Link <code>/etc/mtab</code> to <code>/proc/mounts</code>, for <code>df</code> to work properly:

ln -s /proc/mounts /vz/private/123/etc/mtab  {{out|The problem here is VE's root filesystem (<code>/</code>) is mounted not from the VE itself, but rather from the host system. That leaves <code>/etc/mtab</code> in VE without a record for <code>/</code> being mounted, thus df doesn't show it. By linking <code>/etc/mtab → /proc/mounts</code> we make sure /etc/mtab shows what is really mounted in a VE. Sure this is not the only way to fix df; you can just manually add a line to <code>/etc/mtab</code> telling <code>/</code> is mounted, and make sure this line will be there after a reboot.}}