Universally Unique IDentifier or UUID is a random 128-bit value that's generated and can be assigned to partitions or block devices. The partitions or block devices could then be identified using UUID instead of the normal device name such as /dev/sda1. This can then be used to mount filesystem via /etc/fstab by specifying UUID value in block special device (the first field).

UUID normally is just a symlink to the actual device name and could be manually found within the /dev directory. You could also use specific program to get UUID for partitions or block devices from the terminal in Linux.

Steps to get disk partition UUID in Linux:

  1. Launch terminal.
  2. List content of /dev/disk/by-uuid/ via ls using long listing format.
    $ ls -l /dev/disk/by-uuid/
    total 0
    lrwxrwxrwx 1 root root  9 Aug 22  2019 2019-04-16-20-20-34-00 -> ../../sr0
    lrwxrwxrwx 1 root root 10 Aug 22  2019 84a42ad4-c261-4ed7-a428-33f648f959df -> ../../sda2

    The absolute path for ../../sda2 is /dev/sda2

  3. Run blkid command.
    $ sudo blkid
    /dev/sr0: UUID="2019-04-16-20-20-34-00" LABEL="Ubuntu-Server 19.04 amd64" TYPE="iso9660" PTUUID="73a9f942" PTTYPE="dos"
    /dev/sda2: UUID="84a42ad4-c261-4ed7-a428-33f648f959df" TYPE="ext4" PARTUUID="c373394c-81af-4e90-985e-1a51805cdf57"

    blkid is installed by default in most Linux distributions.

    More options for blkid:

    $ blkid --help
    
    Usage:
     blkid --label <label> | --uuid <uuid>
    
     blkid [--cache-file <file>] [-ghlLv] [--output <format>] [--match-tag <tag>]
           [--match-token <token>] [<dev> ...]
    
     blkid -p [--match-tag <tag>] [--offset <offset>] [--size <size>]
           [--output <format>] <dev> ...
    
     blkid -i [--match-tag <tag>] [--output <format>] <dev> ...
    
    Options:
     -c, --cache-file <file>    read from <file> instead of reading from the default
                                  cache file (-c /dev/null means no cache)
     -d, --no-encoding          don't encode non-printing characters
     -g, --garbage-collect      garbage collect the blkid cache
     -o, --output <format>      output format; can be one of:
                                  value, device, export or full; (default: full)
     -k, --list-filesystems     list all known filesystems/RAIDs and exit
     -s, --match-tag <tag>      show specified tag(s) (default show all tags)
     -t, --match-token <token>  find device with a specific token (NAME=value pair)
     -l, --list-one             look up only first device with token specified by -t
     -L, --label <label>        convert LABEL to device name
     -U, --uuid <uuid>          convert UUID to device name
     <dev>                      specify device(s) to probe (default: all devices)
    
    Low-level probing options:
     -p, --probe                low-level superblocks probing (bypass cache)
     -i, --info                 gather information about I/O limits
     -S, --size <size>          overwrite device size
     -O, --offset <offset>      probe at the given offset
     -u, --usages <list>        filter by "usage" (e.g. -u filesystem,raid)
     -n, --match-types <list>   filter by filesystem type (e.g. -n vfat,ext3)
    
     -h, --help                 display this help
     -V, --version              display version
    
    For more details see blkid(8).
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