[Bug 1865037] Re: make the service fail gracefully if unable to load modules

[Billy Olsen]

This bug is also a problem on focal. When trying to install in a
container, the service fails to start with:


invoke-rc.d: initscript rtslib-fb-targetctl, action "start" failed.
● rtslib-fb-targetctl.service - Restore LIO kernel target configuration
     Loaded: loaded (/lib/systemd/system/rtslib-fb-targetctl.service; disabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Thu 2021-06-24 18:08:27 UTC; 13ms ago
    Process: 1232 ExecStart=/usr/bin/mkdir -p /etc/rtslib-fb-target (code=exited, status=0/SUCCESS)
    Process: 1233 ExecStart=/usr/bin/targetctl restore (code=exited, status=1/FAILURE)
   Main PID: 1233 (code=exited, status=1/FAILURE)

Jun 24 18:08:27 closing-anemone target[1233]:   File "/usr/bin/targetctl", line 47, in restore
Jun 24 18:08:27 closing-anemone target[1233]:     errors = RTSRoot().restore_from_file(restore_file=from_file)
Jun 24 18:08:27 closing-anemone target[1233]:   File "/usr/lib/python3/dist-packages/rtslib_fb/root.py", line 85, in __init__
Jun 24 18:08:27 closing-anemone target[1233]:     modprobe('target_core_mod')
Jun 24 18:08:27 closing-anemone target[1233]:   File "/usr/lib/python3/dist-packages/rtslib_fb/utils.py", line 428, in modprobe
Jun 24 18:08:27 closing-anemone target[1233]:     raise RTSLibError(stderrdata)
Jun 24 18:08:27 closing-anemone target[1233]: rtslib_fb.utils.RTSLibError: b'modprobe: FATAL: Module target_core_mod not found in directory /lib/modules/5.8.0-55-generic\n'
Jun 24 18:08:27 closing-anemone systemd[1]: rtslib-fb-targetctl.service: Main process exited, code=exited, status=1/FAILURE
Jun 24 18:08:27 closing-anemone systemd[1]: rtslib-fb-targetctl.service: Failed with result 'exit-code'.
Jun 24 18:08:27 closing-anemone systemd[1]: Failed to start Restore LIO kernel target configuration.
dpkg: error processing package python3-rtslib-fb (--configure):
 installed python3-rtslib-fb package post-installation script subprocess returned error exit status 1
Processing triggers for systemd (2dmesg: read kernel buffer failed: Operation not permitted

I can confirm that the ConditionVirtualization=!container directive
added to the service file addresses the issue.


** Also affects: cloud-archive
   Importance: Undecided
       Status: New

** Also affects: cloud-archive/ussuri
   Importance: Undecided
       Status: New

** Changed in: cloud-archive
       Status: New => Triaged

** Changed in: cloud-archive
   Importance: Undecided => High

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https://bugs.launchpad.net/bugs/1865037

Title:
  make the service fail gracefully if unable to load modules

Status in Ubuntu Cloud Archive:
  Triaged
Status in Ubuntu Cloud Archive ussuri series:
  New
Status in rtslib-fb:
  Unknown
Status in python-rtslib-fb package in Ubuntu:
  Fix Released
Status in python-rtslib-fb source package in Focal:
  Confirmed
Status in python-rtslib-fb source package in Groovy:
  Fix Released

Bug description:
  [Impact]
  ========

  The LIO interfaces is inherently tied to the kernel.
  That makes the service fail on e.g. a container install:

  See "systemctl status rtslib-fb-targetctl.service" and "journalctl -xe" for details.
  root at f:~# systemctl status rtslib-fb-targetctl.service
  ● rtslib-fb-targetctl.service - Restore LIO kernel target configuration
       Loaded: loaded (/lib/systemd/system/rtslib-fb-targetctl.service; disabled; vendor preset: enabled)
       Active: failed (Result: exit-code) since Thu 2020-02-27 14:10:35 UTC; 3s ago
      Process: 23831 ExecStart=/usr/bin/mkdir -p /etc/rtslib-fb-target (code=exited, status=0/SUCCESS)
      Process: 23832 ExecStart=/usr/bin/targetctl restore (code=exited, status=1/FAILURE)
     Main PID: 23832 (code=exited, status=1/FAILURE)

  Feb 27 14:10:35 f target[23832]:   File "/usr/bin/targetctl", line 47, in restore
  Feb 27 14:10:35 f target[23832]:     errors = RTSRoot().restore_from_file(restore_file=from_file)
  Feb 27 14:10:35 f target[23832]:   File "/usr/lib/python3/dist-packages/rtslib_fb/root.py", line 85, in __init__
  Feb 27 14:10:35 f target[23832]:     modprobe('target_core_mod')
  Feb 27 14:10:35 f target[23832]:   File "/usr/lib/python3/dist-packages/rtslib_fb/utils.py", line 428, in modprobe
  Feb 27 14:10:35 f target[23832]:     raise RTSLibError(stderrdata)
  Feb 27 14:10:35 f target[23832]: rtslib_fb.utils.RTSLibError: b"modprobe: ERROR: ../libkmod/libkmod.c:611 kmod_search_moddep() could not open moddep file '/lib/modules/5.3.0-40-generic/modu>
  Feb 27 14:10:35 f systemd[1]: rtslib-fb-targetctl.service: Main process exited, code=exited, status=1/FAILURE
  Feb 27 14:10:35 f systemd[1]: rtslib-fb-targetctl.service: Failed with result 'exit-code'.
  Feb 27 14:10:35 f systemd[1]: Failed to start Restore LIO kernel target configuration.

  It is ok that this doesn't work in a container, but it also breaks the
  package installation status which should be avoided.

  
  [Test Plan]
  ===========

  To reproduce this bug, simply do the following:

  $ lxc launch ubuntu-daily:groovy python-rtslib-fb-lp1865037-groovy

  $ lxc shell python-rtslib-fb-lp1865037-groovy

  # apt update && apt upgrade

  # reboot

  # apt install python3-rtslib-fb

  ...and this should fail to install.

  To make sure that this bug is indeed fixed, install the patched
  version of this package and that should install fine.

  
  [Where problems could occur]
  ============================

  
  This is a workaround since there doesn't seem to be a in-container use case. But in case there is one, then that'd fail to work, so we might better find a better solution for this in the long term.

  The disccusion has been initiated upstream (cf: https://github.com
  /open-iscsi/rtslib-fb/issues/157) and probably we'll wait for upstream
  to state some in-container use case(s).

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