如何配置系统服务以定期重新启动？

我有一个简单的系统服务，需要定期重新启动，以防止它的进程崩溃。系统服务是否有定期重新启动它们的配置选项？所有的 Restart*选项似乎都与服务退出时重新启动有关。

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Just some alternate approaches to ultimately reach the same goal:

  • if you have control over the service implementation you could make it end voluntarily after a while, for example either plain exiting after a certain number of iterations (if applicable) or using a timeout timer with a handler sendin itself a SIGTERM/SIGKILL
  • if voluntary service ending is not feasible/practical you could have a small cron-based script killing the service process(es).
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最佳答案

Yes, you can make your service to restart it periodically by making your service of Type=notify. Add this option in [Service] section of your service file along with Restart=always and give WatchdogSec=xx, where xx is the time period in second you want to restart your service. Here your process will be killed by systemd after xx time period and will be restarted by systemd again. for eg.

[Unit]
.
.


[Service]
Type=notify
.
.
WatchdogSec=10
Restart=always
.
.


[Install]
WantedBy= ....
小开

I saw a solution here that seemed elegant, if a bit roundabout. The key idea is to create a one-shot service triggered by a timer that restarts another service.

For the timer: 

[Unit]
Description=Do something daily


[Timer]
OnCalendar=daily
Persistent=true


[Install]
WantedBy=timers.target

For the one-shot service: 

[Unit]
Description=Restart service


[Service]
Type=oneshot
ExecStart=/usr/bin/systemctl try-restart my_program.service

For the one-shot service on Ubuntu 16.04 LTS: 

[Unit]
Description=Restart service


[Service]
Type=oneshot
ExecStart=/bin/systemctl try-restart my_program.service

This solution lets you leverage systemd's timers, including the ability to restart the service at a particular time of day, and not just after some amount of time has elapsed.

小开

How about a crontab. Example:

30 3 * * sun /bin/systemctl restart yourService

That would restart the service named yourService at 3:30 AM each Sunday.

You may like this solution if you want something working in whatever Unix-like server (e.g. you do not want to worry about a specific systemd version, etc.).

小开

For systemd version >= 229, there is an option called RuntimeMaxSec, which terminates the service after it has been running for the given period of time.

e.g. To restart every 7 days:

[Service]
Restart=always
RuntimeMaxSec=7d

To me this seems more elegant than abusing Type=notify and WatchdogSec.

systemd provides a clean way to add and override directives in systemd unit files provided by vendors. Drop-In Units are described in man systemd.unit. For example, if you wanted to periodically restart the foo service provided by a package, you would create a file named /etc/systemd/system/foo.service.d/periodic-restart.conf. The contents would be as shown above. Then:

 systemctl daemon-reload
systemctl restart foo

You can confirm that the Drop-In unit has been loaded because it will be reported in the status output:

 systemctl status

Finally, you can confirm the directive has been included by searching the systemctl show output:

 systemctl show foo.service | grep RuntimeMax

The directive reported by systemctl show will be "RuntimeMaxUSec`

小开

Wanted to comment on the 

[Service]
Restart=always
RuntimeMaxSec=604800

answer above but can't w/o more points.

Comment is that this solution will invoke failure handling set by OnFailure=failure_handling.service. Since the scheduled restart isn't a real failure any logging, notifications, etc. from the failure handling service will be unwanted and probably disruptive.

An actual periodic restart would be a sensible feature for systemd, but I won't hold my breath.

小开

Copy-paste solution for systemd version >= 229:

SERVICE="systemd-resolved.service"
env SYSTEMD_EDITOR=tee sudo -E systemctl edit --system ${SERVICE} <<EOF
[Service]
Restart=always
RuntimeMaxSec=7200
EOF


sudo systemctl daemon-reload && sudo systemctl restart "${SERVICE}"

Check:

systemd-delta | grep ${SERVICE}
# NOTE: property here must be requested with "U": RuntimeMaxUSec
systemctl show ${SERVICE} --property=RuntimeMaxUSec

Rollback:

SERVICE="systemd-resolved.service"
sudo rm -r "/etc/systemd/system/${SERVICE}.d"
sudo systemctl daemon-reload
sudo systemctl restart ${SERVICE}

More elegant would be the following:

SERVICE="systemd-resolved.service"
sudo systemctl set-property ${SERVICE} RuntimeMaxSec=7200

But it does not work for some reason:

Failed to set unit properties on systemd-resolved.service: Cannot set property RuntimeMaxUSec, or unknown property.

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