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Whenever I join a network where there are other Macs, I sometimes get the notification:

This computer's local hostname Macintosh.local is already in use on this network. The name has been changed to 'Macintosh-2.local`.

From then on the result of hostname is this changed name. I've tried:

  • System Preferences->Sharing->Computer Name.
  • sudo hostname jared-mac.
  • Modified /etc/hostname.
  • System Preferences->Network->Advanced... ->TCP/IP DHCP Client ID
  • System Preferences->Network->Advanced... ->WINS

Is this a known issue? Or am I doing something wrong?

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I actually have encountered the same issue a few times, using a very unique computer name... (I did not try to disable IPV6 like suggested in one of the links above, as it does not really bother me.) – Arjan Jul 11 '09 at 20:08
up vote 4 down vote accepted

Normally the two are in sync, but you can alter the hostname by going to:

System Preferences -> Sharing -> Under Computer Name on the right side is an Edit button. Click the Edit button and in the new sheet alter your hostname to match your computer name.

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So when your hostname is "jared-mac" it is reverting to "Macintosh-#" - even if the hostname of the other Mac is not the same? – Chealion Jun 12 '09 at 5:49
@Chealion, you are right. You have to press the Edit button which presents a dialog where a completely different value (Macintosh-#.local) is stored. – Jared Oberhaus Jun 12 '09 at 17:52
@Jared - Sorry I should have made that more clear. Edited the answer. – Chealion Jun 12 '09 at 18:31

System Preferences - Sharing - Computer Name

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Did you try pressing the Edit... button underneath it? Occasionally the Computer Name and Hostname don't match requiring you to adjust it there as well. – Chealion Jun 11 '09 at 23:57
@sweimann, you are almost there. The Edit button next to Computer Name is misleading--it's for editing the local name, not the Computer Name. – Jared Oberhaus Jun 12 '09 at 17:52

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