Permission denied creating tar for Apt files

Based on @joshmgross’s latest comment in https://github.com/actions/cache/issues/133#issuecomment-629381394, here’s my use case, same as @evandrocoan https://github.com/actions/cache/issues/133#issuecomment-602695437…

caching Apt list and package files in Ubuntu

Example workflow

The Apt step here takes about 35 seconds without caching. I’m hoping the cache will improve that. I’m also not 100% sure about the paths because I haven’t been able to test it yet.

      - name: Use Apt lists cache
        uses: actions/cache@v1
        with:
          path: /var/lib/apt/lists
          key: ${{ runner.os }}-apt-lists
      - name: Use Apt packages cache
        uses: actions/cache@v1
        with:
          path: /var/cache/apt
          key: ${{ runner.os }}-apt-packages
      - name: Install Apt dependencies
        run: |
          sudo apt-get update
          sudo apt-get install -y liblua5.1-dev luarocks

Error during post job

Post job cleanup.
/bin/tar -cz -f /home/runner/work/_temp/207e89c2-b0e5-4443-915a-2eafc37bc59b/cache.tgz -C /var/cache/apt .
/bin/tar: ./archives/partial: Cannot open: Permission denied
/bin/tar: ./archives/lock: Cannot open: Permission denied
/bin/tar: Exiting with failure status due to previous errors
[warning]Tar failed with error: The process '/bin/tar' failed with exit code 2

[AJMansfield]

I was able to at least successfully save a cache of the downloaded .deb packages with this step:

      - name: Cache APT packages
        uses: actions/cache@v2
        with:
          path: |
            /var/cache/apt/archives/**.deb
            !/var/cache/apt/archives/partial
            !/var/cache/apt/archives/lock
          key: ${{ runner.os }}-apt

However, when attempting to restore this cache, the attempt to extract these cached files still results in Cannot open: Permission denied errors for each file:

Received 0 of 85361645 (0.0%), 0.0 MBs/sec
Received 71303168 of 85361645 (83.5%), 34.0 MBs/sec
Received 85361645 of 85361645 (100.0%), 35.8 MBs/sec
Cache Size: ~81 MB (85361645 B)
/bin/tar --use-compress-program zstd -d -xf /home/runner/work/_temp/6cb673f4-802b-4627-a69c-fc30b46f495f/cache.tzst -P -C /home/runner/work/haxe/haxe
/bin/tar: ../../../../../var/cache/apt/archives/autopoint_0.19.8.1-6ubuntu0.3_all.deb: Cannot open: Permission denied
/bin/tar: ../../../../../var/cache/apt/archives/bubblewrap_0.2.1-1ubuntu0.1_amd64.deb: Cannot open: Permission denied
 ⋮
 ⋮ (50 more lines omitted)
 ⋮
/bin/tar: ../../../../../var/cache/apt/archives/x11proto-randr-dev_2018.4-4_all.deb: Cannot open: Permission denied
/bin/tar: ../../../../../var/cache/apt/archives/x11proto-xinerama-dev_2018.4-4_all.deb: Cannot open: Permission denied
/bin/tar: Exiting with failure status due to previous errors
Warning: Tar failed with error: The process '/bin/tar' failed with exit code 2

If we could just have an option for running the /bin/tar command as sudo, that would make this tool significantly easier to use for caching system packages (like those installed by apt).

[chris-martin]

I have a workflow that opens a Nix shell. It has a lot of small dependencies, and it takes about 4 minutes to download them from various Nix binary caches. Seems like it would be faster to restore from github’s cache. Is there some reason the restore can’t just run as root?