- Switch Linux-PAM's pam_unix module to use sha512 for passwords hashes rather than MD5. This option requires sys-libs/pam version 1.0.1 built against sys-libs/glibc version 2.7, if it's built against an earlier version, it will silently be ignored, and MD5 hashes will be used. All the passwords changed after this USE flag is enabled will be saved to the shadow file hashed using SHA512 function. The password previously saved will be left untouched. Please note that while SHA512-hashed passwords will still be recognised if the USE flag is removed, the shadow file will not be compatible with systems using an earlier glibc version.