iflandown
iflandown runs commands after the wired LAN link is down for a given amount of time.
All/most linux devices should work. Tested on amd64, Raspberry Pi, odroid
Why
You can use iflandown to avoid filesystem corruption in your rapsberry Pis, when they are connected to an Uninterruptible Power Supply (UPS). iflandown can safely stop the programs running and shutdown the Pi before it runs beyond the UPS time limit, avoiding thus risk of sd card corruption, in case of a too long power outage.
For this to work, the home router shouldn't be protected by the UPS, as it serves as the detection feature.
How it works
iflandown checks each minute the LAN ethernet interfaces in /sys/class/net/%s/carrier to register the state of the link.
If a minimum of uptime minutes Window is not reached inside a defined period of time Period, iflandown executes the configured commands.
Usage
Edit the iflandown.toml file with your preferences:
# The past period of time, starting each minute, that is considered to search
# for at least `Window` minutes of LAN (ethernet) uptime
#
# It is measured in minutes.
#
# iflandown will also wait this time before starting to make decisions.
#
# This number of minutes should match roughly the capacity of your UPS to
# serve your devices after a power outage.
Period = 30
# The minimum number of minutes in the `Period` of time that are necessary to
# have been "up" in order to avoid the sequence of commands to run.
Window = 5
# The commands to run
#
# Separate arguments from the main command and include full paths
#
# sudo commands are possible
Commands = [["ls", "-alrt"], ["sudo", "/bin/systemctl", "stop", "myservice"]]
And run the command in the same directory as the iflandown.toml file:
iflandown
To run the commands without checks (to test the commands, permissions), run:
iflandown --nocheck
systemd service
There is also a systemd service file to run iflandown as a service. Just change in the file the user name <user>
Run commands as root without passwords
To let iflandown run commands with sudo and no password, add one line in the /etc/sudoers file for each command and arguments that you configured in iflandown.toml.
For example, to let iflandown stop the systemd service myservice, add this line:
<user> ALL = (root) NOPASSWD: /bin/systemctl stop myservice
Where <user> is the user that will run the iflandown binary/service.
