Yosemite is renaming my computer - why?

• turn off your router
• change name
• start router

It seems to be a bug in the sharing preferences. Mine is doing the same, but it doesn't seem to be effecting anything, just annoying.

Hopefully will be fixed in the next update, in the meantime, you should tell Apple about it here https://www.apple.com/feedback/macosx.html

This is not a small deal. It is a big deal… this remaining of the computer(S) is causing Time Machine to fail and create entirely new backups and that's not what I want to happen... It's even a bigger deal when you maintain over 30 Macs...

This Yosemite update has so many bugs I need a can of raid

That has sorted out the problem. Actually I only had to restart the apple time capsule. Cheers for that. Simple and effective...

david

Restarting my airport extreme and my time capsule only fixed the problem temporarily.

Well, 13 has been appended to my computer name. It's now reported as "(My name) Macbook Air (13)" which is more than a little confusing since it's a Macbook Air 11".

Experiencing the same thing. Have tried everything to rectify the situation, but my computer name and local addressing keep changing. Be sure to log the bug so Apple can get this fixed: http://www.apple.com/feedback/macosx.html

Still the same here happening on all of my 3 Macs on Yosemite (never before under Mavericks, and before.).

None of the proposed tricks helped. Resetting the host name in preferences > sharing helps for a while but suddenly iterations appear again (2), (3), etc. on all machines in my LAN.

It really drives me nuts here!

HHave you tried switching wake up for network access. Read somewhere that it sees a ghost of the computer on the network. Worked for me.

Thank you for your suggestion. Do you mean to disable the 'wake for network access' in the 'system preferences' > 'energy safer' settings?

I will give it a try so.

This appears to be an mDNS or Bonjour issue where the computer sees a ghost of itself and changes its name. Then, depending upon whether you have a static IP address or not, you get a "this IP address is already in use message" and/or an incremented computer name. Time Machine backups start messing up saving "iMac (2), iMac (3) etc. Even if TimeMachine appears to work, you will find you cannot go back in time past the last name change.

The only fix I have found and it has stuck for three days now is to modify the .apple.discoveryd.plist to include the -nonamechange flag using Terminal (all one line):

sudo /usr/libexec/PlistBuddy -c "Add :ProgramArguments: string --no-namechange" /System/Library/LaunchDaemons/com.apple.discoveryd.plist

You can optionally also (re)set the computer name and host name from Terminal:

sudo hostname YOURHOSTNAME

and

sudo systemsetup -setcomputername YOURCOMPUTERNAME

After applying this plist change, I have "Wake for Network Access" enabled with no issues. I use static IP addressing but did try switching to DHCP and reserving an address, but no joy there for me.

Thanks a lot JD !

I added that string to the .plist according your suggestion. Using static IP addressing on all my computers ever since here either. Having "Wake for Network Access" enabled too.

Hope it helps and will let you know.

Found on MacinTouch; while setting the -nonamechange flag might stop it, this might be the cause of the problem

Antonio Tejada wrote

To the various readers with the problem of their computer name growing a parenthetical number: I had this, too, and I think I found the solution.

OS X appends the number to the machine name when it encounters another device already using that name. So, if you've only got one machine with that name, what else could be using it?? Enter Bonjour Sleep Proxy. This is a service that lets your Macs go to sleep, but their services continue to be offered via Bonjour. (When the Mac goes to sleep, the Sleep Proxy server masquerades as the Mac, continuing to advertise its services. If something tries to connect to the masquerade Mac, the Sleep Proxy server wakes the Mac, hands it its machine name back, and hands it the request to handle.) Apple routers do this, as do Apple TVs (if they don't already find another Sleep Proxy server).

My hunch is that everyone affected has an Apple router or Apple TV, as I do, and that for some reason, it's gotten out of sync and has continued to advertise the Mac's services even though it has already woken up.

So I tried this, and it worked:

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