While fighting with DB2 denying logins I had to change the default hash algorithm used to store passwords in /etc/shadow.
As far as I know (and as
grep -i -r "sha512" /etc/* tells me
), there are two files that carry this information.
To change the algorithm from sha512 (which shifts as the default in the new Ubuntu releases) change this:
password [success=1 default=ignore] pam_unix.so obscure sha512
password [success=1 default=ignore] pam_unix.so obscure md5