Support for LUKS disk encryption

[stapelberg]

I just wanted to use embiggen-disk on my NAS, where I use LUKS full-disk encryption.

Unfortunately, embiggen-disk doesn’t seem to support LUKS yet (there’s also an entry in the TODO file), and I get:

root# /tmp/embiggen-disk -verbose -dry-run /srv
error: running lvdisplay -c /dev/mapper/sdb2_crypt: exit status 5; stderr:   /run/lvm/lvmetad.socket: connect failed: No such file or directory
  WARNING: Failed to connect to lvmetad. Falling back to internal scanning.
  Volume group "sdb2_crypt" not found
  Cannot process volume group sdb2_crypt