diff --git a/.github/workflows/ci-docker.yml b/.github/workflows/ci-docker.yml
index 1082c941182..acb883afbf1 100644
--- a/.github/workflows/ci-docker.yml
+++ b/.github/workflows/ci-docker.yml
@@ -192,6 +192,16 @@ jobs:
     name: Docker${{ matrix.tag }}
 
     steps:
+      - name: Maximize build space
+        uses: easimon/maximize-build-space@v7
+        with:
+          root-reserve-mb: 30720  # https://github.com/easimon/maximize-build-space#caveats
+          remove-dotnet: 'true'
+          remove-android: 'true'
+          remove-haskell: 'true'
+          remove-codeql: 'true'
+          remove-docker-images: 'true'
+
       - name: Checkout
         uses: actions/checkout@v3
         with:
diff --git a/docker/ubuntu-20.04.dockerfile b/docker/ubuntu-20.04.dockerfile
index 3cb049ac60b..3e88746d800 100644
--- a/docker/ubuntu-20.04.dockerfile
+++ b/docker/ubuntu-20.04.dockerfile
@@ -101,7 +101,7 @@ url="${cmake_prefix}${CMAKE_VERSION}/cmake-${CMAKE_VERSION}-linux-${cmake_arch}.
 echo "cmake url: ${url}"
 wget "$url" --progress=bar:force:noscroll -q --show-progress -O ./cmake.sh
 sh ./cmake.sh --prefix=/usr/local --skip-license
-cmake --version
+rm ./cmake.sh
 _INSTALL_CMAKE
 
 # install cuda