From ArchWiki

This document describes how to install the APC UPS daemon. The APC UPS can communicate with the Linux system 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 the apcupsd package.

Configure APC UPS

The main configuration file for the APC UPS daemon can be found in /etc/apcupsd/apcupsd.conf. The default configuration is for devices connected over a USB cable.


First, enable and 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 from 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 is 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, see Power management/Suspend and hibernate.

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.

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 is common practice to switch off the UPS in order to conserve battery charge and prevent full battery drain. This can be achieved through a power suspend event in systemd.

Create /usr/lib/systemd/system-sleep/ups-kill and put the following contents in it:


case $2 in

  # In the event the computer is hibernating.
    case $1 in

       # Going into a hibernate state.

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

       # Coming out of a hibernate state.

         # If there are remnants from a powerfail situation, remove them.
         if [ -f /etc/apcupsd/powerfail ]; then
           rm /etc/apcupsd/powerfail

         # This may also exist, need to remove it.
         if [ -f /etc/nologin ]; then
           rm /etc/nologin

	 # Restart the daemon; otherwise it may be unresponsive in a
         # second powerfailure situation.
	 systemctl try-restart apcupsd

Make the script executable.

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.

hid-generic : control queue full

If you are using a systemd-based initramfs you might run into the "control queue full" log message happening many times every second. You will want to add hid-generic to you modules and regenerate your initramfs.

See also