on Server A
as root user

Code:

chmod 444 /etc/shadow

on server B
as root user

Code:

chmod 644 /etc/shadow
cp /etc/shadow /etc/shadow.keep   # this is to revert if it screws up
scp me@serverA::/etc/shadow .
chmod 400 /etc/shadow

TEST several user logins on serverB. Note: Create separate processes for login testing, KEEP YOUR root PROCESS active no matter what, so if you broke stuff, you can still fix it. If you really broke things, nobody can login to serverB, including root. Use the copy /etc/shadow.keep to restore.

Go back to serverA

Code:

chmod 400 /etc/shadow

This effort will not work to duplicate passwords if you are using NIS or LDAP or you have messed with PAM setup on either box.