Universally Unique IDentifier or UUID is a random 128-bit value that can be generated and 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. You can then use the UUID to mount filesystem via /etc/fstab by specifying UUID value in block special device (the first field).

UUID is typically just a symlink to the actual device name in /dev directory, and you can get the UUID of a partition by browsing /dev/disk/by-uuid/ directory. There are also some command-line programs that you can use to get partition UUID in Linux.

Steps to get partition UUID in Linux:

  1. Launch terminal.
  2. List partition UUID from /dev.
    $ ls -l /dev/disk/by-uuid/
    total 0
    lrwxrwxrwx 1 root root  9 Feb  27 06:29 2020-10-22-14-30-30-00 -> ../../sr0
    lrwxrwxrwx 1 root root 10 Feb  27 06:23 9B8B-2022 -> ../../sda2
    lrwxrwxrwx 1 root root 10 Feb  27 06:23 a7d71686-0a65-4402-b6e6-b58430ef8351 -> ../../sda3

    The absolute path for ../../sda3 is /dev/sda3

  3. Get UUID for all available devices using blkid.
    $ blkid
    /dev/sda3: UUID="a7d71686-0a65-4402-b6e6-b58430ef8351" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="0ea90c96-1b56-4c51-b07a-02e09285f291"
    /dev/sr0: BLOCK_SIZE="2048" UUID="2020-10-22-14-30-30-00" LABEL="Ubuntu 20.10 amd64" TYPE="iso9660" PTTYPE="PMBR"

    blkid is installed by default in most Linux distributions.

  4. Find UUID for specific partition.
    $ blkid /dev/sda3
    /dev/sda3: UUID="a7d71686-0a65-4402-b6e6-b58430ef8351" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="0ea90c96-1b56-4c51-b07a-02e09285f291"

    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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