docker-layer-extract

docker-layer-extract

Tool to extract individual layers from a saved docker image

Building the binary

• Using local go installation:

  $ GOBIN=$PWD go install github.com/micahyoung/docker-layer-extract@latest
  

• or alternatively, using Docker:

  $ docker run --rm -v $PWD:/out -e GOOS=$(uname -s|tr 'A-Z' 'a-z') golang bash -c 'go install github.com/micahyoung/docker-layer-extract@latest && find /go/bin -name docker-layer-extract | xargs mv -t /out'
  

Either a will output the docker-layer-extract binary to your current directory

Usage

Extract your docker image to a tarball

$ docker save <my image tag> -o <my image file>.tar

Extract newest layer from image tarball

$ docker-layer-extract --imagefile <my image file>.tar extract \
--newest \
--layerfile <my extract layer>.tar

List layers in image tarball

$ docker-layer-extract --imagefile <my image file>.tar list 
...
Layer 3:  ID: e51c8d4beda7dffeeb0b0b38fdae6a22e53377207f8c089cb24e35771ebb1506
  Command: `cmd /S /C C:\vc_redist.x64.exe /quiet /install`

Extract a layer from image tarball

$ docker-layer-extract --imagefile <my image file>.tar extract \
--layerid e51c8d4beda7dffeeb0b0b38fdae6a22e53377207f8c089cb24e35771ebb1506 \
--layerfile <my extract layer>.tar

Windows Tarball format

On Windows, the extracted layer embeds Windows-specific values in a PAX header. These values are useful for Docker but not compatible with most tar implementations. To strip these headers when extracting, use the --strip-pax option.

Viewing Hive Delta Entries

Each *_Delta file is a registry hive file and can be viewed using regedit

• Open Regedit
• Click on HKEY_LOCAL_MACHINE
• Click File -> Load Hive
• Navigate to your delta file example System_Delta and open
• Choose a memorable, non-conflicting Key Name to load it under (ex: Temp_System_Delta)

To close:

• Click on Key Name (ex: Temp_System_Delta)
• Click File -> Unload Hive
• Confirm