lxd init fails with 'Address already in use'

[Heinrich Schuchardt]

Snapcraft failed due to missing lxdbr0. So I uninstalled the lxd snap rebooted and reinstalled the lxd snap.

lxd init fails to create lxdbr0:

$ lxd init
Would you like to use LXD clustering? (yes/no) [default=no]:
Do you want to configure a new storage pool? (yes/no) [default=yes]:
Name of the new storage pool [default=default]:
Name of the storage backend to use (btrfs, ceph, cephobject, dir, lvm, zfs) [default=zfs]:
Create a new ZFS pool? (yes/no) [default=yes]:
Would you like to use an existing empty block device (e.g. a disk or partition)? (yes/no) [default=no]:
Size in GiB of the new loop device (1GiB minimum) [default=30GiB]:
Would you like to connect to a MAAS server? (yes/no) [default=no]:
Would you like to create a new local network bridge? (yes/no) [default=yes]:
What should the new bridge be called? [default=lxdbr0]:
What IPv4 address should be used? (CIDR subnet notation, “auto” or “none”) [default=auto]:
What IPv6 address should be used? (CIDR subnet notation, “auto” or “none”) [default=auto]:
Would you like the LXD server to be available over the network? (yes/no) [default=no]:
Would you like stale cached images to be updated automatically? (yes/no) [default=yes]:
Would you like a YAML "lxd init" preseed to be printed? (yes/no) [default=no]:
Error: Failed to create local member network "lxdbr0" in project "default": The DNS and DHCP service exited prematurely: Process exited with non-zero value 2 ("dnsmasq: failed to create listening socket for 10.37.129.1: Address already in use")

$ lxc network show lxdbr0
If this is your first time running LXD on this machine, you should also run: lxd init
To start your first container, try: lxc launch ubuntu:22.04
Or for a virtual machine: lxc launch ubuntu:22.04 --vm

Error: Network not found

After I uninstalled the maas snap lxd init worked find.

Can we have a less cryptic message describing why lxdbr0 cannot be created?

Telling the user that an application that binds to all interfaces on port 53 is incompatible with LXD would be helpful.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Steven Parker (sbparke)]

You can also just:
sudo snap stop maas

Then init lxd

No need to remove the maas snap.

[Simon Déziel (sdeziel)]

If I'm reading the issue properly, that 10.37.129.1 address would be from the newly created `lxdbr0` bridge where LXD wants to setup a dnsmasq listener.

Now presumably that fails because something in MAAS (bind9?) raced with it and started a listener on it before dnsmasq got a chance.

IIRC, bind9 has a feature that spawns listeners on newly created interfaces, so maybe MAAS could turn that feature off to play more nicely with other listeners?

[Simon Déziel (sdeziel)]

https://bind9.readthedocs.io/en/v9.18.27/reference.html#namedconf-statement-automatic-interface-scan is the default enabled feature that causes bind9 to start the conflicting listener, or at least I think it is.

I believe this is more a bug with how MAAS configures bind9 than something LXD could improve on. LXD really needs that dnsmasq listener so bind9 taking it over is nothing LXD can do about.