forked from mirrors/nixpkgs
df589a438e
Currently, the contents closure is copied to the layer but there is no nix database initialization. If pkgs.nix is added in the contents, nix-store doesn't work because there is no nix database. From the contents of the layer, this commit generates and loads the database in the nix store of the container. This only works if there is no parent layer that already have a nix store (to support several nix layers, we would have to merge nix databases of parent layers). We also add an example to play with the nix store inside the container. Note it seems `more` is a missing dependency of the nix package!
578 lines
18 KiB
Nix
578 lines
18 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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nixUnstable,
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perl,
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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 buildImageWithNixDb;
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};
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pullImage =
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let
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nameReplace = name: builtins.replaceStrings ["/" ":"] ["-" "-"] name;
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in
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# For simplicity we only support sha256.
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{ imageName, imageTag ? "latest", imageId ? "${imageName}:${imageTag}"
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, sha256, name ? (nameReplace "docker-image-${imageName}-${imageTag}.tar") }:
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runCommand name {
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impureEnvVars=pkgs.stdenv.lib.fetchers.proxyImpureEnvVars;
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outputHashMode="flat";
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outputHashAlgo="sha256";
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outputHash=sha256;
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}
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"${pkgs.skopeo}/bin/skopeo copy docker://${imageId} docker-archive://$out:${imageId}";
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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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nixRegistration = contents: runCommand "nix-registration" {
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buildInputs = [ nixUnstable perl ];
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# For obtaining the closure of `contents'.
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exportReferencesGraph =
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let contentsList = if builtins.isList contents then contents else [ contents ];
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in map (x: [("closure-" + baseNameOf x) x]) contentsList;
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}
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''
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printRegistration=1 perl ${pkgs.pathsFromGraph} closure-* > $out
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'';
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# Create a "layer" (set of files).
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mkPureLayer = {
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# Name of the layer
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name,
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# JSON containing configuration and metadata for this layer.
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baseJson,
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# Files to add to the layer.
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contents ? null,
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# Additional commands to run on the layer before it is tar'd up.
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extraCommands ? "", uid ? 0, gid ? 0
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}:
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runCommand "docker-layer-${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=$(jshon -k < image/repositories|head -n1)
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fi
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if [[ -z "$fromImageTag" ]]; then
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fromImageTag=$(jshon -e $fromImageName -k \
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< image/repositories|head -n1)
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fi
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parentID=$(jshon -e $fromImageName -e $fromImageTag -u \
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< image/repositories)
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|
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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 ${layer}) -1 -3 > newFiles
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# Append the new files to the layer.
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tar -rpf temp/layer.tar --mtime="@$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.
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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.
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# Compute the size and add it to the json under the 'Size' field.
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layerID=$(sha256sum temp/json|cut -d ' ' -f 1)
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size=$(stat --printf="%s" temp/layer.tar)
|
|
cat temp/json | jshon -s "$layerID" -i id -n $size -i Size > tmpjson
|
|
mv tmpjson temp/json
|
|
|
|
# Use the temp folder we've been working on to create a new image.
|
|
mv temp image/$layerID
|
|
|
|
# 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
|
|
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 > $out
|
|
|
|
echo "Finished."
|
|
'';
|
|
|
|
in
|
|
result;
|
|
|
|
# Build an image and populate its nix database with the provided
|
|
# contents. The main purpose is to be able to use nix commands in
|
|
# the container.
|
|
# Be careful since this doesn't work well with multilayer.
|
|
buildImageWithNixDb = args@{ contents ? null, extraCommands ? "", ... }:
|
|
buildImage (args // {
|
|
extraCommands = ''
|
|
echo "Generating the nix database..."
|
|
echo "Warning: only the database of the deepest Nix layer is loaded."
|
|
echo " If you want to use nix commands in the container, it would"
|
|
echo " be better to only have one layer that contains a nix store."
|
|
# This requires Nix 1.12 or higher
|
|
export NIX_REMOTE=local?root=$PWD
|
|
${nixUnstable}/bin/nix-store --load-db < ${nixRegistration contents}
|
|
'' + extraCommands;
|
|
});
|
|
}
|