bash history for root user...

Check in /var/root for the file .bash_history. If it's not there, find out what is root's home directory with

finger root

To clear the file, the commands


sudo -H bash
HISTFILESIZE=0; rm ~/.bash_history; exit


should do the trick.

jarik

/var/root is definitely root's home directory, but I can find no history file there. BTW, sudo -H bash will not change to the home directory, you need to also cd after it.

So where is root's history kept?

I assumed that the OP knew that his problem (passwords) were in root's history.

Unless you have a habit of running sudo with -H or if you have root logins enabled, root shares your settings (since sudo without -H keeps the original user's HOME) and runs .bashrc from the original user's HOME, saves history in there etc.

Quick test with:
host user $ sudo bash
Password:
host user # echo hello_world
hello_world
host user # exit
host user $ grep hello_world .bash_history
echo hello_world
host user $

jarik

That makes a lot of sense. It was what I suspected at first, and yet root's history didn't seem to match with my own. Then I remembered my default shell at login is tcsh and that was what root was using! Duh!

Anyway I think you solved the OP's problem.