5.16 Nulling the Root Password Without vi
5.16.1 Description:
This is a way to clear the root password when you don't have
access to the vi editor.
Example
Flavors: AT&T, BSD
If
no one has access to the root password on a system and it is a matter of urgency
to get into that system, you can boot miniroot and clear the password out of
the root account. This can be done even when the vi editor is inaccessible.
To do this on a system using the /etc/shadow file, use the ed
editor with 13 dots and your problems are solved:
# cp /etc/shadow /etc/shadow.bak
# ed /etc/shadow
1p
s/:.............:/::/
1p
w
q
Line 1: While in the ed editor, go
to the first line of the file.
Line 2: Switch the first occurrence of a field that has 13 characters
with nothing. This is the password field.
Line 3: Write out the file.
Line 4: Quit.
You're finished! You swapped out the 13 characters of root's
password field with nothing and cleared the password. You can now bring the
system to single user and change the root password. The same basic commands
can be used on the /etc/passwd file for those platforms that don't support
shadow passwords. The result is the same.
Reason
As professional UNIX system administrators, you never forget passwords.
You can use this hack in situations such as when you inherit a machine on which
there was no root password provided when you received the system, and nothing
seems to let you in.
Real World Experience
In large installations, inheriting old systems is all too common.
I remember one instance when we received a system that was running an obsolete
version of the operating system. Management wanted the data checked before it
was junked. We needed to have a CD-ROM shipped from the East Coast and had our
local sales rep hunt one down. Two weeks later we were finally ready to boot
miniroot. As we booted miniroot, the owner of the system walked in and asked
whether I wanted the root password. After everything I'd gone through,
I politely rejected her offer. I'd put so much time into this that I wasn't
going to take the easy way out now. Needless to say, I didn't need the
password from her, I gained access, and found that there wasn't anything
on the disks anyway. All in a day's work, right?
Other Resources
Man pages:
ed
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