Linux id Command - Print user ID and group ID information

December 21, 2013 | By
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To log in into a computer, we need a username. Username is an identity to recognized by a computer. Based on it, computer will apply a set of rules to a someone that log in with that username. On Linux system we can use id command.

What is id command

id command is command which can print real and effective User ID (UID) and Group ID (GID). An UID is a single identity for a user. While Group ID (GID) can consist more than one UID.

How to use it

By default, id command is installed on most of Linux system. To use it, just type id on your console. Typing id without no options will result as below. The result will use the active user.

$ id

Default id output

Here’s how to read the output :

  • User pungki has UID number = 1000, GID number = 1000
  • User pungki is a member of the following groups :
    1. pungki with GID = 1000
      adm with GID = 4
      cdrom with GID = 24
      sudo with GID = 27
      dip with GID = 30
      plugdev with GID = 46
      lpadmin with GID = 108
      sambashare with GID = 124

    Using id with options

    There are some options that can applied to id command. Here’s some options that may useful on day-to-day basis.

    Print user name, UID an all the group to which the user belongs

    To do this, we can use -a option

    $ id -a

    -a option

    Output all different group IDs (effective, real and supplementary)

    We can use -G option to do fulfill this.

    $ id -G

    -G option

    The result will only show the GID numbers. You can compare it with /etc/group file. Here’s a sample of /etc/group content :

    root:x:0:
    daemon:x:1:
    bin:x:2:
    sys:x:3:
    adm:x:4:pungki
    fax:x:21:
    voice:x:22:
    cdrom:x:24:pungki
    floppy:x:25:
    tape:x:26:
    sudo:x:27:pungki
    audio:x:29:pulse
    dip:x:30:pungki
    www-data:x:33:
    backup:x:34:
    operator:x:37:
    sasl:x:45:
    plugdev:x:46:pungki
    ssl-cert:x:107:
    lpadmin:x:108:pungki
    saned:x:123:
    sambashare:x:124:pungki
    winbindd_priv:x:125:

    Output only the effective group ID

    Use -g option to output only the effective group ID

    $ id -g

    -g option

    Print the specific user information
    We can output a specific user information related UID and GID. Just put the user name after id command.

    $ id leni

    leni user

    Above command will print UID and GID of user named leni.

    Conclusion

    This id command is useful for us when we want to know about UID and GID of a user. Some applications may need UID / GID to be run. id make us easier to find UID and GID of a user without seeing and searching it inside /etc/group file. As usual you can go to id manual page by typing man id from your console to explore more detail.

    Filed Under : LINUX COMMANDS, LINUX HOWTO

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