afpd.service:

<?xml version="1.0" standalone='no'?><!--*-nxml-*-->
<!DOCTYPE service-group SYSTEM “avahi-service.dtd”>
<service-group>
<name replace-wildcards=”yes”>Intrepid Time Machine</name>
<service>
<type>_afpovertcp._tcp</type>
<port>548</port>
</service>
<service>
<type>_device-info._tcp</type>
<port>0</port>
<txt-record>model=AirPort</txt-record>
</service>
</service-group>

daapd.service:

<?xml version="1.0" standalone='no'?><!--*-nxml-*-->
<!DOCTYPE service-group SYSTEM “avahi-service.dtd”>
<service-group>
<name replace-wildcards=”yes”>Home Music Server</name>
<service>
<type>_daap._tcp</type>
<port>3689</port>
</service>
</service-group>

After placing these two files into /etc/avahi/services, the new services starting advertising immediately. By the way, you’ll note the extra “device-info” entry in afpd.service; that sets the icon that will be used by Macs when they discover this service. I made mine look like a Time Capsule by using the setting listed above.

During this work with Avahi, I uncovered a couple of interesting things:

• I found that restarting the Avahi daemon is actually more problematic than just leaving it alone; in order to make it start advertising services again after a restart, you’ll have to open one of the files in /etc/avahi/services and then close it again. No changes are necessary to the file, but opening it will kickstart Avahi into service advertisement.
• Advertising SMB/CIFS and AFP together with the same name caused my Mac to ignore the SMB/CIFS services and only use AFP. I had to separate SMB/CIFS and AFP into different entries. Since I was using AFP really only for Time Machine backups and SMB/CIFS for everything else, it wasn’t really a big deal.
• Advertising SMB/CIFS and RFB (Screen Sharing, as outlined here) works fine together.

At this point, task #5 was pretty much complete. I had originally envisioned providing file sharing services to the same locations via both AFP and SMB/CIFS, but in the end—partially because of the odd issue with AFP and SMB/CIFS being advertised together as described above—settled for using AFP only for Time Machine and SMB/CIFS for everything else.

Along the way, I also configured screen sharing as outlined here, and it seems to work just fine. I have to leave an account logged in to the Ubuntu server, but I can just lock the screen when I’m not logged in remotely.

The last step was to enable Time Machine backups to the Ubuntu server via AFP. First, the hack to enable non-Time Capsule network backups (this should be all on one line):

defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1

I was then able to select the Ubuntu-hosted AFP volume for Time Machine backups. Attempting to run a Time Machine, backup, however, reported an error about being “unable to create the disk image”. Fortunately, a number of different articles pointed to the use of hdiutil to create the disk image, and that seemed to fix the problem. Time Machine is now backing up to the AFP volume, although I suspect I still have a few issues to work through (for example, it looks as though I have to keep the Time Machine AFP volume mounted in order for automatic backups to run).

So, when everything is said and done, I was able to achieve all my stated goals. The only outstanding issue that I haven’t yet figured out yet centers on automatic logins; for both AFP and SMB/CIFS, I get prompted for a password when connecting, even though I keep my password synchronized (manually) between my Mac and the Ubuntu server. Any tips on how to resolve that would certainly be appreciated.

Along the way, I found the following sites to be quite helpful. I’m sure there are others that I used along the way, and I apologize if I’ve failed to extend credit where credit is due.

Limit size of Time Machine backups on Time Capsule
Set up Time Machine on a NAS in three easy steps
Make Ubuntu a Perfect Mac File Server and Time Machine Volume
Five Guides on How to Integrate Ubuntu into a Mac OS X Network
Time Machine Wireless Backups without Time Capsule

• Ubuntu on the Cloud with Virtualization
• Tutorial: Installing Google Android SDK 1.0 On Ubuntu 8.04 Desktop