systemd/extras/volume_id/README

vol_id - probe filesystem and read label and uuid

This program is normally called from a udev rule, to provide udev with the
filesystem type of a volume and the label and uuid to name a device node.
vol_id opens the blockdevice node specified at the commandline. The following
commandline switches are supported to specify what vol_id should print:

  --export prints all values
  -h       prints help text
  -l       prints the label of the volume
  -u       prints the uuid of the volume

vol_id will only return successful if the string asked for, is not
empty. All trailing whitespace will be removed, spaces replaced by underscore
and slashes ignored.

fstype                 probe  label  uuid  fsversion
----------------------------------------------------
linux swap             *      *      *     *
ext                    *      *      *     *
reiserfs jr/3.5/3.6/4  *      *      *     *
fat (12, 16, 32)       *      *      *     *
ntfs                   *      *      *     *
jfs                    *      *      *     -
xfs                    *      *      *     -
hfs (plus, wrapped)    *      *      *     -
udf                    *      *      -     -
iso9660                *      *      -     -
ufs                    *      -      -     -
cramfs                 *      *      -     -
sysv                   *      *      -     *
luks                   *      -      *     -
hpfs                   *      -      -     -
romfs                  *      *      -     -
squashfs               *      -      -     -
minix                  *      -      -     *
ocfs (1, 2)            *      *      *     *
vxfs                   *      -      -     *

Raid members are detected to prevent the probing for a filesystem
-----------------------------------------------------------------
linux raid             *      -      *     *
LVM 1                  *      -      -     -
LVM 2                  *      -      -     *
highpoint              *      -      -     -
isw_raid               *      -      -     -
lsi_raid               *      -      -     -
nvidia_raid            *      -      -     -
promise_raid           *      -      -     -
silicon_raid           *      -      -     -
via_raid               *      -      -     -


If no label is found vol_id exits with nonzero and the rule will be
ignored.

To give it a try, you may call it on the commandline:
  $ extras/volume_id/vol_id --export /dev/sda6
  ID_FS_USAGE=filesystem
  ID_FS_TYPE=ext3
  ID_FS_VERSION=1.0
  ID_FS_UUID=3e999973-00c9-4917-9442-b7633bd95b9e
  ID_FS_LABEL=devel
  ID_FS_LABEL_SAFE=devel

  $ extras/volume_id/vol_id -l /dev/sda6
  devel

  $ extras/volume_id/vol_id -t /dev/sda6
  ext3


Any comment/questions/concerns to me:
  Kay Sievers <kay.sievers@vrfy.org>