How do I clear the purgeable area on my disk?

Question

I cleared space on my disk by deleting files and emptying trash. But, I am unable to make use of the space that I freed up. That is, as you can see the disk reports 142 GB as Available with 83 GB of that as purgeable.

So I should have plenty of space to to copy over a 70 GB file onto the disk. Yet when I try I get an error stating "Not enough disk space to copy", like the following image shows:

How do I clear out the purgeable space to make it truly available for use?

I've tried rebooting in the hopes that a restart clears out the purgeable area, but had no change trying that.

Answer 1

Another option to flush purgeable disk space is to manually create empty disk images, either from Disk Utility (with Cmd+N) or from the terminal, like this:

$ hdiutil create -size 25g empty.dmg
created: /Users/enekoalonso/empty.dmg

This command takes a few seconds, using the default image parameters.

As a note, we cannot create an image larger than the free space available, but using a value close to that will trigger macOS to release a good amount of purgeable space.

This process can easily be repeated as needed, until almost all purgeable space has been released.

Answer 2

You can create a huge file that will force macOS to clean purgeable files to free you space. Do do so, type this command in a terminal:

dd if=/dev/zero of=~/hugefile bs=15m

It will create a file called hugefile in your home folder, which you can check the size with Get Info and stop when it's big enough for you, using ControlC. Or you can simply let it run until you are out of space in the disk and things start to stop working.

This command takes a long time to allocate the memory, you can also stop it when it's 5~10GB and duplicate the file CommandD to create copies and speed up the process.

Then, you just need to delete the files, obviously.

In your case, you already have the file you want to copy, so you could split it into 50 GB chunks and copy one chunk over. Then let the system purge files and repeat. Once you have all the data over, you can combine them - adding the second file to the first, deleting the second file, etc...

• How to merge files after using split command from terminal?

The main problem is that “purgeable” space is not one monolithic item - it is potentially local time machine or filesystem snapshots, cached data, derived data, iCloud photos at full resolution that will be downsampled as you start to get closer to no free space available.

The system will self correct if you can bring the data over in two pieces in your case, or in n-pieces in the general case.

Answer 3

If time machine is the taking the space, than using tmutil can help. List of snapshots can be checked using:

tmutil listlocalsnapshots /

And cleanup upto 100GiB using:

tmutil thinlocalsnapshots / $((100 * 1024 * 1204 * 1024)) 4

Last two arguments are:

• amount of space to try to reclaim (using $(( )) to calculate 100 GiB)
• urgency, 1 is default, 4 is highest (didn't find better description)

There is a mention of tmutil in a comment, but not of thinlocalsnapshots.

Answer 4

I was able to cause the purgeable area to get cleared by copying over temporary smaller files which eventually caused the purgeable space to be cleared. Once the large purgeable area was cleared then I could delete the temporary smaller files and copy the large one that I intended.

Note, that deleting the smaller temporary files caused my purgeable area to grow again, fortunately it grew small enough that I could copy the large file over. Hopefully Apple refines this over time.

Answer 5

There seems to currently be no way of getting a list of what the OS considers purgeable files in order to delete them, but there are some candidates to consider, such as cached files.

This particular file can grow quite large, and once removed reduces the purgeable data size;

/System/Library/Caches/com.apple.coresymbolicationd/data

To get an idea of the size of the file, you can run ls as the sudo user;

sudo ls -la /System/Library/Caches/com.apple.coresymbolicationd/data

A search for the file provides a few links to queries on its size, such as this Q&A here.

Details on the file itself are scarce, but it seems related to symbol lookup for crashed and problematic processes; as is evidence in this linked Q&A, with more information this post. Follow on the Q&A linked above, it does seem safe enough to delete, this file.

Removal of the file would need to be done with sudo, details are provided in the Q&A post. The gist of it is to move (as sudo) the file to somewhere in your home directory (e.g. ~/Documents/SymbolDataDelete), reboot the machine and then delete the file.

Note: the symbol file will be created again, this appears to be normal, but you should be able to better manage the size it consumes if it becomes too large.

Warning: using sudo can be dangerous... use with care.

On the expected results; I don't anticipate that this single file will be the sole contributor to the purgeable data (assuming the cloud drive is off etc.), but it did clean up about 95% of the purgeable data I had.

General observations

It may seem obvious, but a reboot cleans out a lot of the temporary and cached content. Give it a few minutes after the restart. Personal observations have been that after a couple of weeks, a reboot cleans up in the order of a gig of purgeable space...

Answer 6

Final step which worked (using Catalina 10.15.7 on an iMac with an APFS formatted Fusion Drive)

• Confirm that a recent backup is available for the system before proceeding to reduce the risk of losing data.
• Boot to recovery mode and reinstall the Operating System. See How to reinstall macOS from macOS Recovery. Do not erase or format the disk.
• Once the reinstallation was complete, the purgeable storage was substantially smaller and operations which previously failed due to insufficient disk space succeeded.

In this scenario, an iOS device backup to a Mac was failing and it succeeded after the reinstall of the OS.

Other steps taken prior to reinstallation, which might not be required

• Use Disk Utility to run First Aid on the Macintosh HD volume (and the Macintosh HD - Data volume if it is present). See Repair a storage device in Disk Utility on Mac.
• Reset NVRAM. See Reset NVRAM or PRAM on your Mac.
• Create a new Administrator user, log out, then log in with the new user. Attempt the action which failed due to insufficient space. If it fails, it is not likely related to original user account. See Set up users, guests, and groups on Mac.
• Boot to safe mode and attempt the action which failed due to insufficient space. If it fails, it is not likely related to applications or extensions. See How to use safe mode on your Mac.