Red Hat Enterprise Linux 5 Administration Unleashed

Managing Groups 211TABLE 9.3 ContinuedCommand-Line OptionDescription-m Minimum number of days between password changes. 0 allowsuser to change password as many times as he wants.-M Maximum number of days between password changes, after whichthe user will be forced to change password before being allowed tolog in again.-W Number of days before password change is required to warn userof upcoming password expiration.Deleting UsersThe userdel command is available for deleting users using the userdel syntax. If no command line options are used, the user is deleted and can no longer loginto the system. The private user group for the user is also deleted, and the user isremoved from any other groups of which he was a member. However, the user’s homedirectory and any other files the user owned are not deleted from the system.To remove the user’s home directory and mail spool, use the userdel -r command. All other files owned by the user must be deleted manually if the administratorneeds them removed. However, use caution when removing files owned by a removeduser, they might be shared files still needed by others in the group.Managing GroupsAs previously mentioned, a new group with the same name as the user is created bydefault when a new user is added. This new group is referred to as a private user group.Every user has a default group, which is usually the user’s private user group, but everyuser can also be a member of more than one group. When a file or directory is created bya user, the user’s default group becomes the group associated with the file unless thedirectory is configured to with the s option to chmod that sets the group ID of files in thatdirectory upon creation. The additional groups a user is a member of allows the user tohave access to files associated with the group and with the proper group file permissions.A unique integer known as a GID is associated with each group. GIDs below 500 arereserved for system groups just like UIDs below 500 are reserved for system users.9To start the graphical application for managing users and groups, select Administration,Users and Groups from the System menu on the top panel of the desktop, or execute thecommand system-config-users. If the program is run as a non-root user, enter the rootpassword when prompted. As shown in Figure 9.4, select the Groups tab to view all existinggroups.By default, system groups are not displayed in the list. To show system users in the list,select Preferences, Filter system users and groups.