Uninterruptable Power Supply

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Revision as of 17:58, 24 June 2010 by Timn (talk | contribs) (Changed for new apcupsd page)

Uninterruptable Power Supply

PythonIcon.png Skill level: Advanced
The instructions on this page may require deviations from standard procedures. A good understanding of linux and Koozali SME Server is recommended.


The primary goal of the Network UPS Tools (NUT) project is to provide reliable monitoring of UPS hardware and ensure safe shutdowns of the systems which are connected.

The default configuration of NUT, will keep your connected systems operational until a critical battery state is reached (ie battery is nearing exhaustion) and then power down your server/equipment in a controlled fashion. See http://www.networkupstools.org/

If you have an APC UPS, see also Uninterruptible_Power_Supply:APC for an alternative to the standard SME Nut implementation

Default Configuration (USB)

The default configuration in SME Server for 'NUT' is set by the configuration database properties

Model  = usbhid-ups
status = disabled
type   = service
Important.png Note:
Absence of a 'Master' property setting defaults the configuration to being a Master setup. That is a UPS connected directly to the server via USB or serial cable is assumed. See later for setting as a Slave.

The default is for NUT to be disabled, that is no UPS connected

Most USB connected UPS's will work with these default settings. If using a USB connection just enable NUT as follows:

config setprop nut status enabled
signal-event post-upgrade
signal-event reboot

If your USB UPS does not work properly OR you have a serial device then follow the Configuration Options below as required.

Configuration Options

Not all UPS's are supported by USB or the usbhid-ups driver. However NUT supports many UPS's and can be configured under SME Server easily.

Serial Connection

  1. Find the configuration details for your model of UPS. Refer to: http://www.networkupstools.org/compat/stable.html and make note of the driver name and upstype number (if any) in the third column.

    Warning.png Warning:
    Always use the serial cable supplied with the UPS. Standard serial cables won't work with a serial UPS and have been known to cause damage to the UPS. Pay particular attention to any references to cable in in the UPS Model column.

  2. From the consol issue the following commands:
    config setprop nut Model <model> 
    config setprop nut Device <device>
    config setprop nut Type <type>
    config setprop nut status enabled 

    <model> and <type> are the driver name and type number found above.
    <device> is the serial port that the UPS is connected to eg. /dev/ttyS0. It also possible to use a more readable symlink. See HowTo on udev - symlinks for details.

    Note: The case of Model, Device and Type.

  3. Check:
    config show nut
  4. Apply changes and restart server:
    signal-event post-upgrade
    signal-event reboot 

    Alternatively, without NUT running or requiring a server reboot:

    expand-template /etc/sysconfig/ups
    expand-template /etc/ups/ups.conf
    expand-template /etc/ups/upssched.conf
    expand-template /etc/ups/upsmon.conf
    expand-template /etc/ups/upsd.users
    expand-template /etc/ups/upsd.conf
    /etc/rc7.d/S38nut start
  5. Confirm server is communicating with UPS:
    upsc UPS@localhost

    Whenever a UPS event occurs Emails are sent to the admin account.

Configuring as a slave

Set configuration values:

config setprop nut SlaveUPS UPS@
config setprop nut Master no

Where is your UPS master, that is the computer that is in direct communication with the UPS. The hostname of that computer may also work.

Apply changes and restart server:

signal-event post-upgrade
signal-event reboot 

Confirm server is communicating with master:

upsc UPS@

Connecting multiple UPS's

To be added http://bugs.contribs.org/show_bug.cgi?id=629

UPS Variables and Commands

In some cases you may wish to modify variables on the actual UPS such as the Low Charge/LOWBATTERY setting. This requires the use of the upsrw command and UPS administrative privileges.

You may also want to control the UPS directly from the command line by issuing UPS commands. This requires use of the upscmd command and UPS administrative privileges.

Warning.png Warning:
In general, the UPS data should be left protected and changes to it or issuing of commands well thought out. If you wish to make data changes or issue commands then the administrative privileges can be enabled as below and should then be disabled.

UPS Administrative Privileges

In order to be able to use upsrw and upscmd it is necessary to have a suitable additional user defined in the upsd.users configuration file.

In order to create a suitable user we will use SME Servers templating system and configuration database. This is based on an original forum thread[1].

First we need to create a suitable custom template directory

mkdir -p /etc/e-smith/templates-custom/etc/ups/upsd.users
cd /etc/e-smith/templates-custom/etc/ups/upsd.users

Create and edit a new file called 'admin' with the following content:

    # create admin user for upsd to allow setting of
    # UPS parameters via upsrw

    $OUT .= "";
    return unless (($nut{AdminUser} || 'disabled') eq 'enabled');
    return unless (($nut{AdminPass} || '') ne '');

    $OUT .= "\n";
    $OUT .= "       [admin]\n";
    $OUT .= "               password  = $nut{AdminPass}\n";
    if ( ($nut{Master} || 'yes') ne 'no') {
       $OUT .= "               allowfrom = localhost\n";
    } else {
       $OUT .= "               allowfrom = localhost localnet\n";
    $OUT .= "               actions   = set\n";
    $OUT .= "               instcmds  = all\n";

Create two new database properties for nut

config setprop nut AdminUser enabled                (This enables the creation of the user in the template above)
config setprop nut AdminPass admin                  (This sets a password for the admin user. Set to whatever you want)

Now, to get upsd to recognise the new user with the required administrative privileges we expand the template and reload the upsd configuration

/sbin/e-smith/expand-template /etc/ups/upsd.users
/usr/sbin/upsd -c reload

Important.png Note:
To disabled the admin user once you have changed the UPS parameters or issued commands as required, issue the commands
config setprop nut AdminUser disabled
/sbin/e-smith/expand-template /etc/ups/upsd.users
/usr/sbin/upsd -c reload

Setting UPS Variables

In order to set UPS variables it is necessary to have enabled a user with administrative privileges as above first.

In the examples below, it is assumed your UPS name is UPS, that it is local, that the administrative user is admin and password admin. You can verify your UPS name via:

upsc -l

To view a complete list of the UPS variables, both informational and modifiable

upsc UPS

To determine the modifiable variables for your UPS, their current settings and their available setting values execute the command:

upsrw UPS

You can now modify the variables you wish using a command similar to the following (Note the order of the arguments is important, and you may need quotes around the value being set, "20"):

upsrw -s battery.charge.low=20 -u admin -p admin UPS

Where the value after -s should be one of the parameters identified by the upsrw ups command. You can of course verify your changes using

upsrw UPS


upsc UPS

After you are done, clean up by disabling the upsd administrative user admin:

Warning.png Warning:
Make sure you understand the meaning or the UPS variables and their available setting options. Verify that your changes meet your intended behaviour!

More information on upsrw can be found at:

- Manual page: man upsrw

- Upsrw examples: MGE UPS Howto

Issuing UPS Commands

In order to issue UPS commands it is necessary to have enabled a user with administrative privileges as above first.

In the examples below, it is assumed your UPS name is UPS, that it is local, that the administrative user is admin and password admin. You can verify your UPS name via:

upsc -l

To view a complete list of available commands for your UPS:

upscmd -l UPS

You can now issue a command to the UPS with similar to the following:

upscmd -u admin -p admin UPS test.battery.start

Where the command test.battery.start is a valid command for your UPS as previously determined by upscmd -l UPS. Depending upon the command issued you may get broadcast messages and emails relating to and confirming what the UPS is doing.

After you are done, clean up by disabling the upsd administrative user admin:

Warning.png Warning:
Before issuing any commands verify what they do for your particular UPS via the relevant documentation and ensure that the command meets your intended behavioural requirement!

Issuing commands could shutdown your server unexpectedly!

Scheduling Events

Shutdown Time Delay Example

By default NUT will issue a shutdown command as soon as it receives a low battery event from the UPS. There may be instances and installation configurations that require a shutdown sooner, or other events with timed or schedules outcomes. See the man pages etc for further info and example situations.

In essence the upsmon program monitors the relevant UPS and for each NOTIFYFLAG event in upsmon.conf takes immediate action as defined. In order to delay or schedule any actions, the events need to be passed to upssched which can set timers and schedule events.

The following changes to standard SME Server NUT configuration will shut down the server a specified time after receiving the "on battery" signal (the example given is for 2 minutes). It assumes you already have an enabled and working NUT configuration and UPS

To create a timed shutdown before the BATTLOW signal is received, it is necessary to configure upssched and have a script handle the UPS events (upsmon cannot do this).

First we need to create a new custom template directory:

mkdir -p /etc/e-smith/templates-custom/etc/ups/upsmon.conf
cd /etc/e-smith/templates-custom/etc/ups/upsmon.conf

Create and edit a new file called 'NOTIFYCMD' with the following content:

NOTIFYCMD /usr/sbin/upssched

Now create another a custom template directory

mkdir -p /etc/e-smith/templates-custom/etc/ups/upssched.conf
cd /etc/e-smith/templates-custom/etc/ups/upssched.conf

Create and edit a new file called '01CONFIG' with the following content:

CMDSCRIPT /sbin/e-smith/nutUPS.cmd
PIPEFN /tmp/upspipe
LOCKFN /tmp/upslock
AT ONBATT * START-TIMER shutdownnow 120     
AT LOWBATT * EXECUTE shutdowncritical

In the above set the line AT ONBATT * START-TIMER shutdownnow 120 to how many seconds after ONBATT signal you want to shut down

Create and edit a new script file at:


Add the following content:

#! /bin/sh
       case $1 in
                       /bin/echo "UPS communications failure on `date`." | /bin/mail -s"UPS communications LOST" admin
                       /usr/bin/wall "UPS communications failure."
                       /bin/echo "UPS communications restored on `date`." | /bin/mail -s"UPS communications restored" admin
                       /usr/bin/wall "UPS communications restored."
                       /bin/echo "UPS communications cannot be established on `date`." | /bin/mail -s"UPS uncontactable" admin
                       /usr/bin/wall "UPS communications cannot be established."
                       /bin/echo "Power failure on `date`." | /bin/mail -s"UPS on battery" admin
                       /usr/bin/wall "UPS on battery. Shutdown in 60 seconds...."
                       /bin/echo "UPS has been on battery for 60 seconds. Starting orderly shutdown on `date`." | /bin/mail -s"UPS on battery for 60 seconds" admin
                       /usr/bin/wall "UPS has been on battery for 60 seconds. Shutting down NOW!!!!"
                       /usr/bin/sudo /sbin/e-smith/signal-event halt
                       /bin/echo "UPS battery level CRITICAL. Starting EMERGENCY shutdown on `date`." | /bin/mail -s"UPS battery CRITICAL" admin
                       /usr/bin/wall "UPS battery level CRITICAL. Shutting down NOW!!!!"
                       /usr/bin/sudo /sbin/e-smith/signal-event halt
                       /bin/echo "Power restored on `date`." | /bin/mail -s"UPS on line" admin
                       /usr/bin/wall "UPS on line. Shutdown aborted."
                       /bin/echo "Unrecognized command: $1"

Nut requires to use sudo for this process to work, so sudo needs configuring to enable the user nut. By default the /etc/sudoers file is not part of the SME Server template system. To workaround this create a custom template directory:

mkdir -p /etc/e-smith/templates-custom/etc/sudoers
cd /etc/e-smith/templates-custom/etc/sudoers

To preserve the content of the orginal /etc/sudoers file copy that into the custom template directory:

cp /etc/sudoers 10sudoers 

Create and edit a new file called '30nut' with the following content:


Then run:

expand-template /etc/sudoers

Finally to complete the process:

signal-event post-upgrade
signal-event reboot

Aditional Information

There are template fragments in /etc/e-smith/templates/etc/ups that control the config files located in /etc/ups. The default settings should be OK for most situations.

By default, NUT is configured for a USB connected UPS in Master mode, but is disabled. When enabled, NUT will monitor the UPS and take various actions when certain notifications are received. This is controlled by the /etc/ups/upsmon.conf file which among other things lists the notifications and the actions to be taken for each. For example an On Battery event is captured by the NOTIFYFLAG ONBATT entry and the following SYSLOG+WALL+EXEC command string. This string tells upsmon to write the event to the System Log, broadcast a message to all users via Wall, and execute the command denoted by the NOTIFYCMD entry.

SME Server sets the NOTIFYCMD to /sbin/e-smith/nutUPS.notify, and this executable file simply sends an email to the SME admin user with a notification of the event.

Apart from the various events that the UPS and upsmon may notify via the NOTIFYFLAGS a Low Battery event will automatically and immediately cause upsmon to issue the SHUTDOWNCMD as defined in upsmon.conf (signal-event halt) and set a flag POWERDOWNFLAG so it knows on future restart that it is a UPS recovery.

For information on configuration parameters:

man ups.conf
man upsd.conf
man upsd.users
man upsmon.conf
man upssched.conf

For general information:

man upsd
man nutupsdrv

The NUT website is here: NUT

From the above references you can glean which configuration setting does what function, etc.

If you want to modify the operation of NUT from the standard configuration, then you should generally modify the NUT config files by creating custom templates, expanding the templates and restarting service. This will ensure modifications survive a future reboot or reconfiguration.

An example of doing this can be found in the forum [2] and in the section above for UPS Administrative Privileges

See also Known Problem - Restarting Nut