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
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.
The root user can also delete a password from an account (so a user can log in with just a username):
# passwd -d jane
Removing password for user jane.
passwd: Success
This must be used carefully because it presents a big security risk. Remember that remote users may be able to connect via SSH, and then they won't need a password either!
To find out the password status of an account, use -S :
# passwd -S jane
Empty password.
# passwd -S chris