Old ubuntu password

Question

I know how to set new password of root in ubuntu 10.04 if I don't know root pasword and grub has no password . I want to know that whether I could get the old password which was set before I changed it. Does some file or command can give me access to old password of root

Answer 1

I'm not sure whether the password is saltet. If not, a rainbow table could help you crack it.

Normally, root should not have a password on Ubuntu at all, but you should use the sudo-mechanism to do sudo-tasks.

sudo grep root /etc/shadow

will show you, whether there is or not.

For me this reveals

root:!:13874:0:99999:7:::

which means, root has no password ("!" in second field, not a long hashcode).

A weak password might be cracked by brute force. A strong, salted password would be too expensive to crack and still last years.

see

man shadow 
man 3 crypt 

for further details.