Start service on system boot with systemd

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systemd

systemd counld be used for running program on system boot/reboot.

常用的格式和字段：

Unit

  • Description
  • Before
  • After

Service

  • EnvironmentFile
  • ExecStart
  • ExecStop
  • ExecReload
  • ExecStartPre
  • ExecStartPos
  • ExecStopPost
  • Type
  • Restart

Install

  • WantsBy

Examples

Create redis.service

Here we will write a redis.service to start redis-server on system boot:

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[Unit]
Description=Redis
After=network.target

[Service]
User=redis
Group=redis
ExecStart=/usr/local/bin/redis-server /home/redis/6379.conf
ExecStop=kill -s HUP $MAINPID
Restart=on-failure

[Install]
WantedBy=multi-user.target

Then:

1, Copy this file to path /lib/systemd/system/

2, Start service with systemctl start redis. Make sure your redis config file set the daemonize to no, if you set to yes, in the later run systemctl start step, it will fail. Now your redis-server should be running, you could check its running status with systemctl status redis.

3, To stop it, run systemctl stop redis

If you changed the service file content, you need to reload it:

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systemctl daemon-reload

To make it run on system boot, you need:

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systemctl enable redis

This will create a symbol link to your file under /etc/systemd/system/multi-user.target.wants/ folder, and after your system reboot, it will auto start this redis service.

Other examples

In this /etc/systemd/system/multi-user.target.wants folder, there are some other service files we can learn as example:

ufw.service

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[Unit]
Description=Uncomplicated firewall
Documentation=man:ufw(8)
DefaultDependencies=no
Before=network.target

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/lib/ufw/ufw-init start quiet
ExecStop=/lib/ufw/ufw-init stop

[Install]
WantedBy=multi-user.target

cron.service

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[Unit]
Description=Regular background program processing daemon
Documentation=man:cron(8)
After=remote-fs.target nss-user-lookup.target

[Service]
EnvironmentFile=-/etc/default/cron
ExecStart=/usr/sbin/cron -f $EXTRA_OPTS
IgnoreSIGPIPE=false
KillMode=process
Restart=on-failure

[Install]
WantedBy=multi-user.target

supervisor.service

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[Unit]
Description=Supervisor process control system for UNIX
Documentation=http://supervisord.org
After=network.target

[Service]
ExecStart=/usr/bin/supervisord -n -c /etc/supervisor/supervisord.conf
ExecStop=/usr/bin/supervisorctl $OPTIONS shutdown
ExecReload=/usr/bin/supervisorctl -c /etc/supervisor/supervisord.conf $OPTIONS reload
KillMode=process
Restart=on-failure
RestartSec=50s

[Install]
WantedBy=multi-user.target

Compare to supervisor

supervisor is a good tool to run program too. So I think if the service is the basic infra applications, like redis, mysql, mongodb, you could set it under systemd, b/c supervisor doesn’t have a good “dependency” running order supported. Then in the application layer, you could just use supervisor which have more flexible settings for applications.

Reference