Yosemite is renaming my computer - why?

I had the same problem on my home network with my MacBook Pro (Retina, Mid 2012).

I haven't set the -nonamechange flag yet, but most of the incrementally numbered computers went away when I turned off Wake from LAN and restarted the airport express. Apparently one of our other airports or apple tvs was holding on to one of the phantom shares because it did not go away.

Not until I saw this and a similar post on reddit did I restart everything (as sequenced above, but shutting down the computer first). This killed the phantom share that had previously remained.

I'd like to try setting the -nonamechange flag but the computer is a laptop and, if I understand what you posted previously, a static DHCP reservation set from the airport didn't work for you whit the flag set?

Thanks.

In order:

Renamed computer & hostname from Terminal: No lasting effect

Switched from static IP and reserved DHCP address on Airport Extreme: No lasting effect

Set -nonamechange flag in discoveryd plist: fixed the problem

Restarted router AND Apple TV as per Macintouch post: made no difference to me after setting the -nonamechange flag, but I suspect that the sleep proxy server in the AppleTV and/or Router may have been the actual cause of the problem

Safe to say that setting the flag and restarting my Airport Extreme AND AppleTV have stopped the name changing permanently. Restarting the router alone was one of the first things I tried, but I had forgotten that AppleTV also provided a sleep proxy for the Wake for Network Access service.

This seems to have solved it for me, thank you JD Warwick. I have an Airport Extreme, an Airport Express, and NO Apple TV with my home network NOT using the 5GHz feature. After I followed these steps its been 5 hours and no computer name changes; it used to happen every few minutes. I did not follow any other steps that I've seen listed elsewhere except that I opened Disk Utility and ran "Fix Disk Permissions". I don't know if that had any effect because I did them at the same time. Probably should have waited and taken a more scientific approach but I wanted this problem solved, so annoying!

In my opinion this is a heinous bug and it really should be fixed immediately.

For the record, these were the steps that worked for me:

1. Unplug AC power from all Apple TVs

2. Unplug AC power from all Apple routers

3. Reset the machine name in System Preferences

4. Reconnect the primary router and wait for it to boot

5. Reconnect any additional routers

6. Reconnect the Apple TVs

7. open Disk Utility and run Repair Disk Permissions (I'm not sure if this helped)

Since I can't restart all the AppleTV devices on my network, I was able to resolve this problem by turning off the "Wake for network access" option in Energy Saver preferences. I can't play media from my sleeping Mac now, but I never do that anyway.

I noticed that the most recent OS X update contained an update for Wi-Fi stability. I wonder if this is the issue being addressed.

Same issue here. I cannot believe Apple could screw up something so important. Anyone who accesses a secure network that confirms the computer name, e.g., via Citrix, is totally screwed. My wife can no longer use computer for work.