FYI: When converting containers via lxd-p2c, old (no longer present/relevant) entries in /etc/fstab can cause IP Address to not be set

(Adam Chalkley) #1

Not sure whether this is a known issue (perhaps something I should have just “known” as a Linux server admin), but figured I’d share in case someone else runs into the same issue.

I copied a live system (VMware VM in this case) via lxd-p2c like so:

$ sudo ./lxd-p2c wordpress-test / /boot

and ended up with a container which has the contents of ‘/’ and ‘/boot’. That part worked.

However, the /etc/fstab file in the newly generated container still has the mount points from the old system. At boot time, the entry within the /etc/fstab time in the container were enough to cause the network configuration to not be applied as expected. Once I commented out the entries within the /etc/fstab file and restarted the container, the system was able to pull an IP Address via DHCP as intended.

On a related note:

After very brief testing, I was able to have the container start without issue without a /etc/fstab file present. Is that file even needed within a LXD container? I assume it is, but very quick testing appears to indicate otherwise. Would an empty /etc/fstab file cause any issues?

(Stéphane Graber) #2

lxd-p2c doesn’t perform any modification to the container’s content as such modifications would be very distribution and environment specific.

It’s indeed up to the user to perform the few post-migration steps that may be required.
In some cases it’s updating network configuration files, in some other, cleaning up no longer relevant /etc/fstab entries, sometimes it involves disabling some services, …

Your distribution in the container still does use /etc/fstab, though LXD does pre-mount /, /proc and /sys, so if that’s all you have in there, it’s indeed not actually used.

(Adam Chalkley) #3

Understood. Thanks for explicitly noting those details. On a related note, is there a separate docs page for lxd-p2c? This seems like great material to include in such a page.

Ah, OK that makes sense. Is that configurable from a property somewhere in a profile or on the container itself? Just curious.

Thank you for your time!

(Stéphane Graber) #4

Not really, you can manually mess with raw.lxc and modifying the config option through that, but it’s not something we’d recommend.

(Adam Chalkley) #5

Thanks for confirming, I appreciate your quick and detailed responses.