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I ran a process that was writing stderr log messages to a file and didn't realize how fast the log file would grow. The result is that the log file filled up the entire rest of my hard drive and now when I try to remove the file using rm, the computer freezes. I'm running OS X Mountain Lion and my primary hard drive is 2TB. The log file is consuming over 1TB of disk space.

Do I need to just let rm run for a long time to remove a 1TB file? Should I just restore from a time machine backup?

ewwhite
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RyanH
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2 Answers2

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You want to zero the log file from the command line.

Something like : > /path/to/file.log

See: Is there a way to delete 100GB file on Linux without thrashing IO / load?

Community
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ewwhite
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  • Any explanation for why this would be faster? – Jeff Ferland Sep 20 '12 at 17:38
  • When there's no (other) write access to the file, truncate vs. unlink shouldn't make much of a difference. – Ansgar Wiechers Sep 20 '12 at 20:36
  • I assumed the app was still writing. – ewwhite Sep 20 '12 at 20:41
  • This worked, although there was nothing still writing to the file (because the disk had completely filled up as a result of writing to it). It's not clear to me why this worked and rm did not. – RyanH Sep 20 '12 at 20:44
  • @RyanH Asking that question will only result in disparaging remarks about HFS and the Mac OS kernel's disk-scheduling algorithm (both of which SUCK and cause interactive performance to go to the sad place if you do something disk-intensive) – voretaq7 Sep 20 '12 at 20:47
  • *shrug* Still a mystery, then. – Jeff Ferland Sep 20 '12 at 20:47
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    I'm not sure if this is what was happening in this case, but in general a file's space isn't freed until its last link is removed (e.g. with `rm`) AND the last process that had it open closes it. If the process writing to it still had it open, `rm` won't have recovered the space -- but truncating it (e.g. with `: >`) will, even if it's still open in some other process. – Gordon Davisson Sep 21 '12 at 06:40
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Do I need to just let rm run for a long time to remove a 1TB file?

Yes. It's very likely that a file which filled up the disk is spread into fragments everywhere and the filesystem needs to adjust the free list entries for every single fragment. This takes a while.

Should I just restore from a time machine backup?

This is an option. It's debatable whether it would take longer. If you think you might lose anything, just wait for rm.

Jeff Ferland
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  • I tried letting rm run for more than a day and it didn't finish and the computer was completely unresponsive. The `: > file` approach finished within a few minutes. – RyanH Sep 20 '12 at 20:46