Sometimes the need arises that one would need to set a password to disallow anyone else boot the system without correct password. This can be easily done when using GRUB as a loader. First boot your linux system. The enter grub's command prompt:
# grub GNU GRUB version 0.97 (640K lower / 3072K upper memory) [ Minimal BASH-like line editing is supported. For the first word, TAB lists possible command completions. Anywhere else TAB lists the possible completions of a device/filename. ] grub>
then type a md5crypt command which will ask for your password and spit out its equivalent in md5 encrypted version:
grub> md5crypt Password: **** Encrypted: $1$A9NHZ/$N.6k9riAFMbV/nfsZ2LnD1
Now depends on your Linux distribution locate and edit a grub's config file.
NOTE:GRUB's config file can be located at various places
Add your MD5 encrypted password to a grub's global configuration:
timeout 5 color cyan/blue white/blue password --md5 $1$A9NHZ/$N.6k9riAFMbV/nfsZ2LnD1
save and reboot.