Following on from our guide on creating and disk partitions on macOS, today we’ll cover safely removing them, including in what situations it involves loss of data. This guide uses macOS’s built-in disk management program, Disk Utility.
Before we go any further, remember that manipulating drives, and especially removing partitions, is a process that goes hand in hand with removing the data on them. Check what you’re doing at each stage, and have any critical data backed up first.
1) Launch Disk Utility from /Applications/Utilities, or via Spotlight.
The sidebar on the left shows your connected drives, with their sub-partitions. The main pane to the right shows information about the drive which you currently have selected.
2) Locate the disk which you want to edit in the left-hand sidebar. If you cannot find your drive there, ensure it is working, connected to power, and plugged into a compatible port. Try disconnecting and reconnecting it if necessary. Any drives not appearing in the sidebar cannot be edited by Disk Utility. If the drive you want is greyed out, select it and hit the Mount button in the top bar to continue.
3) Select the disk (not its sub-heading partitions) to be formatted in the sidebar, and make sure its information is shown in the main pane.
Any changes made in the main pane will be applied to the disk selected in the sidebar, so make sure you have the correct one selected before each step.
As you can see from the image in Step 3, I have a Western Digital hard drive which is split into two partitions. I want to remove the second partition on the disk (titled Storage).
4) Click the Partition button in the top bar. A window of options will appear, showing your current partition map.
The disk’s partitions are shown in a pie-chart, going clockwise in terms of physical position on the disk (my first partition is TM, the second is Storage).
5) To remove a partition, first select it by clicking on it in the pie, then click the minus symbol (-) button beneath the pie. Multiple partitions can be removed at a time.
Bear in mind, you can remove as many partitions as you like, but there are some rules governing the process. The first partition on the disk cannot be removed, it can only be resized/reformatted. The very first partition also cannot be deleted as it contains the Partition Scheme, but this partition is not editable/visible in Disk Utility anyway, so don’t worry about it. If you want to change that one, you must reformat the entire disk to a new Partition Scheme, which wipes all partitions on the disk.
Deleting a partition at the end of the disk will normally cause the partition before it to be automatically grown to fit the space it has left, unless you add a replacement partition there instead. However, partitions in file formats other than Mac OS Extended (Journaled) may not be eligible for resizing in this way. If this happens, not only can that partition not be resized, but all partitions after it on the disk cannot be removed either, because the ineligible partition preceding them cannot grow to fill their space. This is easily solved; simply reformat the non-Mac OS Extended (Journaled) partition to an eligible partition first, then remove it and any subsequent partitions that you want rid of.
If you’re working with CoreStorage partitions, they may need to be reverted to simple partitions before certain operations can be performed, though in my experience they do not affect the removal of subsequent partitions on the disk, and can be resized easily too.
Obviously, any partitions which you remove or re-format will be WIPED of their data.
6) Once you’re happy with your new layout, have removed all the partitions you want to, and have resized previous partitions to fill their space or replaced them, hit the Apply button to make your changes.
7) A confirmation will appear, summarising the resizes, removals, and additions.
Read the confirmation carefully to ensure you’re not about to delete a partition you didn’t intend to by mistake, then click Partition.
8) This should finish everything up. After a bit of unmounting and remounting, your drive’s partitions should reappear.
The removal and addition of partitions can be finicky, especially when dealing with logical volumes and different file formats, so if you have a more complex set-up which is not covered here, feel free to ask a question in the comments section and I’ll try to help you out with it.
Let me know if you have any requests for guides you’d like to see us do, or tips, at firstname.lastname@example.org!