Linux: Resetting a user’s password

Posted on in Categories , , , , , , , last updated November 26, 2007

Q. How do I reset a user’s password under any Linux distribution from command prompt?

A. To reset a user’s password, use passwd command. You have to change it to a different password.

Login as the root user

Open terminal or shell prompt

Type the following command:
# passwd username
For example, reset a tom’s password, enter:
# passwd tom
Type a new password twice.

Freebsd changing password

Posted on in Categories , , , last updated August 6, 2007

Q. How do I change a password under FreeBSD or Linux (UNIX) operating systems?

A. The FreeBSD passwd utility changes the user’s local, Kerberos, or NIS password. If the user is not the super-user, passwd first prompts for the current password and will not continue unless the correct password is entered.

Choosing a good password

It is a good idea to change password once a month or week. Make sure you change the password when admin gives you first time account information including a password to log on.

  1. The new password should be at least six characters long and not purely alphabetic.
  2. Its total length must be less 128 characters.
  3. The new password should contain a mixture of upper and lower case characters
  4. In all other situations, numbers, upper case letters and meta characters are encouraged.
  5. It should not be similar to the login id
  6. Please note that all UNIX / BSD / Linux password are case sensitive

Changing your own password

Just type passwd and hit [Enter] key:
$ passwd
So before the password can be changed, the current password must be supplied. When entering the new password, the characters entered do not echo, in order to avoid the password being seen by a passer-by. The passwd utility prompts for the new password twice in order to detect typing errors.

Changing other users password

You must login as the root user. To change password for user tom, enter:
# passwd tom

A note about passwd command

passwd command works with all UNIX, Linux, BSD and UNIX like oses. For more information read passwd man page:
man passwd

Linux reset forgotten root password

Posted on in Categories , , , , last updated September 19, 2007

Q. I forgot my root password, how can I get into my system?

A. You can reset forgotten root password under Linux by booting system into single user mode or emergency mode (also known as rescue mode).

My boot loader is GRUB (see LILO boot loader below)

)Following is the procedure to reset root password if you are using GRUB as a boot loader:

  1. Select the kernel
  2. Press the e key to edit the entry
  3. Select second line (the line starting with the word kernel)
  4. Press the e key to edit kernel entry so that you can append single user mode
  5. Append the letter S (or word Single) to the end of the (kernel) line
  6. Press ENTER key
  7. Now press the b key to boot the Linux kernel into single user mode
  8. At prompt type passwd command to reset password:

You need to mount at least / and other partitions:
# mount -t proc proc /proc
# mount -o remount,rw /

Change the root password, enter:
# passwd
Finally reboot system:
# sync
# reboot

My boot loader is LILO

At LILO boot loader type linux single and press [ENTER] key:
Boot: linux single
When you get the # prompt you will need to type passwd root to reset password:
# passwd
Reboot system:
# sync
# reboot

See also:

Linux: Delete user password

Posted on in Categories , , , , , last updated September 6, 2007

Q. How do I delete user Password under Linux? I’d like to disable a password for an account.

A. All user encrypted passwords are stored in /etc/shadow file. The quick way to remove/delete a user password is pass –delete option to passwd command. First, login in as a root user.

Command to delete user password under Linux

Type the following command to delete a user password:
# passwd --delete username
OR
# passwd -d username
Above command delete a user’s password (make it empty). This is a quick way to disable a password for an account. It will set the named account passwordless. User will not able to login. It is also a good idea to setup user shell to nologin to avoid security related problems:# usrmod -s /sbin/nologin usernameFor example to delete password for user sweta, Type:# passwd -d sweta
# usrmod -s /sbin/nologin sweta

See also: