To use munge, you need to create a secret key file /etc/munge/munge.key,
you can run the create-munge-key script as root to generate a random
key or follow the instructions in QUICKSTART.

You need to securely propagate the secret key file (eg, via ssh) to
other hosts within the same security realm. Credentials are valid only
within a security realm (ie, on hosts sharing the same secret key). All
munged daemons exchanging credentials need to share the same secret key.

If the secret key file is created or copyed before the package is
installed, the installation script will accept the key instead of
generating a new one.