diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index abccc50..c8835a0 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -136,7 +136,9 @@ jobs:
         run: |
           echo "backup moby/buildkit image"
           sudo docker image save -o ${GITHUB_WORKSPACE}/images.tar moby/buildkit
-          echo "Back up /var/lib/docker folder structure and other files"
+          echo "prune docker"
+          sudo docker system prune -a -f
+          echo "back up /var/lib/docker folder structure and other files"
           sudo rsync -aPq /var/lib/docker/ ${GITHUB_WORKSPACE}/docker
 
       - name: Maximize build space