Mac Resize Partition Without Erasing Using Disk Utility

By Vernon Roderick, Last updated: November 19, 2019

You have several partitions located on your hard drive, and you now need to acquire one partition that is bigger than the other. After all, being able to manage more data is without a doubt the dream of many users.

For that, you will have to learn how to do a Mac resize partition without erasing. Fortunately, Apple made it easier to do so. This can be done with the Disk Utility tool on your Mac, but of course, there’s more to it than that.

Although there are testimonies of success around the internet, doing a Mac resize partition without erasing involves not only shrinking the partition but also enlarging it. Either way, with the right conditions, you will be able to do it without any problems. And that’s why we must first discuss the conditions or requirements for doing a Mac resize partition without erasing.

Part 1:Conditions for A Mac Resize Partition Without ErasingPart 2:What to Do Before Mac Resize Partition Without ErasingPart 3:Mac Resize Partition Without ErasingPart 4:Mac Resize Partition with Deleted VolumePart 5:Recover Data from Resized PartitionPart 6:Conclusion

Part 1:Conditions for A Mac Resize Partition Without Erasing

We said “requirements” or “conditions”, but this is actually known to professionals as the “rules of partition Part 1:n resizing”. This is because it’s not necessarily required nor is it something that is doable, but you will have to remember them if you want to get the best results for it.

Regardless, here are the rules that you will need to remember:

  1. Storage space that belonged to a deleted partition will be added to the previous partition. So to increase the space of a partition, you will have to delete the partition next to it.
  2. It is not possible to increase the storage space of the last partition but can be deleted.
  3. To resize a fusion drive, one must update their Mac Utility Disk to the version appropriate to the fusion drive, otherwise, it won’t work properly.
  4. Resizing may require you to delete some of your partition, emphasizing the need for a backup.
  5. Relying on pie chart dividers to resize your volume can be very hard to accomplish.

It is important to understand how this works in order to do tasks related to it successfully. After all, just by the looks of it, these rules can definitely be used to help you towards doing a Mac resize partition without erasing.

Now with those rules out of your way, it might be time to proceed with the actual steps. However, we will first discuss the preparations, since preparing can also be considered as part of doing the task.
Mac Resize Partition Without Erasing

Part 2:What to Do Before Mac Resize Partition Without Erasing

As we’ve said before, there are many users that became successful in their tasks to do a Mac resize partition without erasing. Nonetheless, some of them realized that there are a few things they needed to do first.

The common thing about them is that they’ve encountered some problems due to not realizing this sooner. So to avoid that from happening to you, let’s first discuss the preparation for this. Here are some of the few tricks that you have to learn before doing a Mac resize partition without erasing:

Switch the Disk Utility to Debug Mode

One of the main problems of users is that instead of being able to configure partitions in the Disk Utility, they see it as greyed out or locked out. This is mainly due to the user having inactive partitions.

To fix this, you have to follow these steps:

  1. Open the Terminal.
  2. Type in: defaults write com.apple.DiskUtility DUDebugMenuEnabled 1
  3. Wait for the command to process throughout your Mac.

This should allow you to configure your partitions the way you want. Now let’s head to the second thing you need to do before resizing partitions.

Boot Mac in Recovery Mode

Sometimes, the reason why users encountered errors when resizing partitions is that the partition wasn’t actually a normal partition. There are many types of volumes so this is common.

To turn an otherwise normal partition to the recommended type to do a Mac resize partition without erasing, you have to follow these steps:

  1. Reboot your Mac.
  2. While on the booting screen, hold down Command + R on your keyboard.
  3. Open the Terminal in the window that you’ll get.
  4. Type in: diskutil cs list and press Enter.
  5. Look for the ID of the volume that you want to resize and remember the ID.
  6. Now type in: diskutil cs revert [Volume ID]

This should revert that volume into a normal partition. After this, you won’t have to deal with trouble when resizing that particular partition. Now there is still one step left for the preparation stage.
Mac Resize Partition Without Erasing Using Disk Utility

Mount the Hard Drive

Since hard drives are sometimes not mounted automatically in Recovery Mode, you will have to mound them manually. In addition, in order to do a Mac resize partition without erasing, or any other configuration at that matter, the hard drive should be mounted.

So here’s how you can do this:

  1. While on Recovery Mode, go to Utilities.
  2. Open the Disk Utility from this window.
  3. Right-click on the hard drive that you want to mount, then select the Mount

This should mount the hard drive, which would allow you to configure it as much as you like. During these three steps, it is natural to lose some files. For that reason, we recommend to make backing up your Mac the first thing you do.

Regardless, you should now be fully prepared to do a Mac resize partition without erasing.

Part 3:Mac Resize Partition Without Erasing

To do a Mac resize partition without erasing, there are many obstacles that you will have to overcome. Perhaps one of the most troublesome problems might be the fact that you will have to have a certain amount of know-how to accomplish this.

For this, we will use the Disk Utility tool. The Disk Utility is a tool that allows users to configure their storage disks in several ways. This includes shrinking and enlarging, or in short, resizing partitions. The best thing about this is that you don’t carry the risk of erasing a disk. Thus, it’s the perfect method to do a Mac resize partition without erasing.

Under the right circumstances, you can make it possible. Just follow these steps carefully:

  1. Launch the Disk Utility on your Mac menu.
  2. On the right, locate the drive with the volumes you want to resize. Let’s make them two volumes named A and B.
  3. Now select the Partition
  4. Click on the B volume located on the pie chart.

Disk Utility has a feature that allows you to decrease the size of a certain volume as long as the files that are contained within it will still be able to fit on the new size that you set.

  1. To do this, click on the volume and enter the size on the appropriate field.

For example, you can select B volume. If the current size is 100 GB and the used space is 25 GB, you can enter at least 25 GB on the Size field. Additionally, if you want to resize it into 60 GB, you need to enter 40 GB to the Size field since 100 GB with 40 GB deducted results to the 60 GB volume you desire.

Once you enter the size, press Enter. The pie chart will serve as a visual aid to what you did to the volume. Click on Apply to finish the resizing process. Now the next step is to transfer the leftover space to a third volume so that you won’t lose the data from the B volume. We can name the third volume as C.

  1. Now go back to Disk Utility then select the third volume, the C
  2. Now head to the Edit menu then select Restore.
  3. The Restore window should appear. Move the contents of the second volume B to the third volume C, then click on Restore.
  4. Now click Done.
  5. Go back to the Disk Utility again then select the B
  6. Click on Partition.
  7. Click on the minus icon located at the bottom of the pie chart.
  8. The B volume will be removed finally. You won’t be losing files since the size is now transferred to a new volume, which we named C.

There are many ways to resize a partition, but you will have to put extra effort if you want to avoid losing files from doing so. This is perhaps the only method to do a Mac resize partition without erasing. With that matter settled, let’s head to a simpler solution that carries more risks.
Mac Resize Partition with Deleted Volume

Part 4:Mac Resize Partition with Deleted Volume

Compared to how you can do a Mac resize partition without erasing, not worrying about deleting a volume would, of course, be much easier. To accomplish this, you will still have to make use of the Mac Disk Utility.

The only difference between the two is that you will have to follow a few more steps in the previous section to compensate for the bonus of not having to delete a volume. So you can expect that this would be much easier.

Without further ado, here are the steps you need to follow:

  1. Go to your menu and open the Disk Utility
  2. On the left side of the Disk Utility window, select the drive that you want to resize.
  3. Select the Partition option on your toolbar.

Now there should be a new window appearing with a pie chart and some information about both the device and partition.

  1. Now select the volume that you want to resize.
  2. To enlarge that volume, delete the partition next to it just like we discussed in earlier sections. To do this, click on the minus icon found below the pie chart.
  3. Now click on Apply for confirmation, or Cancel to go back on your command.
  4. This will add the storage space from the deleted partition to the previous volume.

This, of course, won’t allow you to customize how much size you want to add or deduct.

  1. To do that, you will have to select the volume, then hit the Return/Revert option instead of deleting a volume instantly.
  2. Then create a new volume. After this, you will be taken to a pie chart indicating the size of the volume.
  3. Adjust the pie chart so that it specifies the size that you want.
  4. Click on Apply once you are satisfied with the size.

With this, you will be able to resize a partition. Unfortunately, though, you will have to delete partitions to accomplish this. Of course, files contained within them will be deleted as well. It’s tragic, but what if you can recover the files that were deleted along the partitions?

Part 5:Recover Data from Resized Partition

The internet offers a lot of things. A way to completely control your computer, a tool for transferring files, and most importantly, a way to recover your files. Unfortunately, most of the data recovery tools out there are not exactly capable of recovering data from a resized partition.

That’s why we recommend FoneDog Data Recovery software. This is mainly because the software is capable of recovering data from all kinds of sources. This includes the Recycle Bin, a hard drive, memory cards, flash drives, and of course, partitions.

With this, you’ll be able to do a Mac resize partition without erasing without worrying about the risks of losing files, since you can recover it anytime with FoneDog Data Recovery.

Part 6:Conclusion

As you may have already realized, resizing a partition relies on many factors. For one, you will have to set your Disk Utility tool to the appropriate version. There’s also the data loss issue that you need to worry about.

Fortunately, with what we discussed earlier, you won’t have to worry about much. You simply have to follow the steps and you’ll be done. If you find this tutorial on how to do a Mac resize partition without erasing helpful, feel free to share this with others.

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Vernon Roderick

Technical Expertise for PC / YouTube Scriptwriting /Website Optimization

One of my passion is to develop software of my own

I write articles to share knowledge about IT technology and some experience in developing my own software, and developing my own software is one of my passions for work.

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