systemctl location

[rjschwei]

Proposed Commit Message

It is reasonable to expect that "systemctl" is found in one of the locations in the PATH

• Using the '/bin' prefix is very distribution specific. A number of
  distributions are moving all executables from '/' to '/usr'.

systemctl may bot be in `/bin`

Additional Context

Test Steps

cloud-init on a distribution where systmctl is in /usr/bin produces an error
Command: ['/bin/systemctl', 'show', '-p', 'UserspaceTimestampMonotonic']
[ 37.366919] cloud-init[882]: Exit code: -
[ 37.369468] cloud-init[882]: Reason: [Errno 2] No such file or directory:

Checklist:

• [ x] My code follows the process laid out in the documentation
• [x ] I have updated or added any unit tests accordingly
• I have updated or added any documentation accordingly

[Conan-Kudo]

Is anyone actually doing this in a way where /bin isn't a symlink to /usr/bin? Fedora, openSUSE, and Ubuntu all have a persistent symlink for this...

[rjschwei]

Is anyone actually doing this in a way where /bin isn't a symlink to /usr/bin? Fedora, openSUSE, and Ubuntu all have a persistent symlink for this...

See the error message posted, I really don't make this stuff up.

In any event it is reasonable to assume that systemctl will be on the path and if we don't want to make that assumption then we should be using subp.which() everywhere rather than assuming the executable lives in /bin or there exists a symlink

[smoser]

I agree with the intent. hard coded paths are nonsense.

[TheRealFalcon]

Thanks!