Update instructions for starting container on reboot

[Mygod]

Related: https://stackoverflow.com/a/57532307/2245107

[CLAassistant]

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[huan]

Thanks for your contribution! But I believe the --restart=always docker run parameter has already made the container start on reboot?

[Mygod]

According to my test it only starts after logon.

[huan]

I don't think do, because I have many servers and I don't remember there's any cases that the container can not get started after the server reboot.

Could you please double confirm it?

[Mygod]

Actually it only runs after I run docker ps. Selection of syslog:

May  3 09:22:55 server kernel: [    0.000000] Linux version 5.3.0-51-generic (buildd@lgw01-amd64-018) (gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04))
#44~18.04.2-Ubuntu SMP Thu Apr 23 14:27:18 UTC 2020 (Ubuntu 5.3.0-51.44~18.04.2-generic 5.3.18)
...
(log in)
May  3 09:27:45 server systemd[1]: Starting User Manager for UID 0...
...
(run docker ps)
May  3 09:30:08 server systemd[1]: Reached target Network is Online.
May  3 09:30:08 server systemd[1]: Starting Docker Application Container Engine...

Using crontab fixes this.

[huan]

I'll have a test about it when I got time.

Basically I don't think that there's any need to add anything into the crontab.

[huan]

I believe the answer in the StackOverflow link agree with me that there's no crontab need to be added: https://stackoverflow.com/a/30450350/1123955