Using Groups

A group is a named set of users created to enable easier file sharing among group members. By default, every user at LC belongs to a group of one with the same name as their login name, and your newly created files are assigned by default to that unique group. If you belong to other groups, you can change your default group for the current session or the group to which any of your files is assigned to take advantage of the group permissions. On LC machines, software constraints limit every user to membership in no more than 32 groups.

The table below shows how to perform the most common group-related tasks.

Group-Related Task

Command

Reveal who belongs to a specified group grep grpname /etc/group
Reveal all groups to which you belong groups
Reveal all groups to which username belongs groups username
Change your default group to grpname newgrp grpname
Restore your original default group newgrp
Change a file's group assignment chgrp grpname filename
Change a file's group permissions chmod
Create or join a group at LC

Contact LC Hotline

Your group membership on LC's archival storage systems (storage.llnl.gov) may differ from your group membership on LC's production machines, which may also often differ among themselves. You can use group assignments to control the sharing of stored files, but only if you discover who belongs to which storage groups, and only if you assign a file to a group after you store it. (Group assignment does not persist during file transfer.) You can change the group to which a stored file is assigned by using chgrp in NFT or quote site chgrp in FTP, but only if you belong to the target group. Note: Despite its name, NFT's group command begins asynchronous file transfers and has nothing to do with managing file permission groups.

To create, delete, or change the membership of a group on any OCF or SCF machines, please go to our forms web page at https://lc-idm.llnl.gov/idm/user/login.jsp.