/etc/ha.d/authkeys contains pre-shared secrets used for mutual cluster node authentication. It should only be readable by root and follows this format:

auth <num>
<num> <algorithm> <secret>

num is a simple key index, starting with 1. Usually, you will only have one key in your authkeys file.

algorithm is the signature algorithm being used. You may use either md5 or sha1; the use of crc (a simple cyclic redundancy check, not secure) is not recommended.

secret is the actual authentication key.

You may create an authkeys file, using a generated secret, with the following shell hack:

( echo -ne "auth 1\n1 sha1 "; \
  dd if=/dev/urandom bs=512 count=1 | openssl md5 ) \
  > /etc/ha.d/authkeys
chmod 0600 /etc/ha.d/authkeys