MacOS – Missing disk space on macOS

disk-spacemacosstorage

I have a 250G disk on my Mac with around 100G in use. But the system reports only around 20G of free space. I'm using macOS 10.13.2. I have the problem at least since the upgrade to High Sierra, but probably also before.

"About This Mac" –> "Storage" reports that "System" is using around 180G. But if I check the complete disk, it looks like that:

$ sudo du -cxhd 1 /
  0B    /.HFS+ Private Directory Data
1.0K    /home
4.3G    /usr
4.2G    /.Spotlight-V100
1.0K    /net
 34G    /nix
  0B    /.PKInstallSandboxManager
  0B    /.PKInstallSandboxManager-SystemSoftware
2.6M    /bin
  0B    /Network
1.1M    /sbin
3.8G    /Library
  0B    /.Trashes
6.5G    /System
476K    /.fseventsd
du: /private/var/db/ConfigurationProfiles/Store: Operation not permitted
du: /private/var/folders/z7/[...]/0/SafariFamily: Operation not permitted
du: /private/var/folders/z7/[...]/0/com.apple.LaunchServices.dv: Operation not permitted
du: /private/var/folders/z7/[...]/0/com.apple.nsurlsessiond: Operation not permitted
du: /private/var/folders/z7/[...]/0/com.apple.routined: Operation not permitted
du: /private/var/folders/zz/[...]/0/com.apple.nsurlsessiond: Operation not permitted
8.0G    /private
8.6M    /.DocumentRevisions-V100
  0B    /.vol
 32G    /Users
 11G    /Applications
207M    /opt
5.0K    /dev
4.0K    /Volumes
  0B    /cores
104G    /
104G    total

df also says that only 20G are available:

$ df -h /
Filesystem     Size   Used  Avail Capacity iused               ifree %iused  Mounted on
/dev/disk1s1  234Gi  211Gi   20Gi    92% 4019132 9223372036850756675    0%   /

Any tool I was using (Finder, Disk Inventory X, etc.) shows more or less the same numbers like df and du.

Output of mount:

$ mount
/dev/disk1s1 on / (apfs, local, journaled)
devfs on /dev (devfs, local, nobrowse)
/dev/disk1s4 on /private/var/vm (apfs, local, noexec, journaled, noatime, nobrowse)
map -hosts on /net (autofs, nosuid, automounted, nobrowse)
map auto_home on /home (autofs, automounted, nobrowse)

I read and tested many, many things like:

… but with no success. So what could consume more than 100G of disk space without showing up in any tool?

Update

Running „First Aid“ in recovery mode:
first aid

What does this error message mean?

error: btn:1: invalid key order (1) oid 440198 / oxid 114577
fsroot tree is invalid.

Update 2018-01-25

Another report of the same error: https://discussions.apple.com/thread/8246182 (but no answers, yet)

I'm pretty sure this file system error is the root cause for the missing disk space. But I have no idea how to fix that. I was hoping that 10.13.3 would maybe solve it, but it didn't change anything. I guess I need to reinstall…

Best Answer

It seems like the two most likely candidates are a mounted (shared) disk overwriting a location with large files, hiding them from your view, or large (or many many small) files that are held open by a process, but have already been deleted. If you haven't rebooted the computer yet, that's worth a shot, but also booting into recovery mode and running first aid on the disk might help. lsof | grep deleted might also reveal interesting information, if lsof is available on OSX (I assume it is, but I've never looked)

I've also noticed in my own use that if I use a tool like DiskInventory or Grand Perspective and there are other users on the system, they won't show the size of other users files if I don't have read access to them (reasonably so). If you have other users on your system, they may have large files in their home directory you're not seeing.

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