Prompted for password twice at linux boot login
Solution 1:
There is a module in PAM that deals with user authentication called pam_unix.so. It will be mentioned in a file called common-auth or simply auth in the directory /etc/pam.d/. There may be multiple entry there or perhaps the update could have modified it in some way. Can you post the lines in the file here? If you cannot find it, you have to search for the file that is identical to common-auth in arch-linux.
You can read about pam and the modules.