Remove Encryption Entirely
To reset Ambari database and LDAP passwords to a completely unencrypted state:
On the Ambari host, open
/etc/ambari-server/conf/ambari.properties
with a text editor and set this propertysecurity.passwords.encryption.enabled=false
Delete
/var/lib/ambari-server/keys/credentials.jceks
Delete
/var/lib/ambari-server/keys/master
You must now reset the database password and, if necessary, the LDAP password. Run ambari-server setup and ambari-server setup-ldap again.