Fedora Linux

-G grp1,grp2,...	Supplementary group membership
-M	Don't create a home directory	useradd only.
-m	Create a home directory if it doesn't exist	This is the default action.
-p cryptpass	Set encrypted password to cryptpass	Useful when copying accounts from an old system configuration.
-s shell	Sets the user's shell to shell
-u uid	Set the numeric user ID to uid	Useful when copying accounts from an old system configuration or synchronizing with old NFS servers.
-L	Lock account against login	usermod only.
-U	Unlock account and permit login	usermod only.

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

4.7.1.4. Managing user passwords from the command line

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