I have Docker 24.0.4 on Centos 7. I have tried to generate some big multiplatform images and now I have 10 GB of wasted space that I don't know how to reclaim.
Following this tutorial I have executed
docker buildx create --use --name buildx_instance
then I built some images (docker buildx build --platform linux/amd64,linux/arm64 ...) and finally I tried to clean everything with:
docker buildx stop buildx_instance
docker buildx rm buildx_instance
docker buildx prune
docker system prune
But I noticed that 10 GB are still missing, so I examined Docker's folders with ncdu and I found some big subfolders of docker/vfs/dir that clearly contain files of the images I have just built with buildx.
The tutorial says that images created with buildx
won't be visible under
docker imagesand these images will be in buildx cache only
so how can I delete them? I don't want to use a brute force approach (stop/delete/reinstall everything). And how can I associate each subfolder of docker/vfs/dir to the right image?
Note also that I don't know why my Docker is using vfs instead of overlay2; I discovered it searching for the wasted space. The file /etc/docker/daemon.json contains only
{
"data-root": "/docker"
}
because /var is in a very small filesystem.
I have another Centos 7 machine with Docker 23.0.6 without /etc/docker/daemon.json: it has the overlay2 folder instead of vfs. I used buildx on this machine too, in the same way, and I don't see wasted space. Why? What's the difference?
I already tried docker system prune, now I have tried also docker system prune -a and it solved my problem.
It deleted all not-running images (expected and unwanted but acceptable) and some "build cache objects" then said:
Total reclaimed space: 4.332GB
but the difference reported by df -h is 13 GB and the folders that I wanted to remove are gone.