86d9b09c9b
The image json is not exactly the same as the layer json, therefore I
changed the implementation to use the `baseJson` which doesn’t include
layer specific details like `id`, `size` or the checksum of the layer.
Also the `history` entry was missing in the image json. I’m not totally
sure if this field is required, but a I got an error from a docker
registry when I’ve tried to receive the distribution manifest of an
image without those `history` entry:
GET: `http://<registry-host>/v2/<imageName>/manifests/<imageTag>`
```json
{
"errors": [
{
"code": "MANIFEST_INVALID",
"message": "manifest invalid",
"detail": {}
}
]
}
```
I’ve also used a while loop to iterate over all layers which should make
sure that the order of the layers is correct. Previously `find` was
used and I’m not sure if the order was always correct.
535 lines
17 KiB
Nix
535 lines
17 KiB
Nix
{
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callPackage,
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coreutils,
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docker,
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e2fsprogs,
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findutils,
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go,
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jshon,
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jq,
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lib,
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pkgs,
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pigz,
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runCommand,
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rsync,
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shadow,
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stdenv,
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storeDir ? builtins.storeDir,
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utillinux,
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vmTools,
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writeReferencesToFile,
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writeScript,
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writeText,
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}:
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# WARNING: this API is unstable and may be subject to backwards-incompatible changes in the future.
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rec {
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examples = import ./examples.nix {
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inherit pkgs buildImage pullImage shadowSetup;
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};
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pullImage = callPackage ./pull.nix {};
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# We need to sum layer.tar, not a directory, hence tarsum instead of nix-hash.
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# And we cannot untar it, because then we cannot preserve permissions ecc.
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tarsum = runCommand "tarsum" {
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buildInputs = [ go ];
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} ''
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mkdir tarsum
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cd tarsum
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cp ${./tarsum.go} tarsum.go
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export GOPATH=$(pwd)
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mkdir src
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ln -sT ${docker.src}/components/engine/pkg/tarsum src/tarsum
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go build
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cp tarsum $out
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'';
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# buildEnv creates symlinks to dirs, which is hard to edit inside the overlay VM
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mergeDrvs = {
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derivations,
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onlyDeps ? false
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}:
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runCommand "merge-drvs" {
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inherit derivations onlyDeps;
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} ''
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if [[ -n "$onlyDeps" ]]; then
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echo $derivations > $out
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exit 0
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fi
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mkdir $out
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for derivation in $derivations; do
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echo "Merging $derivation..."
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if [[ -d "$derivation" ]]; then
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# If it's a directory, copy all of its contents into $out.
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cp -drf --preserve=mode -f $derivation/* $out/
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else
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# Otherwise treat the derivation as a tarball and extract it
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# into $out.
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tar -C $out -xpf $drv || true
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fi
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done
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'';
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# Helper for setting up the base files for managing users and
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# groups, only if such files don't exist already. It is suitable for
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# being used in a runAsRoot script.
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shadowSetup = ''
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export PATH=${shadow}/bin:$PATH
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mkdir -p /etc/pam.d
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if [[ ! -f /etc/passwd ]]; then
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echo "root:x:0:0::/root:${stdenv.shell}" > /etc/passwd
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echo "root:!x:::::::" > /etc/shadow
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fi
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if [[ ! -f /etc/group ]]; then
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echo "root:x:0:" > /etc/group
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echo "root:x::" > /etc/gshadow
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fi
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if [[ ! -f /etc/pam.d/other ]]; then
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cat > /etc/pam.d/other <<EOF
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account sufficient pam_unix.so
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auth sufficient pam_rootok.so
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password requisite pam_unix.so nullok sha512
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session required pam_unix.so
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EOF
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fi
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if [[ ! -f /etc/login.defs ]]; then
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touch /etc/login.defs
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fi
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'';
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# Run commands in a virtual machine.
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runWithOverlay = {
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name,
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fromImage ? null,
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fromImageName ? null,
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fromImageTag ? null,
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diskSize ? 1024,
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preMount ? "",
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postMount ? "",
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postUmount ? ""
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}:
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vmTools.runInLinuxVM (
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runCommand name {
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preVM = vmTools.createEmptyImage {
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size = diskSize;
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fullName = "docker-run-disk";
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};
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inherit fromImage fromImageName fromImageTag;
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buildInputs = [ utillinux e2fsprogs jshon rsync ];
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} ''
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rm -rf $out
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mkdir disk
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mkfs /dev/${vmTools.hd}
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mount /dev/${vmTools.hd} disk
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cd disk
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if [[ -n "$fromImage" ]]; then
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echo "Unpacking base image..."
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mkdir image
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tar -C image -xpf "$fromImage"
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# If the image name isn't set, read it from the image repository json.
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if [[ -z "$fromImageName" ]]; then
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fromImageName=$(jshon -k < image/repositories | head -n 1)
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echo "From-image name wasn't set. Read $fromImageName."
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fi
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# If the tag isn't set, use the name as an index into the json
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# and read the first key found.
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if [[ -z "$fromImageTag" ]]; then
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fromImageTag=$(jshon -e $fromImageName -k < image/repositories \
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| head -n1)
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echo "From-image tag wasn't set. Read $fromImageTag."
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fi
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# Use the name and tag to get the parent ID field.
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parentID=$(jshon -e $fromImageName -e $fromImageTag -u \
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< image/repositories)
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fi
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# Unpack all of the parent layers into the image.
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lowerdir=""
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while [[ -n "$parentID" ]]; do
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echo "Unpacking layer $parentID"
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mkdir -p image/$parentID/layer
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tar -C image/$parentID/layer -xpf image/$parentID/layer.tar
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rm image/$parentID/layer.tar
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find image/$parentID/layer -name ".wh.*" -exec bash -c 'name="$(basename {}|sed "s/^.wh.//")"; mknod "$(dirname {})/$name" c 0 0; rm {}' \;
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# Get the next lower directory and continue the loop.
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lowerdir=$lowerdir''${lowerdir:+:}image/$parentID/layer
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parentID=$(cat image/$parentID/json \
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| (jshon -e parent -u 2>/dev/null || true))
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done
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mkdir work
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mkdir layer
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mkdir mnt
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${lib.optionalString (preMount != "") ''
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# Execute pre-mount steps
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echo "Executing pre-mount steps..."
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${preMount}
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''}
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if [ -n "$lowerdir" ]; then
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mount -t overlay overlay -olowerdir=$lowerdir,workdir=work,upperdir=layer mnt
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else
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mount --bind layer mnt
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fi
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${lib.optionalString (postMount != "") ''
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# Execute post-mount steps
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echo "Executing post-mount steps..."
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${postMount}
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''}
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umount mnt
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(
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cd layer
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cmd='name="$(basename {})"; touch "$(dirname {})/.wh.$name"; rm "{}"'
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find . -type c -exec bash -c "$cmd" \;
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)
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${postUmount}
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'');
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exportImage = { name ? fromImage.name, fromImage, fromImageName ? null, fromImageTag ? null, diskSize ? 1024 }:
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runWithOverlay {
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inherit name fromImage fromImageName fromImageTag diskSize;
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postMount = ''
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echo "Packing raw image..."
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tar -C mnt --mtime="@$SOURCE_DATE_EPOCH" -cf $out .
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'';
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};
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# Create an executable shell script which has the coreutils in its
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# PATH. Since root scripts are executed in a blank environment, even
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# things like `ls` or `echo` will be missing.
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shellScript = name: text:
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writeScript name ''
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#!${stdenv.shell}
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set -e
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export PATH=${coreutils}/bin:/bin
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${text}
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'';
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# Create a "layer" (set of files).
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mkPureLayer = {
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# Name of the layer
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name,
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# JSON containing configuration and metadata for this layer.
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baseJson,
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# Files to add to the layer.
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contents ? null,
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# Additional commands to run on the layer before it is tar'd up.
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extraCommands ? "", uid ? 0, gid ? 0
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}:
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runCommand "docker-layer-${name}" {
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inherit baseJson contents extraCommands;
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buildInputs = [ jshon rsync ];
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}
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''
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mkdir layer
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if [[ -n "$contents" ]]; then
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echo "Adding contents..."
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for item in $contents; do
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echo "Adding $item"
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rsync -ak --chown=0:0 $item/ layer/
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done
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else
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echo "No contents to add to layer."
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fi
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chmod ug+w layer
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if [[ -n $extraCommands ]]; then
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(cd layer; eval "$extraCommands")
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fi
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# Tar up the layer and throw it into 'layer.tar'.
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echo "Packing layer..."
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mkdir $out
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tar -C layer --mtime="@$SOURCE_DATE_EPOCH" --owner=${toString uid} --group=${toString gid} -cf $out/layer.tar .
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# Compute a checksum of the tarball.
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echo "Computing layer checksum..."
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tarsum=$(${tarsum} < $out/layer.tar)
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# Add a 'checksum' field to the JSON, with the value set to the
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# checksum of the tarball.
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cat ${baseJson} | jshon -s "$tarsum" -i checksum > $out/json
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# Indicate to docker that we're using schema version 1.0.
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echo -n "1.0" > $out/VERSION
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echo "Finished building layer '${name}'"
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'';
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# Make a "root" layer; required if we need to execute commands as a
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# privileged user on the image. The commands themselves will be
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# performed in a virtual machine sandbox.
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mkRootLayer = {
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# Name of the image.
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name,
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# Script to run as root. Bash.
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runAsRoot,
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# Files to add to the layer. If null, an empty layer will be created.
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contents ? null,
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# JSON containing configuration and metadata for this layer.
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baseJson,
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# Existing image onto which to append the new layer.
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fromImage ? null,
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# Name of the image we're appending onto.
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fromImageName ? null,
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# Tag of the image we're appending onto.
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fromImageTag ? null,
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# How much disk to allocate for the temporary virtual machine.
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diskSize ? 1024,
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# Commands (bash) to run on the layer; these do not require sudo.
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extraCommands ? ""
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}:
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# Generate an executable script from the `runAsRoot` text.
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let runAsRootScript = shellScript "run-as-root.sh" runAsRoot;
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in runWithOverlay {
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name = "docker-layer-${name}";
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inherit fromImage fromImageName fromImageTag diskSize;
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preMount = lib.optionalString (contents != null && contents != []) ''
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echo "Adding contents..."
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for item in ${toString contents}; do
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echo "Adding $item..."
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rsync -ak --chown=0:0 $item/ layer/
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done
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chmod ug+w layer
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'';
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postMount = ''
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mkdir -p mnt/{dev,proc,sys} mnt${storeDir}
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# Mount /dev, /sys and the nix store as shared folders.
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mount --rbind /dev mnt/dev
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mount --rbind /sys mnt/sys
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mount --rbind ${storeDir} mnt${storeDir}
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# Execute the run as root script. See 'man unshare' for
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# details on what's going on here; basically this command
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# means that the runAsRootScript will be executed in a nearly
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# completely isolated environment.
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unshare -imnpuf --mount-proc chroot mnt ${runAsRootScript}
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# Unmount directories and remove them.
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umount -R mnt/dev mnt/sys mnt${storeDir}
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rmdir --ignore-fail-on-non-empty \
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mnt/dev mnt/proc mnt/sys mnt${storeDir} \
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mnt$(dirname ${storeDir})
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'';
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postUmount = ''
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(cd layer; eval "${extraCommands}")
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echo "Packing layer..."
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mkdir $out
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tar -C layer --mtime="@$SOURCE_DATE_EPOCH" -cf $out/layer.tar .
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# Compute the tar checksum and add it to the output json.
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echo "Computing checksum..."
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ts=$(${tarsum} < $out/layer.tar)
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cat ${baseJson} | jshon -s "$ts" -i checksum > $out/json
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# Indicate to docker that we're using schema version 1.0.
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echo -n "1.0" > $out/VERSION
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echo "Finished building layer '${name}'"
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'';
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};
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# 1. extract the base image
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# 2. create the layer
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# 3. add layer deps to the layer itself, diffing with the base image
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# 4. compute the layer id
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# 5. put the layer in the image
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# 6. repack the image
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buildImage = args@{
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# Image name.
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name,
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# Image tag.
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tag ? "latest",
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# Parent image, to append to.
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fromImage ? null,
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# Name of the parent image; will be read from the image otherwise.
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fromImageName ? null,
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# Tag of the parent image; will be read from the image otherwise.
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fromImageTag ? null,
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# Files to put on the image (a nix store path or list of paths).
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contents ? null,
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# Docker config; e.g. what command to run on the container.
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config ? null,
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# Optional bash script to run on the files prior to fixturizing the layer.
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extraCommands ? "", uid ? 0, gid ? 0,
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# Optional bash script to run as root on the image when provisioning.
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runAsRoot ? null,
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# Size of the virtual machine disk to provision when building the image.
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diskSize ? 1024,
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# Time of creation of the image.
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created ? "1970-01-01T00:00:01Z",
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}:
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let
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baseName = baseNameOf name;
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# Create a JSON blob of the configuration. Set the date to unix zero.
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baseJson = writeText "${baseName}-config.json" (builtins.toJSON {
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inherit created config;
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architecture = "amd64";
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os = "linux";
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});
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layer =
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if runAsRoot == null
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then mkPureLayer {
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name = baseName;
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inherit baseJson contents extraCommands uid gid;
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} else mkRootLayer {
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name = baseName;
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inherit baseJson fromImage fromImageName fromImageTag
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contents runAsRoot diskSize extraCommands;
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};
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result = runCommand "docker-image-${baseName}.tar.gz" {
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buildInputs = [ jshon pigz coreutils findutils jq ];
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# Image name and tag must be lowercase
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imageName = lib.toLower name;
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imageTag = lib.toLower tag;
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inherit fromImage baseJson;
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layerClosure = writeReferencesToFile layer;
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passthru.buildArgs = args;
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passthru.layer = layer;
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} ''
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# Print tar contents:
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# 1: Interpreted as relative to the root directory
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# 2: With no trailing slashes on directories
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# This is useful for ensuring that the output matches the
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# values generated by the "find" command
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ls_tar() {
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for f in $(tar -tf $1 | xargs realpath -ms --relative-to=.); do
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if [[ "$f" != "." ]]; then
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echo "/$f"
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fi
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done
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}
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mkdir image
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touch baseFiles
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if [[ -n "$fromImage" ]]; then
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echo "Unpacking base image..."
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tar -C image -xpf "$fromImage"
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# Do not import the base image configuration and manifest
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chmod a+w image image/*.json
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rm -f image/*.json
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if [[ -z "$fromImageName" ]]; then
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fromImageName=$(jshon -k < image/repositories|head -n1)
|
|
fi
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|
if [[ -z "$fromImageTag" ]]; then
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fromImageTag=$(jshon -e $fromImageName -k \
|
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< image/repositories|head -n1)
|
|
fi
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|
parentID=$(jshon -e $fromImageName -e $fromImageTag -u \
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< image/repositories)
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for l in image/*/layer.tar; do
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ls_tar $l >> baseFiles
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done
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fi
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chmod -R ug+rw image
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mkdir temp
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cp ${layer}/* temp/
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chmod ug+w temp/*
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echo "$(dirname ${storeDir})" >> layerFiles
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echo '${storeDir}' >> layerFiles
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for dep in $(cat $layerClosure); do
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find $dep >> layerFiles
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done
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echo "Adding layer..."
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# Record the contents of the tarball with ls_tar.
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|
ls_tar temp/layer.tar >> baseFiles
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# Get the files in the new layer which were *not* present in
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# the old layer, and record them as newFiles.
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|
comm <(sort -n baseFiles|uniq) \
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<(sort -n layerFiles|uniq|grep -v ${layer}) -1 -3 > newFiles
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|
# Append the new files to the layer.
|
|
tar -rpf temp/layer.tar --mtime="@$SOURCE_DATE_EPOCH" \
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--owner=0 --group=0 --no-recursion --files-from newFiles
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|
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echo "Adding meta..."
|
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|
|
# If we have a parentID, add it to the json metadata.
|
|
if [[ -n "$parentID" ]]; then
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cat temp/json | jshon -s "$parentID" -i parent > tmpjson
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|
mv tmpjson temp/json
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|
fi
|
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|
|
# Take the sha256 sum of the generated json and use it as the layer ID.
|
|
# Compute the size and add it to the json under the 'Size' field.
|
|
layerID=$(sha256sum temp/json|cut -d ' ' -f 1)
|
|
size=$(stat --printf="%s" temp/layer.tar)
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cat temp/json | jshon -s "$layerID" -i id -n $size -i Size > tmpjson
|
|
mv tmpjson temp/json
|
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|
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# Use the temp folder we've been working on to create a new image.
|
|
mv temp image/$layerID
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|
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# Create image json and image manifest
|
|
imageJson=$(cat ${baseJson} | jq ". + {\"rootfs\": {\"diff_ids\": [], \"type\": \"layers\"}}")
|
|
manifestJson=$(jq -n "[{\"RepoTags\":[\"$imageName:$imageTag\"]}]")
|
|
currentID=$layerID
|
|
while [[ -n "$currentID" ]]; do
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layerChecksum=$(sha256sum image/$currentID/layer.tar | cut -d ' ' -f1)
|
|
imageJson=$(echo "$imageJson" | jq ".history |= [{\"created\": \"${created}\"}] + .")
|
|
imageJson=$(echo "$imageJson" | jq ".rootfs.diff_ids |= [\"sha256:$layerChecksum\"] + .")
|
|
manifestJson=$(echo "$manifestJson" | jq ".[0].Layers |= [\"$currentID/layer.tar\"] + .")
|
|
|
|
currentID=$(cat image/$currentID/json | (jshon -e parent -u 2>/dev/null || true))
|
|
done
|
|
|
|
imageJsonChecksum=$(echo "$imageJson" | sha256sum | cut -d ' ' -f1)
|
|
echo "$imageJson" > "image/$imageJsonChecksum.json"
|
|
manifestJson=$(echo "$manifestJson" | jq ".[0].Config = \"$imageJsonChecksum.json\"")
|
|
echo "$manifestJson" > image/manifest.json
|
|
|
|
# Store the json under the name image/repositories.
|
|
jshon -n object \
|
|
-n object -s "$layerID" -i "$imageTag" \
|
|
-i "$imageName" > image/repositories
|
|
|
|
# Make the image read-only.
|
|
chmod -R a-w image
|
|
|
|
echo "Cooking the image..."
|
|
tar -C image --mtime="@$SOURCE_DATE_EPOCH" --owner=0 --group=0 --xform s:'./':: -c . | pigz -nT > $out
|
|
|
|
echo "Finished."
|
|
'';
|
|
|
|
in
|
|
result;
|
|
}
|