Rancher Desktop's disk only grows: diffdisk, image pruning, and getting space back to macOS

Rancher Desktop runs containers inside a small Linux virtual machine, and that machine's disk is a single file: ~/Library/Application Support/rancher-desktop/lima/0/diffdisk. Images, containers, volumes and build cache all live inside it. Deleting an image frees space inside the file, but not on your Mac.

Read the real size

The disk is a sparse file. Finder and ls show the size it is allowed to grow to. du shows what it actually occupies.

cd ~/Library/Application\ Support/rancher-desktop/lima/0
ls -lh diffdisk     # the maximum
du -h diffdisk      # what it really uses

Step 1: prune inside the machine

Use the client that matches your container engine, chosen in Rancher Desktop's preferences.

# dockerd (moby) engine
docker system df
docker system prune -a          # unused images, stopped containers, networks
docker builder prune -a         # build cache

# containerd engine
nerdctl system prune -a

Add --volumes only when you are sure no volume holds data you need, such as a local database.

Step 2: hand the freed space back to macOS

After pruning, the space is free inside the machine but still allocated in the file. Trimming tells the virtual disk which blocks are unused.

rdctl shell sudo fstrim -av
du -h ~/Library/Application\ Support/rancher-desktop/lima/0/diffdisk

Step 3: the logs

A Rancher Desktop issue on GitHub reported a single network log file growing to hundreds of gigabytes. Check the log folders occasionally:

du -sh ~/Library/Logs/rancher-desktop ~/Library/Application\ Support/rancher-desktop/lima/_networks 2>/dev/null

The reset

Troubleshooting, Factory Reset in Rancher Desktop removes the machine and everything in it. It is the quickest way to the smallest disk, and the most thorough way to lose a local database. Export what you need first.

If you also run Docker Desktop, Colima or OrbStack, each has its own disk. See Docker taking up disk space, Colima and local Kubernetes clusters.