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This document describes how to install the APC UPS daemon. The main advantage of using an APC UPS (for me) is that it can communicate with your Linux box through either a RS-232 or USB serial connection. In the event of a prolonged power outage, should the APC UPS lose most of its battery capacity, it can tell the Linux box to perform a safe shutdown.

Install the package

Install apcupsd from the official repositories.

Configure APC UPS

The main configuration file for the APC UPS daemon can be found here: /etc/apcupsd/apcupsd.conf

In the following example, the lines of text are changed to support a USB style cable:



UPSTYPE smartups

DEVICE /dev/ttyS0




DEVICE /dev/usb/hiddev[[0-15]]


First, enable and start the systemd service.

systemctl enable apcupsd.service
systemctl start apcupsd.service

Next, wait about a minute and confirm the daemon is running and properly monitoring the battery:

# apcaccess status
APC      : 001,033,0819
DATE     : Sat Mar 05 SOMETIME 2005
HOSTNAME : somehostname
RELEASE  : 3.10.16
VERSION  : 3.10.16 (04 November 2004) unknown
UPSNAME  : somehostname
CABLE    : USB Cable
MODEL    : Back-UPS ES 725
UPSMODE  : Stand Alone
LINEV    : 119.0 Volts
LOADPCT  :  23.0 Percent Load Capacity
BCHARGE  : 100.0 Percent
TIMELEFT :  30.5 Minutes
MBATTCHG : 5 Percent
MINTIMEL : 3 Minutes
MAXTIME  : 0 Seconds
LOTRANS  : 088.0 Volts
HITRANS  : 138.0 Volts
BATTV    : 13.5 Volts
TONBATT  : 0 seconds
CUMONBATT: 0 seconds
STATFLAG : 0x02000008 Status Flag
MANDATE  : 2002-12-02
SERIALNO : QB0249360043
BATTDATE : 2000-00-00
NOMBATTV :  12.0
FIRMWARE : 02.n2.D USB FW:n2

To fully test your setup:

  1. Change TIMEOUT form 0 to 1 in the /etc/apcupsd/apcupsd.conf file.
  2. Remove wall power from the UPS.
  3. Observe that your Linux box powers down, in short order.
  4. Plug the UPS back into the wall.
  5. Power on your Linux box.
  6. Change TIMEOUT from 1 back to 0 in the /etc/apcupsd/apcupsd.conf file.

When everything is ok, all that's left to do is enable the apcupsd service.

Hibernating instead of shutting down

You can make your system hibernate instead of shutting down. First, make sure the system hibernates cleanly. To set up hibernation, look here.

Create the hibernate script

Create this in /usr/local/bin/hibernate as root:

# Hibernate the system - designed to be called via symlink from /etc/apcupsd
# directory in case of apcupsd initiating a shutdown/reboot.  Can also be used
# interactively or from any script to cause a hibernate.

# Do the hibernate
/usr/bin/systemctl hibernate

# At this point system should be hibernated - when it comes back, we resume this script here

# On resume, tell controlling script (/etc/apcupsd/apccontrol) NOT to continue with default action (i.e. shutdown).
exit 99

Make it executable by running:

# chmod +x /usr/local/bin/hibernate

Link the hibernate script for apcupsd to use it

Create a symbolic link from the /etc/apcupsd directory to the script. The result is the apcupd's apccontrol script, in this directory, will call the hibernate script instead of doing the default shutdown action for these operations.

# ln -s /usr/local/bin/hibernate /etc/apcupsd/doshutdown

If you are running apcupsd as a client to another machine running apcupsd as a server and want your machine to hibernate if the sever is shutdown or if communication to the server is lost then you may also wish to add:

# ln -s /usr/local/bin/hibernate /etc/apcupsd/remotedown

Make apcupsd kill UPS power once the hibernate is done

Once the PC has hibernated successfully, it's better for the UPS to be switched off in order to conserver battery charge, and prevent full battery drain. This can be achieved very easily! Create a file /etc/pm/sleep.d/99apc and put the following contents in it

case $1 in
        # See if this is a powerfail situation.                            # ***apcupsd***
        if [ -f /etc/apcupsd/powerfail ]; then                             # ***apcupsd***
        echo                                                               # ***apcupsd***
        echo "APCUPSD will now power off the UPS"                          # ***apcupsd***
        echo                                                               # ***apcupsd***
        /etc/apcupsd/apccontrol killpower                                  # ***apcupsd***
        echo                                                               # ***apcupsd***
        echo "Please ensure that the UPS has powered off before rebooting" # ***apcupsd***
        echo "Otherwise, the UPS may cut the power during the reboot!!!"   # ***apcupsd***
        echo                                                               # ***apcupsd***
        fi                                                                 # ***apcupsd***

Make the script executable by doing:

# chmod +x /etc/pm/sleep.d/99apc

Now you can test your setup.

The desktop environment will also sense the UPS if connected by USB cable

For example, the default KDE setting is to put the computer in sleep if it has been on UPS battery for more than 10 minutes and the mouse has not moved. On many computers this causes a crash. This can be changed from KDE System Settings->Power Management->On battery.

See also