Linux-->Password-->Help

[redhy]

hello brothers,

This is the problem I am facing :

xdm does not start.Login prompt appears.When I try to login as root(or as any other user),it shows :

Login Failed.

I restart the system and enters into single user mode.
When i try to change the password using passwd, it shows

passwd: Can not identify you!

I tried Linux Rescue and the same message appears. (/etc/passwd file is intact). What could be the problem and solution.

Thanx in advance.

[slarty]

Maybe /etc/shadow has been corrupted somehow. I have never seen this happen but it's theoretically possible.

Instead of using single user mode, boot (for example from lilo) with the kernel command line

init=/bin/sh

This will bypass *everything* and dump you into a shell (beware, most things won't work)

Next, you need to remount the root fs read-write (as it will undoubtably be read-only at this point). Do something like

mount -n / -o remount,rw

This should make the root fs r/w. Assuming this works, try

touch /x; rm /x

which should work

Next, you can repair /etc/shadow. It's easiest to look at it using an editor (say, vi)

vi /etc/shadow

You'll see if it appears the correct structure (similar to passwd). If it doesn't seem structurally sound, copy /etc/shadow- over the top (this is a backup which gets made automatically)

Next reset root to having a blank password. Change the 2nd field of root's line in /etc/shadow to nothing, so the line looks something like

root::12092:0:99999:7:::

Although yours might look slightly different.

Exit the editor, run sync, then unmount the root fs

mount / -o remount,ro

Then hit ctrl-alt-del (ignore any messages which come up now, it's expected that there will be a lot of errors because the system isn't up running properly)

Now you should be able to login as root with no password. Then change the root
password back.

All this assumes your system uses shadow passwords (virtually no Linux system
made in the last 5 years doesn't by default)