What is the difference between "systemctl restart" and "systemctl start"?

Question

I have two services A and B where A is dependent on B which means A needs services provided by B, so in the A's service unit i have After and Requires set to B

After=B.service
Requires=B.service

Now when i stop the service B the service A also stops. And then after stopping B when i start it, the service A is not started and i have to start it manually.

systemctl stop B (A is also stopped)
systemctl start B (A is not started)
systemctl start A (I have to start A manually)

But if the service A is already stopped and i restart service B then the B and A both are started by the systemctl

systemctl stop A
systemctl restart B (B and A both are started)

My question is what is difference between start and restart for the kind of service unit i have for A?

I couldn't find any documentation about the behavior of `systemctl restart` when dependent services are present. Did you? — Ferenc Wágner, Apr 24 '18 at 13:57

score 2 · Answer 1 · answered Mar 27 '15 at 08:05

2

systemctl start: Used to start a service (not reboot persistent)

systemctl stop: Used to stop a service (not reboot persistent)

systemctl restart: Used to stop and then start a service

answered Mar 27 '15 at 08:05

Eric.Chang

71
2

How is it different from `service apache2 reload` ? – sofs1 Aug 11 '19 at 04:42
This was already covered in the quesiton. – Mehdi Charife Jun 18 '23 at 18:43

score 1 · Answer 2 · answered Jun 21 '15 at 14:46

You can always refer man pages for better understanding. Basically wants,requires,after are treated differently.

Dependencies react differently to wants and requires in a service file.

Start is simply starting a service when you want to use it but restart is mostly done when some changes are made in service files. Refer this link for better understanding https://wiki.archlinux.org/index.php/Systemd.

What is the difference between "systemctl restart" and "systemctl start"?

2 Answers2