Managing users and groups can be a tedious task, but Red Hat Linux provides a few tools and conventions to make management easier.
You can use tools like useradd or groupadd to create new users and groups from the shell prompt. But an easier way to manage users and groups is through the graphical application, User Manager. For more information on useradd and groupadd, refer to the Official Red Hat Linux Administrator’s Guide (Red Hat Press/Wiley, 2003).
User Manager allows you to view, modify, add, and delete local users and groups. To use User Manager, you must be running the X Window System, have root privileges, and have the redhat-config-users RPM package installed. To start User Manager from the desktop, click the Main Menu Button and choose System Settings > Users & Groups (or type the command redhat-config-users at a shell prompt.
10-1. User Manager: 8212; Users Tab
To view a list of all local users on the system, click the Users tab. To view a list of all local groups on the system, click the Groups tab.
Figure 10-2: User Manager — Groups Tab
If you need to find a specific user or group, type the first few letters of the name in the Filter by field. Press Enter or click the Apply filter button. The filtered list will be displayed.
To sort the users or groups, click on the column name. The users or groups will be sorted by the value of that column.
Red Hat Linux reserves user IDs above 500 for system users. By default, User Manager does not display system users. To view all users, including the system users, uncheck Preferences > Filter system users and groups from the pull-down menu.
For more information on users and groups, refer to the Official Red Hat Linux Administrator’s Guide.
To add a new user, click the New User button. A window as shown in Figure 10-3 will appear. Type the username and full name for the new user in the appropriate fields. Type the user's password in the Password and Confirm Password fields. The password must be at least six characters.
Figure 10-3: Adding a New User
The longer the user's password, the more difficult it is for someone else to guess it and log in to the user's account without permission. It is also recommended that the password not be based on a word and that the password be a combination of letters, numbers, and special characters.
Select a login shell. If you are not sure which shell to select, accept the default value of /bin/bash.
The default home directory is /home/username. You can change the home directory that is created for the user or you can choose not to create the home directory by unselecting Create home directory.
Whenever you create a new user, by default a unique group with the same name as the user is created. If you do not want to create this group, unselect Create a private group for the user.
To specify a user ID for the user, select Specify user ID manually. If the option is not selected, the next available user ID starting with number 500 will be assigned to the new user. Red Hat Linux reserves user IDs below 500 for system users. Click OK to create the user.
To configure more advanced user properties such as password expiration, modify the user's properties after adding the user. (Refer to the next section for more information.)
To add the user to more user groups, click on the User tab, select the user, and click Properties. In the User Properties window, select the Groups tab. Select the groups that you want the user to be a member of, select the primary group for the user, and click OK.
To view the properties of an existing user, click on the Users tab, select the user from the user list, and click Properties from the button menu (or choose File > Properties from the pull-down menu). A window similar to Figure 10-4 will appear.
Figure 10-4. User Properties
The User Properties window is divided into tabbed pages:
User Data — Basic user information that is configured when you add the user. Use this tab to change the user's full name, password, home directory, or login shell.
Account Info — Select Enable account expiration if you want the account to expire on a certain date. Enter the date in the provided fields. Select User account is locked to lock the user account so that the user cannot log in to the system.
Password Info — This tab shows the date that the user last changed his password. To force the user to change his password after a certain number of days, select Enable password expiration. You can also set the number of days before the user is allowed to change his password, the number of days before the user is warned to change his password, and days before the account become inactive.
Groups — Select the groups that you want the user to be a member of and the user's primary group.
To add a new user group, click the New Group button. A window similar to Figure 10-5 will appear. Type the name of the new group to create. To specify a group ID for the new group, select Specify group ID manually and select the GID. Red Hat Linux reserves group IDs lower than 500 for system groups. Click OK to create the group. The new group will appear in the group list.
Figure 10-5. New Group
To add users to the group, refer to the “Adding a New User” section earlier in this chapter.
To view the properties of an existing group, select the group from the group list and click Properties from the button menu (or choose File > Properties from the pull-down menu). A window similar to Figure 10-6 will appear.
Figure 10-6. Group Properties
The Group Users tab displays which users are members of the group. Select additional users to add them to the group and unselect users to remove from the group. Click OK or Apply to modify the users in the group.