macOS high sierra system files taking too much space

This just happened! This is not normal. High Sierra has a bug. I've watched my HD space and have had plenty. And now suddenly I have none and 'system' has taken 120GB. This is ridiculous.

Then that is correct. You only have 6GBs of free space. It isn't the operating system which uses around 32GBs. The rest is used by files put in your Home folder.

How to Free Up Space on The Hard Drive

1. You can remove data from your Home folder except for the /Home/Library/ folder.
2. Visit The XLab FAQs and read the FAQ on freeing up space on your hard drive.
3. Also, see Freeing space on your Mac OS X startup disk.
4. Free up storage space on your Mac.
5. See Where did my Disk Space go?.
6. Be sure to Empty the Trash to recover the space.
7. Replace the drive with a larger one. Check out OWC for drives, tutorials, and toolkits.
8. Use OmniDiskSweeper or GrandPerspective to search your drive for large files and where they are located.

Get Correct Storage Information

Do not use the information from the Storage section of the About This Mac dialog. Ignore the Storage information as it is typically wrong. To find out the correct information for any disk: Select a Desktop disk icon. Press Command-I to open the Get Info window and look at the topmost panel displayed. You will find the disk information displayed for Capacity, Available, and Used. If you have more than one disk/partition then repeat for each one on your Desktop.

I ran into the same situation as most everyone here. After I installed the 10.13.4 update. The install went sort of odd. It actually froze up about a third the way through. I had to restart the iMac. Once I did that it completed the install but it took a good long while to do so. Once it was complete, I noticed I went from 1.92TB of free space to 99GB of free space. DaisyDisk showed it as a hidden items in the Library. I tried using Terminal and checking TimeCapsule date stamps like many suggested was the problem. However that was not it. With more digging into the Library folder with DaisyDisk, I discovered the Application Support folder was huge! Further in, I found it was the Adobe preference.dat file. It was 1.89TB in size! Not sure why that was. AND I discovered I had a huge number of old files from past versions of Adobe Software — I thought the uninstall removed all that junk?

So. I found the file. Deleted it. Immediately recovered all my free space. All my Adobe software works fine. So, who knows what just happened. But for me, it was the Adobe prefs.dat file that was the issue.

Hope this helps.

In my research, this isn't the first time something like this happened with the MacOS. I am not knowledgeable enough to know WHAT causes it to happen. However, with DaisyDisk I was able to find the overloaded files. For me, it happened to be the Adobe preference.dat file — it bloomed up to 1.89TB in size. I did a back up of my drive. Then, I deleted the Adobe file. Everything has been fine since.

Now, I will say after installing the High Sierra upgrade. I noticed somewhere in the process it took a really long time — longer than usual with the progress bar during the first start up. Over an hour! I gulped and then did a hard boot with the power button. It then launched fine. And then I saw the HD space was completely gone.

That's my experience with it. Hope this helps.

I have found my solution at macroumors forums! I had operation system taking up 175GB and now takes up only 26.46GM.

Check this out: https://diskwave.barthe.ph/

I hope it works for you also.