Systemd – Reloading a Single Unit/Service File After Modification

systemd

Can I reload a single systemd unit/service file after its modification (in [Service] section) without reloading all unit files? By online search, everyone talk about systemctl daemon-reload or systemctl --user daemon-reload. This makes me feel really bad. I only want to reload one unit file configuration instead of many. Is that possible to reload the modified one only in systemd? Thanks a lot.

Best Answer

systemctl daemon-reload cannot be run on a single unit file. What it does is reloading the systemd configurations of unit files, rerun all generators and recreates the dependency tree.

I guess since the dependency tree is regenerated it doesn't make sense to run this on a single unit as several unit files may have changed and the dependency tree then could be wrong.

Related Solutions

Find the location of a systemd unit file service

For units that are defined in actual, static files, this can be seen in systemctl status:

$ systemctl status halt-local.service
● halt-local.service - /usr/sbin/halt.local Compatibility
   Loaded: loaded (/lib/systemd/system/halt-local.service; static)
   Active: inactive (dead)

But there are units that are not defined by files, e.g. with systemd-cron installed. These have no useful location listed with status:

$ systemctl status cron-jojo-0.timer
● cron-jojo-0.timer - [Cron] "*/10 * * * * ..."
   Loaded: loaded (/var/spool/cron/crontabs/jojo)
   Active: active (waiting) since Mon 2015-05-18 14:53:01 UTC; 9min ago

In either case, though, the FragmentPath field is educating:

$ systemctl show -p FragmentPath cron-daily.service
FragmentPath=/lib/systemd/system/cron-daily.service
$ systemctl show -p FragmentPath cron-jojo-0.service
FragmentPath=/run/systemd/generator/cron-jojo-0.service
$ systemctl show -p FragmentPath halt-local.service
FragmentPath=/lib/systemd/system/halt-local.service

Systemd – How to Restart All Instances of an Instantiated Service at Once

Systemd (starting from systemd-209) supports wildcards, however your shell is likely trying to expand them. Use quotes to pass wildcards to the systemctl/service command verbatim:

systemctl restart 'autossh@*'

Best Answer

Related Solutions

Find the location of a systemd unit file service

Systemd – How to Restart All Instances of an Instantiated Service at Once

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