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Mirassaqua

Member

Registered: 2020-02-02

Posts: 10

Power supply manager: critical battery level: 2 levels actions

Hello.

On a laptop, the power supply manager enables to set-up an action when the energy in the battery reaches a certain level. For example, at 20% we can choose to: do nothing, ask for action, go to sleep, shutdown the laptop.

My question is: is there a way to set-up a two levels scenario (with battery only, no external power supply plugged-in) ? I would like something like:
– at 20% ask me what to do,
– at 15% shutdown the laptop.
Sometimes, I have to quit my office and I am not in front of my laptop any more. The idea is: if I am here I can choose, if not the laptop shuts down a little bit latter to avoid 0% battery level.

Thank you for your help !

ToZ

Administrator

From: Canada

Registered: 2011-06-02

Posts: 12,341

Re: Power supply manager: critical battery level: 2 levels actions

xfce4-power-manager can only handle one event/action, not two like you're asking for. But you could use udev to trigger one of the events.

For example, set up xfce4-power-manager to shutdown at 15%. Then create the following udev rule:

# Rule for when switching to battery
SUBSYSTEM=="power_supply", ATTR{status}=="Discharging", ATTR{capacity}=="20", RUN+="/usr/bin/systemd-run --machine=toz@.host --user notify-send 'Battery Level Notification' 'Capacity reached'"

...make sure you change "toz" to your username.

Also make sure to reload udev rules:

sudo udevadm control --reload

Depending on the distro you are using, the udev rule could go into /etc/udev/rules.d.

At 20%, you should get a notification. At 15% the computer will shutdown.

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Mirassaqua

Member

Registered: 2020-02-02

Posts: 10

Re: Power supply manager: critical battery level: 2 levels actions

Hello ToZ.

Thank you for your answer.

I am on xubuntu 24.04. I have created a 91-warning-low-battery.rules file inside my /usr/lib/udev/rules.d folder with the content you send me (I changed the user name).
Unfortunately it does not work, even after refreshing udev via sudo udevadm control --reload and sudo udevadm control --reload-rules.

If I run

/usr/bin/systemd-run --machine=mirassaqua@.host --user notify-send 'Warning: battery at low level' 'Battery at 40%'

I get the notification for a very short delay (is there a way to change the display time for this specific notification by the way? I didn't found how to do it).

But the

SUBSYSTEM=="power_supply", ATTR{status}=="Discharging", ATTR{capacity}=="20", RUN+=…

of the rules file does not seem to do the work. I don't know if the event is not taken into account or if its something else…

If you have an idea about it, I take!
Thank you.

Last edited by Mirassaqua (2025-10-28 10:04:43)

ToZ

Administrator

From: Canada

Registered: 2011-06-02

Posts: 12,341

Re: Power supply manager: critical battery level: 2 levels actions

I get the notification for a very short delay (is there a way to change the display time for this specific notification by the way?

Try adding the -t property:

/usr/bin/systemd-run --machine=mirassaqua@.host --user notify-send -t 60000 'Warning: battery at low level' 'Battery at 40%'

....and change the 60000 (milliseconds) to suit.

rules file does not seem to do the work.

What does the following return:

udevadm info -q property -a --path=/sys/class/power_supply/BAT0 | grep -E 'SUBSYSTEM=|{status|capacity}' | grep -v ATTRS

Also, run:

udevadm monitor

...then plug/unplug the laptop and see what is displayed in the output regarding "power_supply".

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Mirassaqua

Member

Registered: 2020-02-02

Posts: 10

Re: Power supply manager: critical battery level: 2 levels actions

Hello Toz.

The tip for the delay works fine and -t 0 enables to have a permanent notification which is very useful for my need. Thanks!

udevadm info -q property -a --path=/sys/class/power_supply/BAT0 | grep -E 'SUBSYSTEM=|{status|capacity}' | grep -v ATTRS

    returns

SUBSYSTEM=="power_supply"
ATTR{capacity}=="35"
ATTR{status}=="Discharging"

    and

udevadm monitor

    returns

monitor will print the received events for:
UDEV - the event which udev sends out after rule processing
KERNEL - the kernel uevent

KERNEL[4872.126783] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV  [4872.144188] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
KERNEL[4872.280420] change   /devices/platform/ACPI0003:00/power_supply/AC (power_supply)
UDEV  [4872.280898] change   /devices/platform/ACPI0003:00/power_supply/AC (power_supply)
KERNEL[4876.901902] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV  [4876.907404] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
KERNEL[4887.431644] change   /devices/platform/ACPI0003:00/power_supply/AC (power_supply)
UDEV  [4887.445599] change   /devices/platform/ACPI0003:00/power_supply/AC (power_supply)

    when I plug and unplug the power supply.

It seems like it's the discharging event that is not taken into account…

Added later 09 min 13 s:
Another point: I have .rules files in the following locations:
– /etc/udev/rules.d   – only few 70-snap.xxx.rules files
– /run/udev/rules.d   – only one 90-netplan.rules file
– /snap/coreXX/YYYY/usr/lib/udev/rules.d   – lots of .rules files
– /var/lib/flatpak/XXX/files/lib/udev/rules.d    – a few .rules files

and
– /usr/lib/udev/rules.d
the one I used since there is numerous .rules files inside related to what seems to be many aspects of the system.
I have chosen the name 91-low-battery-warning.rules because 91- was not used…

Last edited by Mirassaqua (2025-10-28 12:26:43)

ToZ

Administrator

From: Canada

Registered: 2011-06-02

Posts: 12,341

Re: Power supply manager: critical battery level: 2 levels actions

Have you let it fall down to 20% charge - when the notification should be issued? Also look into the journal for around the time the notification should be issued to see if there is an error.

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Mirassaqua

Member

Registered: 2020-02-02

Posts: 10

Re: Power supply manager: critical battery level: 2 levels actions

Hello ToZ.

To perform my tests, I adapt the level of critical battery inside the rules file. For example, if my battery is at 68%, I change

ATTR{capacity}=="66"

and I execute

sudo udevadm control --reload

so that I have few time to wait.

I have looked at the journal. The "%" character issues an error at udevadm control --reload command. Something like

/etc/udev/rules.d/10-local.rules:2 Invalid value "/usr/bin/systemd-run --machine=mirassaqua@.host --user notify-send -t 0 'Warning: battery at low level' 'Battery at 66%'" for RUN (char 119: invalid substitution type), ignoring.

I removed it and I have no issue any more at reload but still no notification… I tried to change the ordre of ATTR{capacity} and ATTR{status} with no more success.

I don't know if there is another way to test the rules… I continue to investigate on my side.
Thank you again.