#1009963 deb-systemd-helper: Misleading error message in "sub enable" if systemctl fails

Package:
init-system-helpers
Source:
init-system-helpers
Submitter:
Sascha Herrmann
Date:
2022-04-22 09:39:08 UTC
Severity:
normal
#1009963#5
Date:
2022-04-21 10:33:19 UTC
From:
To:
Dear Maintainer,

the code line 'or error("systemctl preset failed on $scriptname: $!");' prints
some misleading information, if the systemctl command fails and returns an
return value != 0. When using the systemctl package (systemctl-replacement),
some packages fail to setup their service files, systemctl returns the error
code 1 which results in a message like

"/usr/bin/deb-systemd-helper: error: systemctl preset failed on keyboard-setup.service: No such file or directory"

The "No such file or directory" is produced by the $! part of the error string,
but $! isn't actually set by the system() call. The wrong (and random) error
messages gives wrong hints, when searching for the root cause of the problem
triggering the failure to install the service file. $! should only be used if
the system() call returned -1.

Thanks,
Sascha
#1009963#10
Date:
2022-04-21 16:13:12 UTC
From:
To:
Am 21.04.22 um 12:33 schrieb Sascha Herrmann:

So /usr/bin/systemctl is provided by the "systemctl" package?
Can you post the output of
apt-cache policy systemctl

Please uninstall the systemctl package and test if the failure is gone.

Regards,
Michael
#1009963#15
Date:
2022-04-21 16:37:20 UTC
From:
To:
Hi,

I think the bug reporter suggest to replace the

  system(...) == 0 or error("systemctl preset failed on $scriptname: $!");

with a more correct (and verbose)

  system(...);
  if ($? == -1) {
    error("systemctl preset failed on $scriptname: $!");
  }
  elsif ($? & 127) {
    error("systemctl preset died with signal " . ($? & 127));
  }
  else {
    error("systemctl preset failed with return status " . ($? >> 8));
  }

as `perldoc -f system` suggest. (Untested, so might contain typos and
the like.)

Currently it always give "$!" as the reason, even when not correct.
This would also be incorrect if the real systemctl is used if the
command fails because of syntax errors or so.

Ansgar
#1009963#20
Date:
2022-04-21 17:08:26 UTC
From:
To:
Am 21.04.22 um 18:37 schrieb Ansgar:

I guess we have two issues then:
- systemctl (from docker-systemctl-replacement) most likely not being
compatible with the real systemctl
- handling of the return code from system()

We do have quite a few calls to system() in our perl code.
#1009963#25
Date:
2022-04-22 09:31:52 UTC
From:
To:
Yes, i think this is correct. I will fill an additional bug report for
the systemctl package, which is the root cause of the problem. The bug
reported here just gave some additional headaches while searching the
real problem.

Thanks,
Sascha