My iMac's computer name keeps changing automatically after Yosemite upgrade

mine is slightly different, it seems to have changed my network name now my network name is different (by one character) to my computer name. Its true for my iPad as well (and the same character).

Could the network name be restricted in some way?

Oh crap. It's back.

Markisttoll's suggestion

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

stopped ny iMac's computer name changing, but 'computer name (2)' and 'computer name (3)' still keep appearing on the network.

That sounded good, but didn't work. After repairing disk permissions, clicked on sharing and I could watch my computer name change from iMac to iMac (2). But for some reason, I was able to get my Macbook to quit changing the name, but I have no idea why. All I did there was change the name back to MacBook and then turn the wifi off and back on again, and it hasn't changed name since, but that doesn't seem to work with the iMac.

That seemed to work! I turned off SMB file sharing and then watched by computer name change right in front of me. Then I changed it again, turned off file sharing and then turned it back on, and the name did not change again. So far so good. What a hassle.

Well, a few days later and the rename is sticking. Have no idea what prompted the issue, again; hadn't done anything that I know of. Maybe an app update or two.

All I did this time to fix was change the name in Sharing and then repair permissions, all without Safe Mode or reboot.

Still a pernicious OS X Yosemite bug I'd say.

This fixed my problem.

Thank you!

You are my hero!

Thank you for taking the time to provide a detailed step-by-step guide.

This has been affecting me for months and I was annoyed at the long

shopping list of useless shared devices... Now all is great.

Oops, sorry!

I'm grateful to everyone

but it was Chikiko's heroic step-by-step process I followed

that completely solved my problem and erased the list of unwanted devices in the sidebar.

I didn't try any other remedies suggested except I decided to verify and correct disk permissions

and repair disk in between before restarting.

(Just to clarify in case others are still having issues and decide to act on my recommendation).

JFK

What appears to have worked for me was to go to Users & Group Preferences and delete older no longer used shared users.

Thanks, Chikiko, this solution seems to have worked for me!

My Mac Mini had maxed out with (11) and I had half a dozen listings under Shared in Finder. Similar to Chikiko's situation, my problem seems to have started when I switched ISPs. That's when I started using the ISP's modem/router to create a wireless network and connected my Time Capsule to my Mac Mini via Ethernet in bridge mode as an external hard drive. I followed Chikiko's steps and the computer name isn't changing anymore and the extra listings under Shared disappeared.

By chance are you using wifi and a wired connection at the same time? OS X periodically changes the sharing name when a Mac discovers itself via traffic from one port to the other. It mistakes itself for another Mac already using the sharing name and alters the name. I believe you can see when this happens by searching your system logs for "already in use."

The behavior started with one of the last Mavericks updates before the release of Yosemite, and it continues with both releases.

For me, leaving wifi disabled eliminated the problem. It's not a great solution, however. It means Apple Maps, etc constantly pop up dialogs telling me to turn on wifi for better positioning accuracy. Unfortunately I can't turn wifi on and not join my network to avoid the problem either, as wifi connection preferences are synced between my Mac and iPhone as long as I have password sync on.

McGroarty wrote:

By chance are you using wifi and a wired connection at the same time? OS X periodically changes the sharing name when a Mac discovers itself via traffic from one port to the other. It mistakes itself for another Mac already using the sharing name and alters the name. I believe you can see when this happens by searching your system logs for "already in use."

The behavior started with one of the last Mavericks updates before the release of Yosemite, and it continues with both releases.

For me, leaving wifi disabled eliminated the problem. It's not a great solution, however. It means Apple Maps, etc constantly pop up dialogs telling me to turn on wifi for better positioning accuracy. Unfortunately I can't turn wifi on and not join my network to avoid the prEs, oblem either, as wifi connection preferences are synced between my Mac and iPhone as long as I have password sync on.

If this is the root cause of this issue (and this does seem to be evident in the system logs) then I suspect this is a DHCP/sleep problem* combined with the ARP table becoming populated with duplicate** entries.

tl;dr

1. Make sure all active network interfaces on your Mac have DHCP-reserved (or static) IP addresses.

2. Check the ARP table for duplicates** and clean if necessary

* Device1 goes to sleep with a dynamically assigned IP address; DHCP lease time expires and Device1's IP address is released back into the pool; Device2 joins network and is given Device1's IP address; Device 1 wakes up and is told that its IP address is "already in use".

** run "sudo arp -a", and make sure you're reading the table correctly - what you're looking for is your Ethernet and/or Wifi MAC address appearing more than once with different IP addresses. Or, the same IP address mapped to two different MAC addresses.

Just got off the phone with Apple support, where they suggested the following fix:

1. Go to System Preferences > Sharing and manually fix the computer name.

2. Reboot, and go back into System Preferences to check that the computer name is still what you want it to be.

3. Assuming it is, go to System Preferences > Network.

4. Create new location (e.g. home2). Optionally, delete any other locations (so you don't go back to them later).

5. Hit done, then apply. The computer should automatically reconnect to the network.

6. Reboot, and then verify the computer name one more time.

I asked him about the files in /Library/Preferences/SystemConfiguration/ and he basically said:

Yeah, that's where they are, but don't mess with them manually, because these files all work together and it's easy to mess things up. In fact, Apple doesn't even give the document (that describes how to do it manually) to their tech support employees anymore since it's way easier to just do the location stuff above and create a fresh set.

He also said that if it doesn't work, call back and they'll help resolve the issue.

For what it's worth, even though it seems like it's an OS X bug, if you tell them your device is an Airport router they'll direct your call to the people who know about this issue. The first time I called, I tried reporting it as a Mac issue and they were a bit confused.

Go to system preference>Sharing and then you can change the computer name. It will fix it for a while.