop modes \(em the former may be more suitable for "interactive" uses and tests\&.
In this mode, \fBdummy\-ups\fR acts as a NUT client, simply forwarding data\&. 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 UPS\&. This arrangement can also help with networked UPSes, whose network management cards can be overwhelmed with a farm of servers directly polling SNMP or other protocols every few seconds\&.
The port specification in ups\&.conf depends on the running mode, and allows the driver to select the right mode of operation\&.
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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\&.
In this context, port in the ups\&.conf block defines a 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\&.
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Since NUT v2\&.8\&.0 two aspects of this mode are differentiated:
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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);
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Since NUT v2\&.8\&.0
dummy\-once
is assigned by default to files with a
*\&.dev
naming pattern\&.
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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\&.
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Before NUT v2\&.8\&.0 this was the only aspect, so a simple
dummy
mode value maps to this behavior for backwards compatibility\&.
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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\&.
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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\&.
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Specify mode=dummy\-loop driver option or rename the data file used in the port option for legacy behavior\&.
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Use/Test\-cases which modified such files content externally should not be impacted\&.
This file 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) dump (<varname>: <value>)\&. So you can easily create definition files from an existing UPS using upsc > file\&.dev\&.
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\&.
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\&.
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\&.
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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\&.
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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\&.
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.RE
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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:
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\&.
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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\&.
Unlike UPS specifications in the rest of NUT, the @hostname portion is not optional \- 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\&.
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\&.
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(1) and \fBupscmd\fR(1) commands\&.
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\&.
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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\&.
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\&.
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\&...)
Instant commands are not yet supported in Dummy Mode, and data need name/value checking enforcement, as well as boundaries or enumeration definition\&.
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\&.
The "repeater" mode of \fIdummy\-ups\fR driver is in some ways similar to the \fIclone\fR driver, which sits on top of another driver socket, and allows users to group clients to a particular outlet of a device and deal with this output as if it were a normal UPS\&.
