[Bug 1810351] [NEW] journalctl fails to work inside systemd service

[Edward Gow]

Public bug reported:

Using

Ubuntu 16.04.4 LTS

and

Package: systemd
Architecture: amd64
Version: 229-4ubuntu21.10
Multi-Arch: foreign
Priority: required
Section: admin
Origin: Ubuntu

The journalctl(1) command cannot be used in a systemd OnFailure service
to get error logs. To replicate the issue

1) Create a service unit

[Unit]
Description=%n

[Service]
#ExecStart=/bin/sh -xv -c 'systemctl --user status <your unit> -o cat -n 20 | mail -s "Unit failed" <your email address>'
ExecStart=/bin/sh -c 'journalctl --user-unit=<your unit> -o verbose -q -n 20 | mail -s "Unit failed" <your email address>'

2) enable the unit

3) start the unit

You will get a failure message from journalctl and mail of

sh[28225]: No journal files were opened due to insufficient permissions.
sh[28225]: mail: Null message body; hope that's ok

4) switch the comment # to the journalctl ExecStart and uncomment the
systemctl ExecStart line

>From systemctl you will get journal output in the email.

The man page for systemctl states  "In addition, journalctl --unit=NAME
or journalctl --user-unit=NAME use a similar filter for messages and
might be more convenient."  and indeed it would if it worked properly.

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1810351

Title:
  journalctl fails to work inside systemd service

Status in systemd package in Ubuntu:
  New

Bug description:
  Using

  Ubuntu 16.04.4 LTS

  and

  Package: systemd
  Architecture: amd64
  Version: 229-4ubuntu21.10
  Multi-Arch: foreign
  Priority: required
  Section: admin
  Origin: Ubuntu

  The journalctl(1) command cannot be used in a systemd OnFailure
  service to get error logs. To replicate the issue

  1) Create a service unit

  [Unit]
  Description=%n

  [Service]
  #ExecStart=/bin/sh -xv -c 'systemctl --user status <your unit> -o cat -n 20 | mail -s "Unit failed" <your email address>'
  ExecStart=/bin/sh -c 'journalctl --user-unit=<your unit> -o verbose -q -n 20 | mail -s "Unit failed" <your email address>'

  2) enable the unit

  3) start the unit

  You will get a failure message from journalctl and mail of

  sh[28225]: No journal files were opened due to insufficient permissions.
  sh[28225]: mail: Null message body; hope that's ok

  4) switch the comment # to the journalctl ExecStart and uncomment the
  systemctl ExecStart line

  From systemctl you will get journal output in the email.

  The man page for systemctl states  "In addition, journalctl
  --unit=NAME or journalctl --user-unit=NAME use a similar filter for
  messages and might be more convenient."  and indeed it would if it
  worked properly.

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