I found this for you.
"umm yeah its very easy ...
get a bootdisk (or a boot cdrom)
boot into single user mode ... mount the root partition and then edit the /etc/shadow file to be blank (ie no passwd).
btw this works for sun as well - its how you "recover" root - same thing can be done w/ windows (linux bootdisk, mount the fat/ntfs system) and then find your favourtie crack (l0pht made one? - i aint sure, don't deal with it much)
so if they have physical access - they have root
hope that helps,"
and this too,
"the process you are describing is entering into single-user mode linux. it is easily avoided however.
basically if you have physical access to the machine then u can reboot it, and when you get to the LILO prompt, type in 'linux single'. this mode does not require a password to get access to the root account, and is commonly used to reset the password if forgotten.
however if the machine has a LILO password configured, this password is needed to get access to any mode of the linux machine. the password can be added by editing /etc/lilo.conf. check 'man lilo.conf' for the exact setting.
in short, if the administrator of the linux machine is any good, then linux is rock solid. "
I hope that gets you out of trouble.