Intro:

Even tho CMK itself advises against it, under some conditions this still is a viable option.
So to show how, i’ve written this small tutorial.

Assumptions:

    a running LXC-Container with a supported OS for CheckMK on Proxmox.
    basic setup of CheckMK (any edition) - with atleast one site configured.

Issues (without further configuration)

    Temporary filesystem will give a warning - indicating performance is not optimal when doing a (re-)start.

Creating temporary filesystem /omd/sites/testsite/tmp...mount: /opt/omd/sites/testsite/tmp: can't find in /etc/fstab.
WARNING: You may continue without tmpfs, but the performance of Check_MK may be degraded.

Solution:

For every configured site on the box edit (even if it does not exist) with your favorite editor /etc/fstab and enter the following information (per-site):

[code]
tmpfs   /opt/omd/sites/<yoursitename>/tmp     tmpfs   noauto,user,mode=755,uid=<yoursitename>,gid=<yoursitename>2 0 0
[/code]
After having made these adjustment you will have to restart the box.

Result:

    you now have a temporary filesystem in place for a/the sites you are running without OMD complaining about missing tmpfs.

Happy monitoring !