[Solved] CheckMK sets wrong permissions on fstab, breaks Snap packages

CMK version: check-mk-raw-2.4.0p17
OS version: Ubuntu 24.04

I installed CheckMK on Ubuntu 24.04, and followed the instructions at https://docs.checkmk.com/latest/en/intro_setup.html

Basically:
omd create --admin-password somepassword domain_com # create a site for my stuff
sudo su - domain_com
omd start # start the site
omd status

I then found that desktop apps installed via Snap, in particular Firefox which is by default from Snap on Ubuntu, failed with:

$ firefox

2025/12/29 05:52:38.725126 system_key.go:147: cannot determine nfs usage in generateSystemKey: cannot parse /etc/fstab: open /etc/fstab: permission denied
interner Fehler, bitte melden: Ausführung von “firefox” fehlgeschlagen: timeout waiting for snap system profiles to get updated

The reason was that the omd command had altered the permissions on /etc/fstab:

$ ls -l /etc/fstab
-rw-r----- 1 root root 1405 Dez 29 05:53 /etc/fstab

I could workaround the bug by restoring the OOB Ubuntu permissions for it:
sudo chmod 644 /etc/fstab

The omd command should never alter permissions on the /etc/fstab file. I’ve reported this as a bug via the feedback email, but thought I’d post here for visibility.

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