[SOLVED] ERROR on backup restore of a LXC container: "Cannot change ownership to uid 65534, gid 65534: Invalid argument"

[jrhbcn]

Hi,

I am trying to restore a backup of an LXC container from one pve host to another one (different clusters, I am just copying the dump backup to the new host and restore). The LXC container is unpriviledge with keyctl and nesting on. Also there is a mount bind and user mapping on the config like this:

arch: amd64
cores: 2
features: keyctl=1,nesting=1
hostname: media
memory: 512
mp0: /mnt/pve/data,mp=/data
net0: name=eth0,bridge=vmbr0,firewall=1,gw=192.168.1.1,hwaddr=42:27:23:1E:E5:E0,ip=192.168.1.17/24,type=veth
ostype: debian
rootfs: local-lvm:vm-117-disk-0,size=3G
swap: 0
unprivileged: 1
lxc.idmap: u 0 100000 1000
lxc.idmap: u 1000 1000 1
lxc.idmap: u 1001 101001 64530
lxc.idmap: g 0 100000 1000
lxc.idmap: g 1000 1000 1
lxc.idmap: g 1001 101001 64530
lxc.idmap: g 65534 165534 1

I have moved the backup to the new pve server, both old server (where backup comes from) and new server have /etc/subuid and /etc/subgid like:

root:1000:1
root:100000:65536
media:165536:65536

When I try to restore the backup I gest the following error:

recovering backed-up configuration from 'local:backup/vzdump-lxc-117-2023_03_19-08_47_17.tar.zst'
restoring 'local:backup/vzdump-lxc-117-2023_03_19-08_47_17.tar.zst' now..
extracting archive '/var/lib/vz/dump/vzdump-lxc-117-2023_03_19-08_47_17.tar.zst'
tar: ./etc/vzdump/pct.conf: Cannot change ownership to uid 65534, gid 65534: Invalid argument
tar: ./etc/vzdump/pct.fw: Cannot change ownership to uid 65534, gid 65534: Invalid argument
Total bytes read: 1189570560 (1.2GiB, 291MiB/s)
tar: Exiting with failure status due to previous errors
TASK ERROR: unable to restore CT 117 - command 'lxc-usernsexec -m u:0:100000:1000 -m u:1000:1000:1 -m u:1001:101001:64530 -m g:0:100000:1000 -m g:1000:1000:1 -m g:1001:101001:64530 -m g:65534:165534:1 -- tar xpf - --zstd --totals --one-file-system -p --sparse --numeric-owner --acls --xattrs '--xattrs-include=user.*' '--xattrs-include=security.capability' '--warning=no-file-ignored' '--warning=no-xattr-write' -C /var/lib/lxc/117/rootfs --skip-old-files --anchored --exclude './dev/*'' failed: exit code 2

Any ideas what I can do for it to work? Thanks,

 

[fweber]

Hi, I think the problem is that the custom id mapping is missing a mapping for container uid 65534. This is the nobody user, who is also the owner of /etc/vzdump/pct.conf and /etc/vzdump/pct.fw in the backup archive.

This line:

lxc.idmap: u 1001 101001 64530

only maps container uids from 1001 to 65530. You could try extending this line to also include 65534, e.g.

 lxc.idmap: u 1001 101001 64535

 

[jrhbcn]

@fweber that is indeed the problem, as soon as I added the line, backup & restore was working. Many thanks for the help.

 

[david-moreira]

Hello,
@fweber , @jrhbcn
I have this same problem, how do you edit the backup lxc configuration file to make this change?

Thanks!!