Linux-->Password-->Help
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Thread: Linux-->Password-->Help

  1. #1
    Junior Member
    Join Date
    Jan 2002
    Posts
    25

    Linux-->Password-->Help

    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.

  2. #2
    Senior Member
    Join Date
    Jan 2002
    Posts
    1,207
    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
    Code:
    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

    Code:
    mount -n / -o remount,rw
    This should make the root fs r/w. Assuming this works, try

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

    Although yours might look slightly different.

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

    Code:
    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)

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