Wednesday, April 17, 2013

How to Remove HTML tags from HTML file using sed  Command

Usermod command is used to modify user account. This command is useful to change the parameters of only existing users. It can change home directory of existing user, login name, login shell, comment of passwd file etc.

We will understand usermod command with examples:

How to change home directory of existing user?

Sometimes we need to change user’s home directory with new directory but all content of old directory should have to move new directory. In this case, we need to use –m option with –d, which moves all old directory content to new directory. If we don’t want to move old directory content to new then no need to use –m option.

Test1 is already created user. We need to move old directory content to new location and set it as new home directory.
Old home directory= /home/test1
New home directory=/root/test1

root@rhel:~/ctier/shellscript# cat /etc/passwd | grep test1
test1:x:1008:1010::/home/test1:/bin/sh
root@rhel:~/ctier# usermod -md /root/test1 test1
root@rhel:~/ctier#
How to change the login shell of user?

Sometimes, we forget to mention shell while creating user. But we can change the default shell to desired as below:

root@rhel:~/test2# useradd test1
root@rhel:~/test2# su test1
$
$
$ echo $USER
test1
$
$ echo $SHELL
/bin/sh
$
$ exit
root@rhel:~/test2# usermod -s /bin/bash test1
root@rhel:~/test2# su test1
test1@rhel:/root/test2$ echo $SHELL
/bin/bash
test1@rhel:/root/test2$


Rename the user

We can change the login name of user with usermod command.  But if you change the username then it will not impact on other details like home directory, expiry date etc. It will remain same.

root@rhel:~/test2# cat /etc/passwd | grep test
test1:x:1008:1010::/home/test1:/bin/bash
root@rhel:~/test2# usermod -l login1 test1
root@rhel:~/test2# cat  /etc/passwd | grep test
login1:x:1008:1010::/home/test1:/bin/bash
root@rhel:~/test2# su login1
login1@rhel:/root/test2$

Lock user’s password

Root user can lock user’s password as well as unlock it using the usermod command. As below example, we locked user’s password by –L option through root user and then tried to switch user from normal user but couldn’t login. Again login by root user, unlock the user’s password by –U option and the tried to login then it is allowing successfully.

root@rhel:~# usermod -L login1
root@rhel:~# exit
logout
machindra@rhel:~$
machindra@rhel:~$ su login1
Password:
su: Authentication failure
machindra@rhel:~$ sudo -i
root@rhel:~# usermod -U login1
root@rhel:~# exit
logout
machindra@rhel:~$ su login1
Password:
login1@rhel:/home/test$
login1@rhel:/home/test$

Change UID of existing user

We can change the UID of existing user by usermod command. For this purpose, we need to use –u option with desired UID and it should not be used by any other user.
Old UID: 1008
New UID: 3045

root@rhel:~#
root@rhel:~# cat /etc/passwd | grep test
login1:x:1008:1010::/home/test1:/bin/bash
root@rhel:~# usermod -u 3045 login1
root@rhel:~#
root@rhel:~# cat /etc/passwd | grep test
login1:x:3045:1010::/home/test1:/bin/bash
root@rhel:~#

Change the group of user

We can change the group of user with –g option. Old group id of user login1 is 1010 and we will change it to 130 i.e. group will be rdeck.
root@rhel:~# cat /etc/passwd | grep test
login1:x:3045:1010::/home/test1:/bin/bash
root@rhel:~#
root@rhel:~# usermod -g 130 login1
root@rhel:~# cat /etc/passwd | grep test
login1:x:3045:130::/home/test1:/bin/bash
root@rhel:~#

Advanced use of sed command                                                                   Basic use of sed command
Posted by Machindra Dharmadhikari On 4/17/2013 08:20:00 PM 1 comment

1 comments:

Post a Comment

  • RSS
  • Delicious
  • Digg
  • Facebook
  • Twitter
  • Linkedin
  • Youtube

    Chitika Ads 2

    Histat

    About

    Enter your email address:

    Delivered by FeedBurner