Backup or move an LXC container

You can not just copy an LXC container, wat you need to do is among the lines of

cd /var/lib/lxc
tar --numeric-owner -cf container_125_fs.tar vm125

The magic is mainly about maintaining the numeric owner of files, which is lost when you copy the files using the host machine 😉

you can untar it the same way you untar any other tar file.