Chris Tyler - Fedora Linux

The value of password aging is debatable; while it does limit the time that a compromised password can be used, forcing a user to change her password too frequently can make it difficult for her to remember the current password, leading to unsafe practices such as writing passwords on sticky notes or choosing weak passwords.

To delete a user account, click on the username and then click on the Delete icon. You will be warned if the user account is active (i.e., if the user is logged in or has processes running), and you will be asked for confirmation. The confirmation dialog has a checkbox that controls whether the user's files will be deleted along with the user account. If you are planning to keep the user's files, it may be better to lock the account than to delete it, so that the user's name continues to show up as the owner of those files (if the account is deleted, the account number is shown instead of the name).

The Group tab of the User Manager window works in exactly the same way as the Users tab. The only fields that appear in the Add Group dialog are for the group name and, if you want to set it manually, the group number. The Properties dialog adds a tab that shows you a list of all of the users on the system, with checkboxes to indicate which ones are in the group.

Fedora provides six utilities for managing users and groups from the command line. For users, there are useradd , usermod , and userdel ; for groups, there are groupadd , groupmod , and groupdel .

The express way to add a user is to use useradd and then set the new user's password using passwd :

# useradd jane

# passwd jane

Changing password for user jane.

New UNIX password:

bigSecret

Retype new UNIX password:

bigSecret

passwd: all authentication tokens updated successfully.

useradd accepts a number of options; the most common are shown in Table 4-12 . Most of these options can also be used with usermod to change an existing user's options.

Table 4-12. useradd options

To set Jane's full name when her account is created, execute:

# useradd -c " Jane Smith " jane

usermod works in a similar way to useradd , but is used to adjust the parameters of existing accounts. For example, to change Jane's full name:

# usermod -c " Jane Lee " jane

As you'd expect, the userdel command deletes a user. The -r option specifies that the user's home directory and mail spool ( /var/spool/mail/ user ) should also be removed:

# userdel -r jane

The groupadd , groupmod , and groupdel commands are used in a similar way to create, modify, and delete groups.

To add a group, just specify the name as an argument to groupadd :

# groupadd groupname

The only option commonly used is -g , which lets you manually select the group ID (useful if converting data from an old system):

# groupadd -g 781 groupname

The groupmod command is rarely used, but it will change the numeric group ID ( -g ) or the name ( -n ) of an existing group:

# groupmod -g 947 groupname

# groupmod -n newname groupname

To delete a group, use groupdel :

# groupdel groupname

passwd is used to set a user's password. Used by a normal user, it sets that user's password by asking for the current password and then asking for the new password twice:

$ passwd

Changing password for user chris.

Changing password for chris

(current) UNIX password:

bigSecret

New UNIX password:

newSecret

Retype new UNIX password:

newSecret

passwd: all authentication tokens updated successfully.

When used by the root user, passwd can be used to change the root password (the default) or any existing user's password if the username is supplied as an argument. You don't need to know the current password:

# passwd

Changing password for user root.

New UNIX password:

topSecret

Retype new UNIX password:

topSecret

passwd: all authentication tokens updated successfully.

# passwd jane

Changing password for user jane.

New UNIX password:

superSecret

Retype new UNIX password:

superSecret

passwd: all authentication tokens updated successfully.