Clearing space on a macOS hard drive

As a tester I'm often hoarding articles, data, VMs and tools on my hard drive.

The hard drives a decade ago where IDE or SATA hard drives. It is easy to find 1 terabyte (1000 gigabyte) hard drives. So I tend to put 1 or 2 terabyte hard drives in my computer.

Today you tend to find computers using SSD hard drives. When they first came out all you could find was 128 gigabyte or 256 gigabyte hard drives. Getting 128 gigabytes was normal because the 256 gigabyte hard drive was often a few hundred dollars more.

As time went on, the cost of SSD drives came down. Now it is common to find 256 gigabyte hard drives and it is a few hundred dollars more for a 512 gigabyte hard drive. Still 256 gigabyte is a LOT smaller than a 1 terabyte hard drive.

Large data sets and VMs for testing different operating systems and browsers would often take up a LOT of space. Add to that all the tools I typically use (development, automation, communication, productivity, etc.) and I quickly find a 256 gigabyte hard drive full.

Recently, I kept finding I would have to backup something on my hard drive and delete it to make room for something on a new project. I kept trying to figure out how to free up more space on my macOS hard drive. I have only a 250 gigabyte flash drive in my laptop and it always seemed to be at 230 gigabytes used.

Recently I read about how backing up your hard drive using Time Machine would create these local backups on your hard drive. The article talked about where the folders with the local backup were and how you could just delete the folder and it would free up a lot of room.

With the latest version of macOS (High Sierra 10.13), it uses APFS. This new file system has a number of advantages around speed, encryption, reliability, etc.. However, new file systems often mean just deleting things from the Terminal or using older hard drive clean up applications, could result in the file system getting a little messed up.

So rather than just delete local Time Machine backups, I would recommend using the tools which come with the operating system. In this case the tool is called tmutil.

If you go to a Terminal and enter tmutil it will give me a list of things it can do. One of those things is listing the local backups. To see them you can use:

tmutil listlocalsnapshots /

This will list the local snapshots on the root hard drive. From the output, you can then delete one or more of the local backups. I deleted all the local backups and found my hard drive went from 230 gigabytes used down to 117 gigabytes used. Essentially, the local backups were taking 113 gigabytes (almost half my hard drive).

To delete a local backup, I'd use:

tmutil deletelocalsnapshots <snapshot_date> 

where <snapshot_date> would be the date of the snapshot. Basically, the output of listlocalsnapshots would be:

com.apple.TimeMachine.<snapshot_date>

where <snapshot_date> is something like 2018-01-14.