A sample in-memory realm configuration is available at /usr/share/pki/acme/realm/in-memory/realm.conf.
To use an in-memory realm, copy the sample realm.conf into the /var/lib/pki/pki-tomcat/conf/acme folder,
or execute the following command:
$ pki-server acme-realm-mod --type in-memory
The realm.conf should look like the following:
class=org.dogtagpki.acme.realm.InMemoryRealm
username=admin
password=Secret.123