How to get back or remove purgeable space.

All the other answers I read above were bogus. Finally, I found this article, followed the instructions, and it cured the problem - 85GB of "purgeable" (but unusable apparently) space recovered.

https://www.jackenhack.com/mac-os-purgeable-remove-clear-space/

This is an absolute never ending nightmare. This is a huge bug that is still present months and months later.

As of 10.13.2 "sudo tmutil disablelocal" doesn't work and generates the following error: "disablelocal: Unrecognized verb.", however "sudo tmutil disable local" returns to the command prompt without any error or other message. Does it work?
It doesn't solve the purgeable problem. The worst thing is that I cannot create a time machine backup that doesn't include all the garbage purgeable space. I have about 40GB of real data but my TM backups want to be 250GB. This is one of the most awful "features" [read: bugs] apple has come up with yet. Hours and hours wasted trying to deal with this with no end in sight.

This is the solution!

https://www.jackenhack.com/mac-os-purgeable-remove-clear-space/

In combination with disabling Automatic Time Machine Back Up. It unbelievable that Apple can have a bug like that. Thank you so much for the insight!!!

Thank you so much @murmurnyc

I'm with you on this! We shouldn't have to resort to the internet or Apple forums to essentially perform a simple task of deleting files from an internal hard drive. Apparently, the system is clever enough to manage the 'space' itself; however, in my case I'm trying to install the pending macOS 10.13.2 update but it says I need another 2.1GB of disk space - Despite deleting and moving over 60GB of files this afternoon?! I have rebooted my MBPr several times, toggled the Backup Time Machine settings, and System Preference iCloud on/off - all to no avail. I've even tried the other 'solution' requiring creating large 'dummy' files to replicate and fool the system?! Give me strength! We never even had these problems in the 1980s FFS!

This is both annoying and frustrating. Give users the choice of how they want files to be managed and ensure both process actually work. Never in all my life of using computers have I been told there's still not enough disk space after properly deleting/moving more than the required space? Utterly ridiculous!

Was this feature dreamt up and employed by some youth in his twenties, straight out of college?

I couldn't agree with you more. It is completely incomprehensible. If you haven' figured it out yet. In the link above you should let the file with the random data creation run until it hits the total size of your disk. Duplicating a 20GB file like the post suggested didn't work for me either as the system was so "smart" (***!!!!). So what I did was let it create a single really large file (which can take over an hour or so to do) but once that large file grew so large that hit the maximum disk size booooom all that 350GB of space I had cleared all of a sudden became available ... Hope this helps.

Thanks for the reply! I tried that process twice. The first time it created a file just short of 6GB then then stopped! I still copied it multiple times but nothing was happening. Suspecting it was an incomplete file I set the limit to 5GB in the commons line and re-ran it & again made multiple copies to the point where I got the error msg before my MacBook effectively froze so I had to power off and back on!

It got to the point where I've just literally came off the Apple support chat msg system. They've asked me to perform the NVRAM reset so I'll try that and see how I get on.

Glad you got yours sorted though!

I believe I’ve resolved this issue; at least in my case.

Just to recap:

I was unable to download and install an Apple update (10.13.2 from 10.13.1) as I was repeatedly told I need to free up 2.1GB despite already having deleted and moved (to an external HDD) over 60GB! 'Get Info' of Macintosh HD showed I had almost 92GB ‘available’ with almost 85GB ‘purgeable’. Rebooting made no difference, and neither did the 'auto backup' in Time Machine or the manage space option under iCloud properties.

Thinking Time Machine Backup was involved somehow I tried to perform a backup (since the last was 7 months ago) but it said the task wasn't able to commence as the disk was being encrypted or decrypted. Since this was a new external HDD with software to create partitions, etc. (one for my BootCamp backups) I suspected I must have selected something on this drive in the past. This MacBook Pro retina is my main Windows 10 device, and my backup device for my 2017 iMac used for Logic Pro. I went back to my previous older HDD used for backups and tried that but received the same message? Strange, since that worked okay in the past. I then checked System Preferences, Security & Privacy, and discovered that the local Macintosh HD itself was being encrypted!! ***!

This must be the issue! The other systems/tasks are unable to do anything until this task is complete. Since I last logged into the Mac partition in December (5 weeks ago) it looks like this process had never completed in the background. I was totally unaware. Why couldn't any error messages make it clear that my Mac was encrypting the local HDD in the background? A fancy little icon at the top right of the screen would also have been nice and helped! Something like a black vault icon and white key inside it, beside the Bluetooth or magnifying glass, for Spotlight Search, for instance?

Anyway, I went to bed (it was 3am!) and waited for the drive to finish encrypting overnight then rebooted it in the morning. voilà! I then had over 90GB available, and only 20MB purgeable! Yes MB, not GB! I then successfully performed a Time Machine backup! Then I downloaded and installed the latest 10.13.2 without issue! Sorted! When Apple Support called me at 11:30 I then happily told him it was resolved!

Unbelievable!

For me, (my longer answer is made in a reply to someone else below) I noticed the following:

I then checked System Preferences, Security & Privacy, FileVault tab, and discovered that the local Macintosh HD itself was being encrypted!!

If so, wait, reboot, check Time Machine Backup, etc. Try a download!

1. No.
2. No.

That is entirely under the control of the OS, not the user. Purgeable space is disk space not in use but not empty. The OS can recover that space if needed because the disk is too full. It does not mean you have anything in that space that is gone or recoverable.

There is information here on the Purgeable section in the storage display.

If you don't have Optimize storage turned on, it can also be Local Snapshots which are created by Time Machine when your laptop is not connected to the backup drive. They can be purged if space is needed, or when you connect back to the backup drive and the backups are merged into the Time Machine backup.

I just realized I didn't post the link to the article.

Here's the short version: What is 'Other' and 'Purgeable' in About This Mac? - Apple Support

And here's more info on freeing up space on your hard drive which talks about the purgeable section a bit: Free up storage space on your Mac - Apple Support

Information only, not an answer. iCloud is a syncing system, not an external storage system.

Thanks Eric, you are 100% correct. I've also moved my issue to my own question.