Convenient way to check if system is using systemd or sysvinit in BASH?

Question

I am defining common bash files which I want to use across different distributions. I need a way to check if system is using systemd or sysvinit (/etc/init.d/). I need this so I run appropriate command to start the service. What would be safe way to check for this? I currently check for existance of systemctl command, but is that really an option as there might be the case where systemctl command might be available, but it wouldn't necessarily mean that systemd is actually used?

Here is an excerpt from my current bash script:

#!/bin/sh
if [ command -v systemctl >/dev/null ]
then
    systemctl service start
else
    /etc/init.d/service start
fi

Solution

Systemd and init have pid = 1

pidof /sbin/init && echo "sysvinit" || echo "other"

Check for systemd

pidof systemd && echo "systemd" || echo "other"

Comments

[Admin]

That question was more related when creating an installer package and the general consensus on the answer was to implement it in a different way. I feel that my question provides a different case, which could provide a different solution/answer to this. I will keep it open for some time and delete it if it does not get any attention.

[Admin]

Unfortunately, there is no clean, surefire way of doing this. You should also have a look through this Q&A for some possible workarounds.

[Admin]

When will that not echo sysvinit? AFAIK, all (or most) init systems will have a PID of 1, that's kind of part of the definition.

[Admin]

well, than the other way will be correct?

[Admin]

No, for example Ubuntu with upstart still reports /sbin/init. Have a look at @slm's answer in the linked dupe for more details.

[Admin]

I meant if checking for systmed as showed last is ok?

[Admin]

Ah, yes, that's better, downvote retracted.

[Admin]

Commenting to say that the check for systemd works on Ubuntu 14.04, 15.04 and 15.10, but not on debian jessie 8.2.

[Admin]

On my old Debian I get both "sysvinit" and "systemd"

[Admin]

First solution is wrong because /sbin/init is probably symbolic link to /lib/systemd/systemd. To check it run file /sbin/init.

[Admin]

+1 for pstree -p, -1 for the rest of this answer.

[Admin]

-1 for the misleading pidof init as it may be a symbolic link to systemd. +1 for the comments here that have more than sufficient answers to help who comes here. Try for example: [[ -L "/sbin/init" ]] && echo 'systemd' || echo 'systemV'

[Admin]

Actually this doesn't work with Ubuntu. with pidof systemd doesn't show the correct systemd id. Rather, it would be useful if you use the following instead: cat /proc/1/status|egrep -i 'name|state' because systemd replaces sysvinit with the id == 1 in the system process. Hope this helps

[Admin]

The right way to determine whether systemd is managing the system is to check for the existence of /run/systemd/system.