Is it possible to split a partition without reformatting the entire disk?

[HandyMac]

I have a 500GB disk in a MacBook that's divided into 6 partitions. I'd like to erase one partition and divide it (only) further into two or three. I don't want to modify any of the other partitions. When I look at the disk in Disk Utility (running from an external drive) it shows I can erase the partition, but not split it. Is there any way to split this one partition into several without having repartition the entire disk (which would require backing up all the other five, then restoring them – lengthy and laborious)?

 

[chscag]

Just coming from Windows? I'm not poking fun here, but why all the partitions? macOS runs much better when you're not manipulating all those partitions. And to answer your question, I don't believe you can split it without disturbing the other partitions.

 

[IHelpId10t5]

I have a 500GB disk in a MacBook that's divided into 6 partitions. I'd like to erase one partition and divide it (only) further into two or three. I don't want to modify any of the other partitions. When I look at the disk in Disk Utility (running from an external drive) it shows I can erase the partition, but not split it. Is there any way to split this one partition into several without having repartition the entire disk (which would require backing up all the other five, then restoring them – lengthy and laborious)?

You may be thinking about this in the wrong way. It may be as simple as shrinking the size of your existing partition (can be done non destructively in DiskUtility) and then creating additional partitions in the available space. I say "may" because Apple has been continually ruining the usefulness of DiskUtility since before Sierra and I have not had the need to do anything like this lately.

 

[HandyMac]

chscag:

Just coming from Windows? I'm not poking fun here, but why all the partitions? macOS runs much better when you're not manipulating all those partitions.

No, in fact I've never used Windows. I got my first computer, a Mac Plus, in 1988, and have been in the Macintosh environment exclusively since then. Made my living for 15 years doing Mac support, but had to stop that work 8-9 years ago due to chronic illness dulling my mind (it's called "cognitive impairment") such that I just couldn't think hard enough to work with computers, which requires a lot of mental energy. However, I got in the habit of maintaining software setups in most versions of Mac OS, as I had to work on Macs of various vintages; and though I haven't been working on others' Macs for some years, I've still found it useful to be able to boot into various old setups occasionally for one reason or another. My primary everyday computer is a 2013 MacBook Pro running Sierra; the MacBook is my backup computer, with a large partition for miscellaneous software (including installers for all versions of OS X), and smaller partitions with versions from 10.6 thru 10.11. (I also have a PowerBook G3 "Pismo" with 10.3 and 9.2, where I've been doing graphic work in PageMaker occasionally until only a few years ago.)

Presently, as my health is improving some, I'm beginning to follow up on a long interest in Linux, and would like to install a couple versions on the MacBook to play with; so I've erased one of the older versions of Mac OS that I'm unlikely to need, and would like to divide the 50GB volume into two to install two versions of Linux. Thus my question.

And to answer your question, I don't believe you can split it without disturbing the other partitions.

Yeah, I figured as much, but thought I'd ask around.

IHelpId10t5:

You may be thinking about this in the wrong way. It may be as simple as shrinking the size of your existing partition (can be done non destructively in DiskUtility) and then creating additional partitions in the available space. I say "may" because Apple has been continually ruining the usefulness of DiskUtility since before Sierra and I have not had the need to do anything like this lately.

Yeah, seems to me I remember doing that shrinking thing in Disk Utility some years back, but I don't see that capability in the El Capitan version. Have to take another, deeper look. I can boot the MacBook in 10.6, see if that can do it. Thanks for the suggestion.

 

[chscag]

Hey... thanks for the explanation. Makes sense. And the previous responder is correct, Disk Utility has been kind of dumbed down to where it no longer does easily what it used to do. Just as a suggestion though.... booting into older setups can be done with external hard drives formatted and fitted with various versions of macOS. Albeit, it will be slower than having everything on the internal hard drive but it might be more manageable.

 

[Fishrrman]

OP:

There used to be an application named "iPartition" that could do this.
I've used it, and it works well. It takes a little time, but gets the job done.

Be sure you backup first.

 

[HandyMac]

Well, I figured it out. Turned out to be simple enough:

1. Open Disk Utility.

2. Select the disk where you want to create a new partition and click Partition.

3. Select an existing partition in the Volume Scheme list, and click Add (+). Disk Utility splits the partition into two, leaving the data from that partition in one of the new partitions. If the partition is less than half-full, Disk Utility creates two partitions of equal size. Otherwise, it creates one partition large enough for the data, and another partition with the remaining space.

4. Resize the partitions as needed. You can drag the dividers between the partitions in the Volume Scheme list, or you can select a partition in the Volume Scheme list, and then enter a value in the Size field.

5. Choose how to format the partitions that will be erased or created. For each new partition, select it, enter a name, and then choose a format.

6. Click Apply.

Works like a charm, in Snow Leopard as well as Sierra (GUI differs, but procedure is the same). Shrinking the partition is also possible, but for some reason I couldn't shrink the 50GB partition down further than 39GB, leaving only 11GB for the new partition. Whereas the method above simply divided it in half.

It's right there in Disk Utility Help (or in a couple Apple Support documents found by search). Shoulda spent just a little more time researching before crying for help. Duh….