A partir desta fonte , no RHEL | CentOS 5:
Display Current Hashing Algorithm
Type the following command: # authconfig --test | grep hashing
Sample outputs:
password hashing algorithm is md5
Configure Linux Server To Use The SHA-512
To configure the Linux system to use the SHA-512 algorithm, enter: # authconfig --passalgo=sha512 --update
Note: users need to change their passwords in order to generate hashes using SHA-512. You can force users to change their password on next login:
# chage -d 0 userName
Eu não tentei (só tem o CentOS 4 à mão), mas espero que ajude.