Managing groups is a core part of controlling who can do what on a Linux system, since groups let you hand a set of permissions to several users at once rather than one by one. This guide covers the everyday tasks: viewing group membership, creating a group, adding and removing users, and giving a group access to a directory.
Viewing Group Membership
To see which groups a specific user belongs to, pass their username to the groups command, replacing exampleuser with the name you want to check:
groups exampleuserRun it with no argument to see the groups for your own current user:
groupsCreating a Group
Create a new group with groupadd, replacing sharedgroup with whatever you’d like to call it:
sudo groupadd sharedgroupAdding a User to a Group
Add a user to a group with usermod. The -a is important, since it appends the group rather than replacing all the user’s other groups, and forgetting it is a common way to accidentally remove someone from everything else:
sudo usermod -a -G examplegroup exampleusernameGiving a Group Access to a Directory
To let a group share a directory, set the directory’s group ownership with chown. The -R applies it recursively to everything inside:
sudo chown -R :examplegroup sharedfolder/Removing a User from a Group
To take a user back out of a group, use gpasswd with the -d flag:
sudo gpasswd -d testuser testgroupWith these few commands you can organise users into groups and manage shared access cleanly, which is far easier to maintain than setting permissions on individual users one at a time.
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