[REPRINT]MODIFYING USER ACCOUNTS(usermod)

http://landoflinux.com/linux_usermod_command.html

Append Additional Groups to an exiting account

usermod -a -G group1,group2,group3 userid

[root@fedsrv01a ~]# id testuser
uid=1001(testuser) gid=1004(testuser) groups=1004(testuser)

[root@fedsrv01a ~]# groups testuser
testuser : testuser

[root@fedsrv01a ~]# usermod -a -G group1,group2,group3 testuser

[root@fedsrv01a ~]# id testuser
uid=1001(testuser) gid=1004(testuser) groups=1004(testuser),1001(group1),1002(group2),1003(group3)

[root@fedsrv01a ~]# groups testuser
testuser : testuser group1 group2 group3

Change a Users Home Directory

usermod -d /new/home userid

root@john-desktop:/home# grep testuser /etc/passwd
testuser:x:1003:1235:testuser:/home/testuser:/bin/sh

root@john-desktop:/home# usermod -d /home/new testuser

root@john-desktop:/home# grep testuser /etc/passwd
testuser:x:1003:1235:testuser:/home/new:/bin/sh

Change a Users Default Shell

usermod -s /bin/bash userid

The "-s" option is used to specify a shell to be used with the specified user. By default most Linux systems will assign the "Bash Shell". However, many systems often have other shells available or shells that can be installed. To display what shells are available on your system, simply issue the command: "cat /etc/shells". In the example below we are going to change the users shell from the default "Bash Shell" to the "Korn Shell".

[root@fedsrv01a ~]# grep testuser /etc/passwd
testuser:x:1001:1004:Test User Account:/home/testuser:/bin/bash

[root@fedsrv01a ~]# usermod -s /bin/ksh testuser

[root@fedsrv01a ~]# grep testuser /etc/passwd
testuser:x:1001:1004:Test User Account:/home/testuser:/bin/ksh

Change User Comment Description - ( gecos )

usermod -c "Change my comment info" testuser

[root@fedsrv01a ~]# grep testuser /etc/passwd
testuser:x:1001:1004:Test User Account:/home/testuser:/bin/ksh

[root@fedsrv01a ~]# usermod -c "Testing Account Only" testuser

[root@fedsrv01a ~]# grep testuser /etc/passwd
testuser:x:1001:1004:Testing Account Only:/home/testuser:/bin/ksh

Change a users UID

usermod -u UID testuser

This option allows you to change the "UID", a numerical value that identifies a user's account.

[root@fedsrv01a ~]# grep testuser /etc/passwd
testuser:x:1001:1004:Testing Account Only:/home/testuser:/bin/ksh

[root@fedsrv01a ~]# usermod -u 1010 testuser

[root@fedsrv01a ~]# grep testuser /etc/passwd
testuser:x:1010:1004:Testing Account Only:/home/testuser:/bin/ksh