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SubjectRe: Single user mode
> > 
> > George B. Winston IV wrote:
> Sorry for the lame question, but I think my system was hacked and all
> of the passwords changed. I can't even log-in as root.
> Is it possible to boot in single user mode and change root's
> password? If so, How do you boot in single user mode and change

Some distributors execute /bin/sulogin in "single user" mode so you
will be challenged for a password even in single user mode. This
will prevent you from logging in.

If you have SCSI, the problem that you describe is easy to fix. You connect
your root hard disk to another Linux machine, mount it off from /mnt and
fix any problems. You also might be able to do this with some IDE drive

Otherwise, most distributions provide a boot disk that can be used to
repair a damaged file-system. Usually there is some way to exit to a
shell and perform whatever commands are necessary.

In your case, the idea is to mount the "previous" root file-system read/write
and edit /etc/passwd. Just remove the root password, i.e., "::" instead of
the ":JUNK:" that presently exists. If you use shadow passwords, you also
have to execute pwconv to make the change take effect and pwconv only works
on the "real" password file. Therein lies the problem. In this case, you
have to rename the old password file (to save it) and the shadow file.
Then copy the ones from your distribution disk.

The most common reason why one can't log onto their own system from any
account is that, from a previous edit of the password file, a BLANK LINE
was accidentally put in the first record of /etc/passwd. You may find
that your system was not hacked at all. Instead, you may have added an
account and, while editing the file, accidentally included a blank line
as the first element in the file! I don't know if this is a BUG or

I spent several hours making a root file-system on a floppy. No RAM disk,
just a floppy (yes it can be done). The time spent was worth it. I can
break into any of my systems. Once you get "up", you might want to do
the same thing. If you need such a root file-system, send me private email
and you can download it from one of my servers, you would just copy the
binary file directly to a 1.44 Mb floppy, make a boot disk that expects
to mount /dev/fd0 as the root file-system... and away you go.

Dick Johnson
Richard B. Johnson
Project Engineer
Analogic Corporation
Voice : (508) 977-3000 ext. 3754
Fax : (508) 532-6097
Modem : (508) 977-6870
Ftp :
Email :,
Penguin : Linux version 2.1.21 on an i586 machine (66.15 BogoMips).
Warning : It's hard to remain at the trailing edge of technology.

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