Delete Mac partitions without losing data

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In a recent Mac 911 entry I explained how to turn two hard drive partitions into one. And while words are great, sometimes it’s more helpful to see something like this in action. And so was this week’s Macworld video conceived.

Note that in the video I state that you can't partition the drive you've booted from. This is incorrect. You can create an additional partition from the free space the drive holds. It's not cogent to this particular exercise but I regret the error.


I have a smallish hard drive here that I’ll split into two partitions. To do that I select the drive, click on the Partition tab, and choose 2 Partitions from the Partition Layout pop-up menu. To make sure I’ll be able to reclaim one of the partitions later I click on the Options button and ensure that either GUID or Apple Partition Map is selected and click OK. (I always choose GUID partition table as that’s the format that works with today’s Intel-based Macs.)

Now, click on Apply to partition the drive with the understanding that doing so will erase every bit of data on it.

Now we have our two partitions. Through the miracle of time lapse I’ve copied some data onto each partition. I’d now like to convert this drive into a single partition without losing my stuff. How do I do that?

I’ll open my second partition and copy everything on it to the first partition. If it doesn’t fit, I could copy it to another hard drive for later copying.

Now that I’ve done this I select the second partition and click on the minus (–) button to delete it. And off it goes, with all its data (which, again, I’ve backed up). But now I’ve got a hole where the partition used to be.

No problem. Drag the bottom right corner all the way to the bottom of the pane and then click Apply. You once again have a single partition that consumes the entire drive space. And, best of all, you haven’t lost a single file on it.

Now, the fine print. If you delete the top partition you can’t resize the bottom one up. There’s no way to drag it to the top. So, deal only with the bottom partition and then expand the top one.

Want more secrets for making your Mac work better? Check out our tips-and-troubleshooting session at Macworld/iWorld in San Francisco March 27-29.

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