Add note about trying to mount a uenv with a uenv already mounted

[msimberg]

No description provided.

[github-actions]

preview available: https://docs.tds.cscs.ch/78

[github-actions]

preview available: https://docs.tds.cscs.ch/78

[RMeli]

LGTM and much needed!

The only issue is that searching for "Failed to unshare the mount namespace" or "squashfs-mount: Failed to unshare the mount namespace: Operation not permitted" doesn't seem to hit this warning.

[msimberg]

The only issue is that searching for "Failed to unshare the mount namespace" or "squashfs-mount: Failed to unshare the mount namespace: Operation not permitted" doesn't seem to hit this warning.

Oof, that's very unfortunate. I just checked, and for some reason it seems to show up with a plain unshare search.

Edit: It also seems to show up with "failed to unshare", i.e. when wrapped in quotes. Bad in any case...