Ubuntu Manpage: dummy-ups - Driver for multi-purpose UPS emulation

Provided by: nut-server_2.8.1-3.1ubuntu2_amd64

NAME

       dummy-ups - Driver for multi-purpose UPS emulation

NOTE

       This man page only documents the specific features of the dummy-ups driver. For
       information about the core driver, see nutupsdrv(8).

DESCRIPTION

       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".

   Dummy Mode
       In this mode, dummy-ups looks like a standard NUT device driver to upsd(8) and allows one
       to change any value for testing purposes. It is both interactive, controllable through the
       upsrw(1) and upscmd(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.

           Note
           See below about the differences of dummy-once vs. dummy-loop modes — the former may be
           more suitable for "interactive" uses and tests.

   Repeater Mode
       In this mode, dummy-ups 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.

IMPLEMENTATION

The port specification in ups.conf depends on the running mode, and allows the driver to
select the right mode of operation.

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.

Dummy Mode
In this context, port in the ups.conf block defines a file name for the dummy-ups 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.

Since NUT v2.8.0 two aspects of this mode are differentiated:

• 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 — and they remain in
memory until the driver is restarted (or the file is touched or modified);

Since NUT v2.8.0 dummy-once is assigned by default to files with a *.dev naming
pattern.

• 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.

Before NUT v2.8.0 this was the only aspect, so a simple dummy mode value maps to this
behavior for backwards compatibility.

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.

Note
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.

Specify mode=dummy-loop driver option or rename the data file used in the port option
for legacy behavior.

Use/Test-cases which modified such files content externally should not be impacted.

For instance:

[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"

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 upsc(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.

Since dummy-ups 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.

Note
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.

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:

ups.status: OL
TIMER 60
ups.status: OB
TIMER 60
ups.status: OB LB
TIMER 60

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.

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.

Repeater Mode
In this context, port in the ups.conf block is the name of the target UPS, using the NUT
format, i.e.:

<upsname>@<hostname>[:<port>]

For instance:

[repeater]
driver = dummy-ups
port = ups1@remotehost
desc = "dummy-ups in repeater mode"

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
dummy-ups, 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.

Beware that any error encountered at repeater mode startup (e.g. when not all target UPS
to be repeated or upsd instances are connectable yet) will cause dummy-ups driver to
terminate prematurely. This behaviour can be changed by setting the
repeater_disable_strict_start flag, making such errors non-fatal.

INTERACTION

       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 upsrw(1) and upscmd(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.

       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.

       In repeater mode, the driver acts according to the capabilities of the UPS, and so
       supports the same instant commands and settable values.

BACKGROUND

       Dummy Mode was originally written in one evening to replace the previous dummycons testing
       driver, which was too limited, and required a terminal for interaction.

       dummy-ups is useful for NUT client development, and other testing purposes.

       It also helps the NUT Quality Assurance effort, by automating some tests on the NUT
       framework.

       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...)

BUGS

       Instant commands are not yet supported in Dummy Mode, and data need name/value checking
       enforcement, as well as boundaries or enumeration definition.

CAVEATS

       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.

AUTHOR

       Arnaud Quette