Unix groups

UNIX groups are useful for sharing file and directory permissions with other users in the UMIACS system. Each UMIACS account is by default a member of its own group, defined by that username. An account can be made member to any number of additional groups.

Creating Groups & Adding Users

A user may create up to 5 UNIX groups via the Directory tool.

1. Click Create UNIX Group on the Groups page
2. Enter in the group name and a brief description of what the organization of users in the group is for, then click create group.
3. Click on the link of the newly created group, add a valid UMIACS user into the available text box, click add user. NOTE: The user creating the group is not added to that group by default, and must be explicitly added after creation.

Applying the Group

• In order to apply the group to a file or directory to which you want to grant all members some set of permissions use the command

chgrp group-name file-name

This will grant the specified group ownership of the file, at the level of access that the previous group possessed.

Verifying and Changing Group Permissions

• To see the permissions that the group has for a specific file/directory use ls -l and the group permissions will be the 5,6,7th characters of the permissions listing.
• To change the permissions of the group on that file/directory, if you own the group, use

chmod g+r/w/x file-name

• To access a directory, both the r and x permission bits must be set on the directory.

Deleting Groups

Deleting groups will be managed by UMIACS staff. If you would like to delete a group, please submit a ticket through JIRA.