change user account password

[garry_3peace]

I have a little problem here. From what I've learnt at internet to change the user account's password is like this (the user name is guest) :

usermod -p password guest

But somehow, it still didn't change the password. Additional question, if we want to create a new account, we just need to type this, isn't

useradd guest -p password

Is there any mistakes on the syntax?

[TuxKnight]

Try this

As root run the following command

passwd guest

This worked ok
useradd guest -p password

[vsemaska]

If you use usermod to change a user's password the -p option requires you pass the encrypted password. That's why it didn't work, you didn't encrypt the password.

As TuxKnight suggested use the passwd command to change the user's password.

[oz]

Here's a HowTo you can check for resetting both, root and user passwords:

http://www.linuxforums.org/forum/lin...-password.html

[garry_3peace]

oh thanks everyone. Btw how do we get encrypted password then? Let's say if I want to use usermod -p , what should I do?

[Cabhan]

If you wanted to have an encrypted password, you're basically doing what the passwd tool does. Basically, given a string, you first select your encryption mechanism: either DES or MD5.

You then need to generate what is called a salt. This is a random sequence of characters that will be used to encrypt the password. You then employ the chosen encryption algorithm using the salt and the password to generate an encrypted password.

The only time that I've ever done this was for kicks and giggles, and it's fairly simple to use glibc functions for it (except for generating a secure salt: that's more complicated).

[vsemaska]

You could use perl's crypt function to encrypt a password. Here's a very simple example:

#!/bin/bash -vx

tmp="`perl -e 'print crypt("abcdefg",756);'`"
usermod -p "$tmp" test

The password is "abcdefg" and the salt is 756. You could use $RANDOM for the salt if you want.

[garry_3peace]

Ah.. I see..
but there is something I don't understand. The result of DES mechanism surely is different with MD5 isn't it? Let say I encrypt with DES mechanism, how can the Linux know that the password argument that I give is using DES Mechanism not MD5. Btw, when I login, I type the plain text, Linux need to convert it to the encrypt text first before comparing the word right?

[vsemaska]

To the best of my knowledge Linux uses only DES in encrypting passwords. Perl's crypt function uses DES.

Linux Online - Password Security and Encryption

Not sure what Cadhan was talking about wrt MD5.

[garry_3peace]

I read man, it said it can be md5, if we configure the pam. Talking about pam, is that a program? I have a little problem on that thing(I have posted it at Redhat).

Anyway thanks for the link.