### Switching Master and Slave KDCs

You may occasionally want to use one of your slave KDCs as the master. This might happen if you are upgrading the master KDC, or if your master KDC has a disk crash.

Assuming you have configured all of your KDCs to be able to function as either the master KDC or a slave KDC (as this document recommends), all you need to do to make the changeover is:

If the master KDC is still running, do the following on the old master KDC:

1. Kill the `kadmind` process.
2. Disable the cron job that propagates the database.
3. Run your database propagation script manually, to ensure that the slaves all have the latest copy of the database. (See Propagate the Database to Each Slave KDC.) If there is a need to preserve per-principal policy information from the database, you should do a "kdb5_util dump -ov" in order to preserve that information and propogate that dump file securely by some means to the slave so that its database has the correct state of the per-principal policy information.

On the new master KDC:

1. Create a database keytab. (See Create a kadmind Keytab (optional).)
2. Start the `kadmind` daemon. (See Start the Kerberos Daemons.)
3. Set up the cron job to propagate the database. (See Propagate the Database to Each Slave KDC.)
4. Switch the CNAMEs of the old and new master KDCs. (If you don't do this, you'll need to change the `krb5.conf` file on every client machine in your Kerberos realm.)