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password recovery

Mukesh Prajapati
Greenhorn

Joined: Feb 02, 2011
Posts: 10
hello Ranchers how are you? I am new on ubuntu linux 10.10 version.I have my ubuntu password can you explain me hoe to recover my linux password .please
Andrew Monkhouse
author and jackaroo
Marshal Commander

Joined: Mar 28, 2003
Posts: 11481
    
  94

Can you please explain what you are trying to do? If you have your Ubuntu password, then you have a Linux password (Ubuntu is a flavor of linux).

Most systems are designed so that passwords are not recoverable. However it may be possible to set a brand new password on an account.


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Tim Holloway
Saloon Keeper

Joined: Jun 25, 2001
Posts: 16145
    
  21

The standard password configuration for virtually all modern-day Linux distros uses a one-way encryption scheme.

In other words, when you login, it does not decrypt the password stored in /etc/passwd (or more usually /etc/shadow). Instead, it encrypts the password you typed in and compares it to the encrypted password in /etc/passwd or /etc/shadow. Because the algorithm being used is encrypt-only (no decryption), you cannot recover a lost password. About as close as you can get is to mount a dictionary attack, and Linux also has provisions in it to make dictionary attacks as inconvenient as possible, since Bad People would otherwise use that method to break in.

So rather than recovering a password, what you need to do is reset the password to a known value. That has to be done by the system administrator.

If you lose the root password, that's a bigger problem, since you need to be logged in as root in order to issue the passwd command in most cases. To recover from that problem, you'd have to shutdown the machine, boot up into single-user mode (which doesn't require a login) and reset the root password. Then reboot into the normal operating runlevel.


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Stefan Wagner
Ranch Hand

Joined: Jun 02, 2003
Posts: 1923

Tim Holloway wrote:If you lose the root password, that's a bigger problem, since you need to be logged in as root in order to issue the passwd command in most cases. To recover from that problem, you'd have to shutdown the machine, boot up into single-user mode (which doesn't require a login) and reset the root password. Then reboot into the normal operating runlevel.


On ubuntu, there is no root login by default. All you do you do as user via sudo, and for sudo you need your own password.

However, you're right in the advice to do a (S)uperuser boot. You do it by booting from grub an entry, marked as ... (recovery mode)


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