Unable to reduce 900GB of system data files off computer

Freeing up macOS disk space (often times it is file system snapshots)

https://tidbits.com/2024/03/18/follow-these-steps-to-clear-space-on-your-mac/

https://www.stellarinfo.com/blog/how-to-clear-system-storage-on-mac

Applications -> Utilities -> Terminal # may need to give Terminal “Full Disk Access”

Finding big files as candidates for removal

    sudo du -hx “$HOME” /var/* /opt/* /tmp/* /cores | sort -h  # This will take a few minutes
    tmutil listlocalsnapshots /
    diskutil apfs listSnapshots /

ChatGPT and Codex can generate some huge files in $HOME/.codex

The ‘du’ (disk usage) command will show storage being used in every

folder under your Home Folder and the /var, /opt, /tmp & /cores

folders.

After checking for local APFS snapshots (see below), there is a

reasonable possibility your Home Folder tree is where most of the

storage is being used. You can specify other starting folders.

Time Machine snapshots

tmutil listlocalsnapshots /

Snapshots for volume group containing disk /:

com.apple.TimeMachine.2021-04-01-142742.local

com.apple.TimeMachine.2021-04-01-163342.local

com.apple.TimeMachine.2021-04-01-174425.local

com.apple.TimeMachine.2021-04-01-192243.local

com.apple.TimeMachine.2021-04-01-203820.local

com.apple.TimeMachine.2021-04-01-222814.local

com.apple.TimeMachine.2021-04-01-232930.local

com.apple.TimeMachine.2021-04-02-002823.local

com.apple.TimeMachine.2021-04-02-012748.local

tmutil deletelocalsnapshots 2021-04-01-142742 # deletes 1 snapshot

tmutil deletelocalsnapshots /   # deletes all the snapshots

Also see:

    diskutil apfs listSnapshots /

The Spotlight Index can also become too large.

sudo du -hx /System/Volumes/Data/.*100*  # the period before .*100* is important‼️

Rebuilding the Spotlight Index can reduce the excessive size:

https://support.apple.com/en-us/102321

GUI search apps (may also need “Full Disk Access):

brew install —cask omnidisksweeper
brew install —cask radix 

In the first instance you could run a search in Finder to find large files.

Click on your Mackintosh HD in the LH panel then in the menu bar hit File/Find. You can then click the "+" sign and then find "File Size" in the drop down. If it's not there then click other and find it. Run the search and then sort by size descending. That way you can see where and what the large files are. Come back with more details if you are concerned about what you can delete.

Also - a long shot - make sure you've not got any USB memory images hanging around. In finder click on Mackintosh HD. Then hit shift-cmd-. (that's the shift, command and full-stop/period keys) to show hidden files. Click on Volumes and make sure there aren't any USB memory images there. If there are then delete them. (these files are sometimes left behind if you don't eject USB storage properly)

Download the free version of Storeograph to find what is really taking up disk space. It's probably not what you think.

Storeograph

+1 I also recommend using OmniDiskSweeper instead of the built-it Storage eye-candy.

Vicky0707 wrote:

All documents and my photo library came over almost instantly, which was shocking, I have nearly 13k photos in just family/misc. photos library. I was quite impressed that they loaded so quickly.

They might still be mostly in iCloud. By default, iCloud wants to optimize and keep most data in the could. You have to go into iCloud settings and turn off optimization if you want to make sure to have everything local. I do recommend doing that on at least once device just so you can keep a local backup. iCloud is great for syncing, but it's not a backup.

I will go thru the old Mac again and make sure I didn't forget anything. Thank you for the suggestion, now I have a clean Mac to work with. Happy Camper!

900 GB of system data is still not normal. If you're running the same apps, it could come back. Years ago, it was Time Machine local snapshots that were a common cause of this problem. But in recent years, I don't think I've seen the same cause twice. It's just really random. Some app goes crazy and starts writing data without end. Sometimes it's Apple software. Sometimes it's 3rd party software.

In your case, since you still seemed to have plenty of free space, it wasn't causing any problem. But if you drop down to less than 100 GB free, it will reduce performance. Before 50 GB free, and all kinds of strange problems start happening. To make matters even more complicated, the operating system generally won't tell you how much free storage you have. It tells you "Available", which is (usually) something completely different. This is a really common problem, especially with smaller drives.

Sorry about that but my recommendation still stands.

However, if Vicky is short of cash like me, she can try OmniDiskSweeper.

OmniDiskSweeper

Ultimately, I decided to go with the iCloud route. All I need to do is re-download a couple of apps and upload a backup to restore my Quicken account. I saved all my photography work on a separate external HD, I keep those files separate from family and everyday photos. All documents and my photo library came over almost instantly, which was shocking, I have nearly 13k photos in just family/misc. photos library. I was quite impressed that they loaded so quickly. I will go thru the old Mac again and make sure I didn't forget anything. Thank you for the suggestion, now I have a clean Mac to work with. Happy Camper!

Vicky0707 wrote:

I planned to do a current backup and use it for the new Mac but was afraid I would be unable to it due to my current storage on the old Mac. It seems I need to get rid of some system data files??

Please try the migration.

You may well have issues with halving the storage, independent of the system data.

Or not.

Trying is when that becomes clear.

If your usage is below the new storage, the Time Machine migration might well fit.

System data won’t necessarily show in file-focused reports and such, and can include things like caches and backups. Time Machine without access to its archive storage device can borrow lots of free space, for instance.

etresoft wrote:

The easiest way to setup your user on the new computer is via iCloud. Turn on iCloud Drive. In iCloud, turn on Desktop & Document Folders. Do the same for anything that supports iCloud, like Music or Photos.

If the OP does this then they need to have enough space on iCloud for all that data and also on all the devices they synch with iCloud. Also, in my experience the data rates for iCloud upload and download are measured in kB.

IMHO, if the OP chooses they'd be better doing that either by transferring directly from Mac to Mac over the network or via a USB drive.

Personally I wouldn't put Desktop and Documents in iCloud under any circumstances. I tried it once - it was a pain in the neck and an even bigger pain in the neck to reverse. I'm still seeing artefacts of it many years later.

Don't get me wrong- I think this method of data transfer for setting up a new Mac is a good; I've used it for my two most recent Mac purchases because it only transfers files and leaves most problematic configuration settings on the old machine. I just wouldn't use iCloud to do it.

Thank you for the information. I can't seem to find ANY snapshot backups. Let me explain...I knew I had a storage issue and the only external I had was the one I was using for Time Machine and everything else, it is a 5TB HD. That HD was being taken over by all of the Time Machine backups, so I decided to just completely erase it and reformat it. I plan to use that HD for all of my photography photos, since they are large files. I purchased a new SSD 2TB drive to use for the new Mac and it's Time Machine backups. I was going to do a new Time Machine back on the new SSD drive, but realized that my current storage on old Mac exceeds my new Mac considerably. Going from 2TB on old to 512G on the new mini. That is what started my journey to clear all the junk. I have done just all I can do on my own. I have searched for any Time Machine snapshots and I can't find any. Also, in my settings>storage it does list all of the options I see on other people's examples. See photo.

Yeah, but "system data" includes app caches, app profiles, hung up iso images, iphone and ipad backups if you do them on your Mac, Mail attachments and almost anything in your libraries that aren't files, photos, music or videos.

So far I have deleted app caches, there are no iPhone or iPad back ups. I have deleted all mail attachments. I can't find any Time Machine snapshots. I have not looked at app profiles or "hung up" iso images, I will have to figure those out.

First of all, slow down a bit.

Secondly, "System Data" doesn't exist. You can't believe anything you see on System Settings > Storage, so don't even go there.

It looks like you still have plenty of free storage. So the best course of action is to just ignore that which doesn't exist.

The easiest way to setup your user on the new computer is via iCloud. Turn on iCloud Drive. In iCloud, turn on Desktop & Document Folders. Do the same for anything that supports iCloud, like Music or Photos.

Then, login to your new computer and sign into iCloud. Do the same there. Turn on iCloud everything. Once all of your data has synced, you can start using the new computer full time.

Take some time and go through all the apps that you normally use, or might have ever used. Note (literally - I mean write it down) all the data you have on the old computer. Make sure the same data is available on the new one. There might be a few oddballs that you'll have to transfer manually.

Zurarczurx wrote:

If the OP does this then they need to have enough space on iCloud for all that data

That's true. It's one of those problems that can be solved with $12.99.

also on all the devices they synch with iCloud.

That's false.

Also, in my experience the data rates for iCloud upload and download are measured in kB.

Obviously false, although at times iCloud can be frustratingly slow.

Furthermore, from the provided screenshot, we can see that the OP does have some data in iCloud already. There's probably 20-25 GB of additional data that might, or might not, already be in iCloud. I think that's manageable.

IMHO, if the OP chooses they'd be better doing that either by transferring directly from Mac to Mac over the network or via a USB drive.

There are lots of low-level gotchas with that approach. It was a good idea 15-20 years ago. But today, there are too many unique identifiers that can get duplicated and cause lots of odd problems, sometimes years later.

iCloud is designed for setting up a new device, and it does that job well. Let it do it's job.

Personally I wouldn't put Desktop and Documents in iCloud under any circumstances. I tried it once - it was a pain in the neck and an even bigger pain in the neck to reverse. I'm still seeing artefacts of it many years later.

It's worked well for me for many years.

Don't get me wrong- I think this method of data transfer for setting up a new Mac is a good; I've used it for my two most recent Mac purchases because it only transfers files and leaves most problematic configuration settings on the old machine. I just wouldn't use iCloud to do it.

I'm confused. That "don't get me wrong" is usually a qualifier for some other statement. But then you refer to "this method" and it seems like you are referring to iCloud. Then you say you wouldn't use iCloud. So while I'm not sure what you're saying here, I'm sure you're wrong. iCloud is absolutely a great way to setup a new device.

Re-transfer speeds. Sorry - typo in my post. I just did a test. A 150MByte file uploaded to iCloud at 360kbits/second. That's typical in my experience and has ever been thus. It's not at my end - the same file uploaded to my website at 10Mb/s. I've only got the free iCloud - do paying customers get faster rates?

The "this method" I was referring to is the selective copying of user data when migrating as opposed to a full Time Machine or data migration. I've used it successfully by connecting new Mac to old Mac either via cable or network and just migrating files, photos and music. I didn't have any permissions problems.

The only thing I've got against iCloud (for this application) is the speed. At the transfer rates I typically get it would take ten days just to transfer my photos.

Zurarczurx wrote:

I just did a test. A 150MByte file uploaded to iCloud at 360kbits/second. That's typical in my experience and has ever been thus.

Maybe that's a conversation you need to have with your ISP. I didn't have a 150 MB file handy, so I tried the next largest one - 465.1 MB. It uploaded at 9.9 MB/sec. That was after I had tried an IPSW file. I decided that was a poor test because the file was so large. But while I left it running, it hovered between 80-100 MB/sec. And I don't have particularly fast internet. It's just mid-tier fibre.

It's not at my end - the same file uploaded to my website at 10Mb/s. I've only got the free iCloud - do paying customers get faster rates?

It's probably more of a content delivery network issue. Apple has servers all over the world. A DNS misconfiguration, or a CDN misconfiguration, can cause some people to experience lots of problems while other people don't notice anything.

This site is a great example. It's dead as a doornail for me this morning. I was able to refresh a few times to view a few threads where I've participated that have new content. But this tab was dead. The quote button stopped working and then it was just "We'll be back". So I turned on a VPN (yes, I know, the horror!!!) and it works fine now.

These kinds of problems can be both temporary and long term. I remember a few years ago when I was still interested in betas that I couldn't download them at all unless I used a VPN.

When you upload directly to a known server, you're not dealing with a CDN. I had a similar problem with DreamHost years ago. I could connect via ssh and upload/download with great speed. But HTTP downloads, the type customers would see, were almost dial up speeds.

It's 2026 now. The world is devolving. We'll all be back on BBS speeds before long.

The "this method" I was referring to is the selective copying of user data when migrating as opposed to a full Time Machine or data migration. I've used it successfully by connecting new Mac to old Mac either via cable or network and just migrating files, photos and music.

That's fine. And it's a great way to get documents that might not be in iCloud. But it won't get various settings and app-specific data. That's what iCloud excels at. And if a manual copy does get that data, it gets the data incorrectly and confuses lower-level software like Continuity, which expects each device to be unique. When you copy those unique identifiers, strange things start happening.

(Regarding documents that might not be in iCloud. Never store private or sensitive data in iCloud. It's not that secure. It's still the internet and there's a long list of ways that someone other than the owner can access the data. If a given document being published opening would result in anything more than embarrassment, don't put it in iCloud.)

The only thing I've got against iCloud (for this application) is the speed. At the transfer rates I typically get it would take ten days just to transfer my photos.

It's always possible that the OP might experience a similar problem. If so, then obviously the iCloud solution wouldn't work. But I sincerely think that you're the outlier here. The OP already uses iCloud and has a relatively small amount of other data. And there's a good possibility that this other data is already in iCloud.

There's a good chance the OP can simply sign in to the new computer and experience no problem whatsoever. It sure sounds like they've simply been misinformed by that awful "Storage" display and now they think they have a problem, when they really don't.

definitely iCloud will work for most people to make things easier

also saw this the other day - https://github.com/tw93/mole

BUT of course goes without saying that such tools to be used at your own risk (looks like Dev is OK but tool is new and vibe coded etc)

Ian R. Brown wrote:

Download the free version of Storeograph to find what is really taking up disk space. It's probably not what you think.

Thanks for the plug! But the free version of Storeograph only checks storage speed. The Storage management features require an in-app purchase. But there is a very detailed video advertisement with voice over in case anyone wants more information before buying.

Do you have a Time Machine backup?

Irrespective of System Data use, have you tried using that backup to migrate to your new Mac?

These are system data files that are taking up 900GB+.

When I searched for files of large size I only come up with my photo applications.

I planned to do a current backup and use it for the new Mac but was afraid I would be unable to it due to my current storage on the old Mac. It seems I need to get rid of some system data files??

Ignore my last post - it's incorrect - sorry.