I’ve got a Proxmox VE host running with a couple of LXC containers which used to run on Ubuntu 16.04. After I upgraded them to 18.04 I received a daily e-mail from every LXC container with the following error:
/etc/cron.daily/logrotate: Failed to kill unit rsyslog.service: Input/output error error: error running non-shared postrotate script for /var/log/syslog of '/var/log/syslog' run-parts: /etc/cron.daily/logrotate exited with return code 1
I tried to fix it a couple times but never managed to find the real issue. Today I found the solution thanks to a German thread on the Proxmox forums.
The real error message which causes logrotate to fail can be found by executing:
logrotate -v /etc/logrotate.d/rsyslog
error: skipping "/var/log/syslog" because parent directory has insecure permissions (It's world writable or writable by group which is not "root") Set "su" directive in config file to tell logrotate which user/group should be used for rotation.
According to our German friends there is a new version of rsyslog which fixes the issue. It can be installed with the following commands:
apt install software-properties-common add-apt-repository ppa:adiscon/v8-stable apt install -y rsyslog
For safety I reboot the LXC container to make sure the new version of the service is running.
There is a final note about a message appearing in /var/log/syslog every few seconds but I haven’t seen that happen.