Restart system services after an OS update
This guide describes how to use the clr-service-restart tool.
Clear Linux* OS includes a clr-service-restart tool that shows which system daemons require a restart.
clr-service-restart reads various files in the
filesystem provided by the kernel and relies on systemd to
determine which services to restart.
clr-service-restart implements a whitelist to identify which daemons can be restarted. As a system administrator, you can customize the default Clear Linux OS OS whitelist using allow or disallow options for restarting system services. When a software update occurs, clr-service-restart consults the whitelist to see if a service daemon is allowed to be restarted or not.
clr-service-restart has three basic options: allow, disallow, and default.
The allow option identifies a daemon to restart after an OS software
update. The clr-service-restart daemon creates a symlink in
/etc/clr-service-restart as a record. The example below tells
clr-service-restart to restart the tallow daemon after an
OS software update.
sudo clr-service-restart allow tallow.service
The disallow option tells clr-service-restart not to
restart the specified daemon even if the OS defaults permit the daemon to be
restarted. The clr-service-restart daemon creates a symlink in
/etc/clr-service-restart that points to
/dev/null as a
record. The example below tells clr-service-restart not to
restart the rngd daemon after an OS software update.
sudo clr-service-restart disallow rngd
The default option makes clr-service-restart revert back
to the OS defaults and delete any symlink in
The example below tells clr-service-restart to restart rngd
automatically again, because rngd is whitelisted for automatic service
restarts by default in Clear Linux OS.
sudo clr-service-restart default rngd
clr-service-restart works in the background and is invoked with swupd automatically. Review the journal output to verify that services are restarted after an OS software update.
If you pass both options (-a and -n) described below, clr-service-restart displays a complete list of system services that require a restart. Use both options to verify that all desired daemons are restarted.
The -n option makes clr-service-restart perform no restarts. Instead it displays the services that could potentially be restarted. When used, clr-service-restart outputs a list of messages showing:
- Which service needs a restart.
- What unit it is.
- Why it needs a restart.
- Which command is required to restart the unit.
The -a option makes clr-service-restart consider all system services, not only the ones that are whitelisted. Because the default whitelist in Clear Linux OS is relatively short, you can use this option to restart all impacted services when you log in on the system.
In the example below, clr-service-restart is invoked with both the -a and -n options, which displays a complete list of system services that require a restart.
sudo clr-service-restart -a -n
upower.service: needs a restart (a library dependency was updated) /usr/bin/systemctl --no-ask-password try-restart upower.service NetworkManager.service: needs a restart (a library dependency was updated) /usr/bin/systemctl --no-ask-password try-restart NetworkManager.service ....
clr-service-restart may cause problems such as a short service outage when a daemon is being restarted, or if a daemon fails to properly restart. To minimize issues, clr-service-restart creates a telemetry record and sends it to the optional Clear Linux OS telemetry service if both conditions below are met:
- If a unit fails to automatically restart after an OS update.
- If that unit resides in the system location
If you do not install the Clear Linux OS telemetrics bundle, the data is discarded. If you install the telemetrics bundle and you opt to send telemetry, then the system unit name is sent to the Clear Linux OS telemetry service. We evaluate the report and update the whitelist to remove services that are not safe to restart.
The Clear Linux OS team enjoys coming up with simple and efficient solutions to make your work easier. We made a GitHub* project of clr-service-restart and we invite you to look at the code, share your thoughts, and work with us on improving the project. You can find the project at: