In /etc/shadow, hashed and salted passwords are stored together with the user name as follows:
myuser:$6[someSaltedHash]:...
where the number following the $ can take the values 1~6 corresponding to the following hash algorithms:
1 md5
2a Blowfish
2y Blowfish with correct 8-bit char handling
5 sha-256
6 sha-512
Many How-to's on the Internet recommend using mkpasswd from the expect package, but I find it is much easier to use python2 or python3 to generate the salted hash.
Python 2:
python -c 'import crypt,getpass; print crypt.crypt(getpass.getpass())'
You will then be prompted to enter your plaintext password after which a /etc/shadow compatible hash will be output.
Python 3:
python3 -c 'import crypt; print(crypt.crypt("yourpw", crypt.mksalt(crypt.METHOD_SHA512)))'
In this snippet, you simply enter your plaintext password as an argument and then a /etc/shadow compatible hash will be printed out on the terminal.
You can copy-paste this salted hash into a Kickstart (RHEL and variants) or DI preseed file (Debian and variants) for automated installations.
References:
https://access.redhat.com/solutions/221403 (requires registration)
http://serverfault.com/questions/330069/how-to-create-an-sha-512-hashed-password-for-shadow
