Learn GNU/Linux Commands (9): Group - groups, id, gpasswd, groupadd, groupmod, groupdel

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In GNU/Linux, a user belongs to at least one group. A user can belong to multiple groups.

Each group has its own policy on accessing files in the system.

Users in the sudoer's group have administration privileges as root. For Fedora/CentOS/RHEL, the sudoer's group is named "wheel". For other distros, it may be named "sudo" by default.

Information about groups in the system is normally stored in "/etc/group".

Display Group membership

groups [USER]

Display which groups USER belongs to. If USER is omitted, the default is the current user. For example: 

[Texpion@com ~]$ groups root
root: root
The result is in the following format:
USER: GROUP... 

id [USER]

Display user and group information for USER, if USER is omitted, for the current user. For example: 

[Texpion@com ~]$ id root
uid=0(root) gid=0(root) groups=0(root)

Add a user to a group

gpasswd -a USER GROUP

Add USER to GROUP. If USER belongs to other groups already, GROUP becomes its secondary group.

"gpasswd" option:

  • -a, --add USER: Add USER to GROUP

Remove a user from a group

gpasswd -d USER GROUP

Remove USER from GROUP.

"gpasswd" option:

  • -d, --delete USER: remove USER from GROUP.

Make a New Group

groupadd GROUP

Change a Group's Name

groupmod -n NEW_NAME OLDNAME

"groupmod" option:

  • -n, --new-name NEW_NAME: change the name to NEW_NAME.

Delete a Group

groupdel GROUP

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