Docker image layer data preview quick experimental Bash script

1_image_layers.sh

# /usr/bin/env bash

_totalSize=0;

_Fmt() ( numfmt --from=iec --to=iec --suffix B --format='%0.2f' -- "${1}K"; );
_DirSize() ( sudo -- bash -c 'if [[ -d "$1" ]]; then du -ks -- "$1" | cut -f1; else printf ?; fi;' - "$1"; );
_TreePath() ( sudo -- tree -avr --charset=ascii --dirsfirst --du -- "$1"; );

_PreviewLayers()
{
    declare resultFilepart="$1";
    shift;
    declare layers=( "$@" );
    shift $#;

    declare layersCount="${#layers[@]}";
    declare indexPadding="${#layersCount}";
    declare i;

    for (( i=0; i < layersCount; i++ ));
    do
        declare layerDirpath="${layers[i]}";
        declare layerId="${layerDirpath%/*}";
        declare layerId="${layerId##*/}";

        declare layerSize="$( _DirSize "$layerDirpath"; )" || return $?;
        declare _totalSize="$(( _totalSize + layerSize ))";
        declare message;

        printf -v message -- $"  [%${indexPadding}s] Layer '%s' ~ %10s B (%10s) -> %10s B (%10s)\n" \
            "$i" \
            "$layerDirpath" \
            "$layerSize" "$( _Fmt "$layerSize"; )" \
            "$_totalSize" "$( _Fmt "$_totalSize"; )";

        printf '%s' "$message";

        (
            printf '%s\n' "$message";

            _TreePath "$layerDirpath" || return $?;
        ) \
            &> "${resultFilepart}_${i}-${layersCount}_${layerId:0:16}.txt";
    done
}

_Main() (
    declare imageName="$1";
    shift;

    docker images -- "$imageName" || return $?;

    printf '\n';

    declare imageId="$( docker images -q -- "$imageName"; )" || return $?;
    declare currentDirpath; currentDirpath="$( pwd -P; )";
    declare time; time="$( date -u -- '+%F_%H_%M_%S_Z'; )";
    declare layerDataDirpart="${currentDirpath}/${time}";

    printf '# LowerDir\n\n';

    declare lowerDirLayers=();

    readarray -td ':' -- lowerDirLayers < <(
        docker image inspect --format '{{json .GraphDriver.Data}}' "$imageId" \
            | jq '.LowerDir' \
            | perl -pe 's/["\n]//g';
    ) \
        || return $?;

    _PreviewLayers "${layerDataDirpart}_lower" "${lowerDirLayers[@]}";

    printf '\n# UpperDir\n\n';

    declare upperDirLayers=();

    readarray -td ':' -- upperDirLayers < <(
        docker image inspect --format '{{json .GraphDriver.Data}}' "$imageId" \
            | jq '.UpperDir' \
            | perl -pe 's/["\n]//g';
    ) \
        || return $?;

    _PreviewLayers "${layerDataDirpart}_upper" "${upperDirLayers[@]}";

    printf '\nTotal: %s B (%s)\n\n' "$_totalSize" "$( _Fmt "$_totalSize"; )";
    printf $'Hurray! Please check layer contents in files:\n\n';

    ls -la -- "$layerDataDirpart"*;

    printf '\n';
)

_Main "$@";

2_test.txt

$ ./image_layers.sh node;

REPOSITORY   TAG       IMAGE ID       CREATED       SIZE
node         latest    e15446acc41f   2 weeks ago   1.12GB

# LowerDir

  [0] Layer '/var/lib/docker/overlay2/a875f17bdc2dd04a2439457ed0b5aec4f740432a3661f08a2e6eca59d57661e3/diff' ~       5280 B (    5.16MB) ->       5280 B (    5.16MB)
  [1] Layer '/var/lib/docker/overlay2/222440f39327db7c3f0e4c94ec8aacffe536e600981771e823a750f254c8a7f0/diff' ~     198816 B (  194.16MB) ->     204096 B (  199.32MB)
  [2] Layer '/var/lib/docker/overlay2/eff01b43d034758d03ed0e49fcc166a16d244bae463eeaf26f004dbfe6e5dbd4/diff' ~         68 B (   68.00KB) ->     204164 B (  199.38MB)
  [3] Layer '/var/lib/docker/overlay2/1936ff5cba642f1888f3069ec3223826a0f43ece29a123a3027f83eef6e25bd7/diff' ~     603888 B (  589.74MB) ->     808052 B (  789.12MB)
  [4] Layer '/var/lib/docker/overlay2/538f0145f18bd799cdb53c2b315f10ca4adc4ff0645a2ce62bc111bcb73a6c3d/diff' ~     189060 B (  184.63MB) ->     997112 B (  973.75MB)
  [5] Layer '/var/lib/docker/overlay2/59a261372580a2be1a0ea6d2bdf36ff43da1928102a6e51c4050da6822da45c4/diff' ~      51040 B (   49.85MB) ->    1048152 B ( 1023.59MB)
  [6] Layer '/var/lib/docker/overlay2/4eb4ac9cfa5e72a81fdad84a78e03ffaab0b47a187573f696bc4c8112290d70f/diff' ~     129640 B (  126.61MB) ->    1177792 B (    1.13GB)

# UpperDir

  [0] Layer '/var/lib/docker/overlay2/7dd3b1e349edda701561d44cfdc6b0af308e9bdc86758f6d10b010dcf7d54e45/diff' ~         20 B (   20.00KB) ->         20 B (   20.00KB)

Total: 0 B (0.00B)

Hurray! Please check layer contents in files:

-rw-rw-r-- 1 user user   1113 Dec  6 17:26 /home/user/temp/2024-12-06_17_26_46_Z_lower_0-7_a875f17bdc2dd04a.txt
-rw-rw-r-- 1 user user 391294 Dec  6 17:26 /home/user/temp/2024-12-06_17_26_46_Z_lower_1-7_222440f39327db7c.txt
-rw-rw-r-- 1 user user    881 Dec  6 17:26 /home/user/temp/2024-12-06_17_26_46_Z_lower_2-7_eff01b43d034758d.txt
-rw-rw-r-- 1 user user 696494 Dec  6 17:26 /home/user/temp/2024-12-06_17_26_46_Z_lower_3-7_1936ff5cba642f18.txt
-rw-rw-r-- 1 user user 347925 Dec  6 17:26 /home/user/temp/2024-12-06_17_26_46_Z_lower_4-7_538f0145f18bd799.txt
-rw-rw-r-- 1 user user 104948 Dec  6 17:26 /home/user/temp/2024-12-06_17_26_46_Z_lower_5-7_59a261372580a2be.txt
-rw-rw-r-- 1 user user 325745 Dec  6 17:26 /home/user/temp/2024-12-06_17_26_46_Z_lower_6-7_4eb4ac9cfa5e72a8.txt
-rw-rw-r-- 1 user user    462 Dec  6 17:26 /home/user/temp/2024-12-06_17_26_46_Z_upper_0-1_7dd3b1e349edda70.txt

3_2024-12-06_17_26_46_Z_lower_0-7_a875f17bdc2dd04a.txt

  [0] Layer '/var/lib/docker/overlay2/a875f17bdc2dd04a2439457ed0b5aec4f740432a3661f08a2e6eca59d57661e3/diff' ~       5280 B (    5.16MB) ->       5280 B (    5.16MB)

[    5373312]  /var/lib/docker/overlay2/a875f17bdc2dd04a2439457ed0b5aec4f740432a3661f08a2e6eca59d57661e3/diff
|-- [      12345]  usr
|   `-- [       8249]  local
|       `-- [       4153]  bin
|           |-- [         30]  yarnpkg -> /opt/yarn-v1.22.22/bin/yarnpkg
|           `-- [         27]  yarn -> /opt/yarn-v1.22.22/bin/yarn
`-- [    5356871]  opt
    `-- [    5352775]  yarn-v1.22.22
        |-- [    5334753]  lib
        |   |-- [       9910]  v8-compile-cache.js
        |   `-- [    5320747]  cli.js
        |-- [       6242]  bin
        |   |-- [         30]  yarnpkg.cmd
        |   |-- [         42]  yarnpkg
        |   |-- [       1015]  yarn.js
        |   |-- [         34]  yarn.cmd
        |   `-- [       1025]  yarn
        |-- [       2342]  preinstall.js
        |-- [        634]  package.json
        |-- [       3353]  README.md
        `-- [       1355]  LICENSE

    21415932 bytes used in 8 directories, 13 files