Mac OS X: About background maintenance tasks

Mac OS X periodically runs background tasks that, in part, remove system files that are no longer needed. These tasks run at certain times if the computer is not in sleep mode. The tasks purge older information from log files or delete certain temporary items.

Learn how the tasks automatically run after the computer wakes in Mac OS X v10.6 and later, and how you can manually force the tasks to run in Mac OS X v10.5 or earlier.


Mac OS X v10.6 and later information

In Mac OS X v10.6 and later, background maintenance tasks that do not run when the computer is asleep are run after it wakes from sleep mode.

For more advanced information, visit these developer webpages:

Mac OS X v10.4 and v10.5

If your computer is shut down or in sleep at the designated times, the maintenance does not occur. In this situation, you may wish to force the maintenance tasks to run. There are two options: Use a third-party application or Terminal.

Use a third-party application

Some third-party applications may allow you to run these tasks whenever you wish. Four examples include:

  • Macaroni by Thomas Harrington
  • Mac Janitor by Brian R. Hill
  • CronMaster by Dan Klein
  • weRclean by Parental Advisory

You can search for these or other solutions at VersionTracker (

Use the Terminal (advanced)

Note: As mentioned above, these steps are not necessary in Mac OS X v10.6 or later.

  1. Open Terminal (/Applications/Utilities).
  2. Type: sudo periodic daily

    Tip: Typing "daily" runs tasks normally scheduled for a daily interval. Type "monthly" or "weekly" in place of "daily" to runs tasks scheduled for those intervals. Weekly tasks usually require a longer time to run than others.
  3. Press Return.
  4. Enter your Admin password when prompted, then press Return.
  5. Quit Terminal when the task is complete.

The tasks are scheduled for 03:15 to 05:30 in your computer's local time zone. This is described further in "Mac OS X: Unexplained Disk Activity Produced by 'find' Process." These tasks do not run if the computer is shut down or in sleep mode. If the tasks do not run, it is possible that certain log files (such as system.log) may become very large in Mac OS X v10.5 or earlier.

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