Unable to login. Does not accept password-unix_chkpasswd[1485]: check pass; user

[veerloh]

I have dual boot windows Sp2 and Fedora 8 (2.6.23.1-42,fc8).I changed my root password by the following method:
1. boot linux kernel: init=/bin/sh
2. mount -o remount,rw /
3. /usr/bin/passwd

after changing my root password it said 'Authentication token updated sucessfully'

The problem now is i am unable to login either as a root or as a normal user.I then tried the following method to change my root password.

2. booting kernel: runlevel 1 (single user mode)
passwd : It says'changing passwd for user root.
unix_chkpasswd[1485]: check pass; user unknown.
passwd : Authentication token manipulation error.

So am not able to change the password this way.
when i boot the kernel in single user mode and type command 'who' i get no response other than the prompt.when i do 'su' my prompt changes to [root@null]#
 :'(
Please guys could you help me.

[Ricky]

hmm..

Looks like it is unable to find user root itself.. or may be it doesn't have permission to do so... ?

Did you remount in rw mode after entering into SINGLE USER MODE ?
ie. boot into single user mode and then

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#mount -o remount,rw /
and then run 

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#passwd
Let me know how it goes !!!

[veerloh]

Thanks for replying. I had lost the hope of getting any reply.

Sorry to reply so late.

before i enter the single user mode, it prints
MAKE DEV: no such user as root
MAKE DEV: no such user as root

id: Cannot find name for user ID 0

After entering the single user mode i typed;

sh-3.2#mount -o remount, rw /
sh-3.2#passwd
passwd:cannot identify you!     

when i do su, it says su: user root does not exist.

I am so screwed. what should i do?
Thanks.

[Ricky]

I hv never been such situation, just guessing now..

First see if you have user root in there or not .
see by cat

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#/etc/passwd

OR

#cat /etc/shadow

If it is not there then you can do adduser..You need to make sure that user has UID 0 and GROUP 0

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#adduser -u 0 -o -g 0 -G 0,1,2,3,4,6,10 -M rootAbove, 1,2,3 ...... are extra privileges which is required by a root user (read somewhere) and -M is to not create home directory for user root as it is already there.

After that try changing password.

Btw, not to forget .. before doing any thing, mount it in rw mode.

[veerloh]

Hi,

I am able to login into the system now. Actually i modified the /etc/sysconfig/selinux to SELINUX=disabled. And then edited my /etc/password to make the following change;
root:x:0:0:root:/root:/bin/bash. So i was able to login to the system and also changed my password succesfully.

But i never actually understood the funda of 'mount -o remount, rw /' what does it do? and why is it required? cause this was the command i had used to change my root password? 

So could you please put some light on this?
Thanks for replying
 

[Ricky]

That mount command has nothing to do with your password change. Sometimes when you log into SINGLE USER MODE, the file system is mounted in Read only mode, hence to do changes you are required to mount in read/write mode. This is what I had to do recently when one of the linux I use went sour.

Btw, I am glad to see that somehow you got it fixed, but in /etc/passwd .. was there user "root" or was not at all ?

[veerloh]

Thanks for replying Ricky:)

The user root entry was present in the /etc/passwd file. The only thing missing was the ID of the user root and thats why the system also informed saying 'user root doesnt not exit'.