I am trying to use the Network Link Conditioner preference pane included with the Hardware IO tools in the developer tools to throttle Internet speeds. I can open and load the preference pane, but as soon as I try to turn it on, System Preferences crashes.
Why is this happening and how can I fix it? I have a 13" MacBook Pro with a 2.3 GHz Intel Core i5 running OS 10.7.3.
Here's the log entry for the NLC crash:

5/10/12 9:31:39.150 AM [0x0-0x1c51c5].com.apple.systempreferences: NLCd : Bootstrap failure
  • I have exactly the same symptoms as you :(
    – Andy
    Apr 23, 2012 at 15:35
  • Could be lots of reasons. Did you use Console to check the logs? Meanwhile, since Network Link Conditioner is just a front end for ipfw you can use ipfw directly.
    – Old Pro
    May 10, 2012 at 5:47
  • @OldPro I've updated my question to include the Console log information.
    – daviesgeek
    May 10, 2012 at 16:32
  • You've downloaded the latest Xcode from the MAS?
    – da4
    May 10, 2012 at 16:48
  • @da4 Yes I have.
    – daviesgeek
    May 10, 2012 at 16:48

3 Answers 3


Just a quick note to say that I eventually stopped the crashing by manually copying these two files from another OS X machine and then manually starting the nlcd daemon (if you don't have another Mac, I posted my copies of those files here)

Copied these files:
Run these three commands:

sudo chown root /System/Library/LaunchDaemons/com.apple.NetworkLinkConditioner.plist      
sudo chmod 644 /System/Library/LaunchDaemons/com.apple.NetworkLinkConditioner.plist   
sudo launchctl load /System/Library/LaunchDaemons/com.apple.NetworkLinkConditioner.plist

After that the pref pane didn't unexpectedly exit when moving the switch to 'on'.

Taken from https://devforums.apple.com/message/645980#645980

  • So sorry I didn't see this!! I did try this and it seems to work. However, I need to try it out on a faster network. Give me a few days to test it out. Thanks!
    – daviesgeek
    Jul 13, 2012 at 2:57
  • Seems to work and the bandwidth is being limited, so I accepted your answer. Thanks so much! Now I just wish Apple would get their act together and fix this. Off to submit some Apple feedback!
    – daviesgeek
    Jul 17, 2012 at 17:11
  • Is it possible to share those files on a different server? It seems like we have to signup and the language cannot be set to english...
    – Resh32
    Nov 16, 2012 at 8:10
  • Can you please upload it on another place? I can't download it anymore ... Apr 23, 2013 at 8:36
  • Indeed... that website malware heaven.
    – Michael
    Nov 9, 2013 at 19:22

I filed a bug report (#11891721) for this. I linked to odyth's answer in the report and this is their response.

Changing the nlcd file over to an older version makes it compatible with the preference pane, (as you did in this case). The current version of the prefpane works with the latest nlcd. We can not do anything about the older installs of nlcd or the prefpane that you have.

We are closing this bug since we are aware of the issue.

Please be sure to regularly check the seed notes and release notes for any updates that might affect this issue.  Again, thank you for taking the time to submit bugs. We sincerely appreciate your input.

So there's the official answer.

  • 1
    In other words, i was having the same problem on OS X Lion using the Hardware IO Tools from February 2012. After reading this answer i tried the Hardware IO Tools from Late July 2012 (which is announced for OS X Mountain Lion) and it worked fine. Dec 29, 2013 at 23:06

I had the same issue in Yosemite.

Tried with the files mentioned here, but it was still crashing.

Giving admin rights to my OS X user seemed to "solve" the issue. In other words, running the app as a "Standard" user seems to cause the crash for me.

Still it is not a nice solution, but maybe it helps some people or give insight for a better solution. :)

  • this is still true for macOS Sierra 10.12.3
    – schmidiii
    Mar 28, 2017 at 11:42

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