change root password

i just notice only hp-ux will ask old password if you want to change the root password

$ uname -a
HP-UX hostname B.11.00 U 9000/800 146901507 unlimited-user license
$ passwd
Changing password for root
Old password:

very good security practise i must say.
the rest, linux, solaris & aix, you can simply change the root password to new one without asking the old password.

# uname -a
Linux hostname 2.4.21-32.0.1.nfswan2 #1 SMP Thu Aug 4 11:02:01 CEST 2005 x86_64 x86_64 x86_64 GNU/Linux
# passwd
Changing password for user root.
Enter new UNIX password:

# uname -a
SunOS hostname 5.8 Generic_108528-13 sun4u sparc SUNW,Ultra-2
# passwd
passwd: Changing password for root
New password:

# uname -a
AIX hostname 1 5 0045C2CA4C00
# passwd
Changing password for "root"
root's New password: