Preserve rustup-managed files in Ubuntu runner images

.github/workflows/build-docker-images.yml

@@ -129,6 +129,15 @@ jobs:
             NODE24_ARCH_RELEASE=${{ env.NODE24_ARCH_RELEASE }}
             ${{ matrix.IMAGE.BUILD_ARGS }}
           outputs: ${{ ((github.event_name == 'push' || github.event_name == 'schedule' || github.event_name == 'workflow_dispatch') && github.ref == 'refs/heads/main') && 'type=registry,compression=zstd' || 'type=docker' }}
+      - name: Check Rust component manifests
+        if: matrix.IMAGE.DOCKERFILE_PATH == 'runners/ubuntu'
+        run: |
+          # Exercise the uninstall path even if stable has not changed since
+          # the image was built. This container is disposable.
+          docker run --rm \
+            --pull=${{ github.ref == 'refs/heads/main' && github.event_name != 'pull_request' && 'always' || 'never' }} \
+            ghcr.io/pyca/${{ matrix.IMAGE.TAG_NAME }} \
+            rustup component remove cargo llvm-tools-preview rustc rust-std
       - uses: actions/attest-build-provenance@4d101475d8b20a2381f78447822ac1eab6504dd8  # v4.2.2
         with:
           subject-name: "ghcr.io/pyca/${{ steps.image-name.outputs.ATTEST_IMAGE }}"

runners/ubuntu/Dockerfile

@@ -10,6 +10,10 @@ ENV DEBIAN_FRONTEND=noninteractive
 # "ANSI_X3.4-1968".
 ENV LANG=C.UTF-8
 
+# Docker overlay filesystems can reject directory renames during toolchain
+# updates with EXDEV. Allow rustup to copy the files in that case.
+ENV RUSTUP_PERMIT_COPY_RENAME=1
+
 # Don't unpack things nothing in CI uses: static libpython and OpenSSL, gcc's
 # LTO backend, and the sanitizer runtimes (hard deps of libgcc-dev).
 RUN printf '%s\n' \
@@ -64,13 +68,13 @@ RUN if [ "$(readelf -h /proc/self/exe | grep -o 'Machine:.* ARM')" ]; \
 
 RUN python3 -m venv /venv && /venv/bin/pip install -U pip wheel --no-cache-dir
 
-# We only need llvm-profdata and llvm-cov from llvm-tools-preview (for rust
-# coverage). Its libLLVM.so is identical to rustc's, so symlink it, then strip
-# the big binaries (with llvm-strip; GNU strip breaks them) and drop the rest.
+# Deduplicate libLLVM and strip the big binaries (with llvm-strip; GNU strip
+# breaks them). Keep all files recorded in rustup's component manifests:
+# deleting even unused files prevents rustup from uninstalling or updating
+# the toolchain.
 RUN curl -sSf https://sh.rustup.rs -o /tmp/rustup-init.sh && \
     sh /tmp/rustup-init.sh -y --default-toolchain stable --profile minimal --component llvm-tools-preview && \
     rm /tmp/rustup-init.sh && \
-    rm -rf /root/.rustup/toolchains/*/share/doc /root/.rustup/toolchains/*/share/man && \
     sysroot="$(/root/.cargo/bin/rustc --print sysroot)" && \
     host="$(/root/.cargo/bin/rustc -vV | sed -n 's/^host: //p')" && \
     cd "$sysroot/lib/rustlib/$host" && \
@@ -84,9 +88,5 @@ RUN curl -sSf https://sh.rustup.rs -o /tmp/rustup-init.sh && \
              /root/.cargo/bin/rustup \
              bin/rust-lld bin/llvm-cov bin/llvm-profdata; do \
         if [ -f "$f" ]; then bin/llvm-strip --strip-all "$f"; fi; \
-    done && \
-    for f in $(sed -n "s|^file:lib/rustlib/$host/bin/||p" "$sysroot/lib/rustlib/manifest-llvm-tools-preview-$host"); do \
-        case "$f" in llvm-cov|llvm-profdata) ;; *) rm "bin/$f" ;; esac; \
-    done && \
-    rm -f lib/librustc-stable_rt.*.a bin/wasm-component-ld
+    done
 ENV PATH="/root/.cargo/bin:$PATH"