This is one of those blog posts that is getting written mostly for my future reference, but someone out there may possibly find it useful as well. Recently Mediacom, the local cable provider, decided to move around a few channels and I found myself needing to update my MythTV box so that it knew the proper channels to record my shows from. This turned out to be fairly simple. I logged into the box via ssh and executed a su command to elevate myself to the root account. Then I executed the following command:
$ mythfilldatabase --do-channel-updates
After a few minutes of updates, everything was taken care of. There was no need to reboot the computer and my records still existed unharmed.