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Space Consumers - VMs and Containers

May 18, 20262 min read

Space Consumers — VMs and Containers

Docker Desktop

Docker Desktop stores its Linux VM’s entire virtual disk as a single file:

~/Library/Containers/com.docker.docker/Data/vms/0/data/Docker.raw

This is an APFS sparse file. This is crucial:

  • ls -lh Docker.raw shows the logical (maximum allocated) size — e.g., 60 GB
  • du -sh Docker.raw shows the physical (actually written) size — e.g., 15 GB

After docker system prune -a --volumes, the physically written blocks shrink, but the logical size stays the same until the sparse file is compacted. The OS will gradually reclaim the sparse extents, or you can force it:

# The official way to compact Docker.raw
# Requires Docker Desktop to be running (uses its internal VM)
docker run --privileged --pid=host docker/desktop-reclaim-space

Colima / Lima

If you use Colima (a Docker Desktop alternative that wraps Lima, a Linux VM manager for macOS):

# Lima VM disk images
~/.lima/<vm-name>/diffdisk    # the writable overlay disk
 
# Colima (which wraps Lima)
~/.colima/<profile>/
 
# Check sizes
du -sh ~/.lima/
du -sh ~/.colima/ 2>/dev/null

Same sparse file caveat applies — du is the right tool, not ls.

Nix

The Nix store on macOS (installed via the Determinate Systems installer or the official installer) lives at /nix/store/ on a dedicated APFS volume named “Nix Store”. This is critically important for disk accounting:

  • /nix/store/ is on a separate APFS volume, not the Data volume
  • du -shx /System/Volumes/Data will not count it — it’s on a different volume
  • DaisyDisk will not scan it unless it explicitly mounts the volume
  • It will appear as “hidden” or “other volumes” in most disk scanners
# Check if a Nix volume exists
diskutil apfs list | grep -i nix
 
# Check its size
df -h /nix
du -sh /nix/store/
 
# Collect garbage (remove packages not referenced by any profile/generation)
nix-collect-garbage -d
 
# The -d flag removes old profile generations first, then GCs
# Without -d, it only GCs unreferenced store paths (safer)

A multi-year Nix installation with multiple profiles and generations easily reaches 40–100 GB.

Virtual machines (Parallels, UTM, VMware)

ToolDefault disk image location
Parallels~/Parallels/<VM name>.pvm/
UTM~/Library/Containers/com.utmapp.UTM/Data/Documents/
VMware Fusion~/Virtual Machines/<VM name>.vmwarevm/

All of these are sparse files or packages of sparse files. Use du -sh not ls -lh.

See also

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