nixpkgs/pkgs/build-support/docker/default.nix

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{
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bashInteractive,
buildPackages,
cacert,
callPackage,
closureInfo,
coreutils,
docker,
e2fsprogs,
findutils,
go,
jq,
jshon,
lib,
makeWrapper,
moreutils,
nix,
pigz,
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rsync,
runCommand,
runtimeShell,
shadow,
skopeo,
stdenv,
storeDir ? builtins.storeDir,
substituteAll,
symlinkJoin,
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util-linux,
vmTools,
writeReferencesToFile,
writeScript,
writeText,
writeTextDir,
writePython3,
system, # Note: This is the cross system we're compiling for
}:
let
mkDbExtraCommand = contents: let
contentsList = if builtins.isList contents then contents else [ contents ];
in ''
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."
export NIX_REMOTE=local?root=$PWD
# A user is required by nix
# https://github.com/NixOS/nix/blob/9348f9291e5d9e4ba3c4347ea1b235640f54fd79/src/libutil/util.cc#L478
export USER=nobody
${buildPackages.nix}/bin/nix-store --load-db < ${closureInfo {rootPaths = contentsList;}}/registration
mkdir -p nix/var/nix/gcroots/docker/
for i in ${lib.concatStringsSep " " contentsList}; do
ln -s $i nix/var/nix/gcroots/docker/$(basename $i)
done;
'';
# The OCI Image specification recommends that configurations use values listed
# in the Go Language document for GOARCH.
# Reference: https://github.com/opencontainers/image-spec/blob/master/config.md#properties
# For the mapping from Nixpkgs system parameters to GOARCH, we can reuse the
# mapping from the go package.
defaultArch = go.GOARCH;
in
rec {
examples = callPackage ./examples.nix {
inherit buildImage buildLayeredImage fakeNss pullImage shadowSetup buildImageWithNixDb;
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};
pullImage = let
fixName = name: builtins.replaceStrings ["/" ":"] ["-" "-"] name;
in
{ imageName
# To find the digest of an image, you can use skopeo:
# see doc/functions.xml
, imageDigest
, sha256
, os ? "linux"
, arch ? defaultArch
# This is used to set name to the pulled image
, finalImageName ? imageName
# This used to set a tag to the pulled image
, finalImageTag ? "latest"
, name ? fixName "docker-image-${finalImageName}-${finalImageTag}.tar"
}:
runCommand name {
inherit imageDigest;
imageName = finalImageName;
imageTag = finalImageTag;
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impureEnvVars = lib.fetchers.proxyImpureEnvVars;
outputHashMode = "flat";
outputHashAlgo = "sha256";
outputHash = sha256;
nativeBuildInputs = lib.singleton skopeo;
SSL_CERT_FILE = "${cacert.out}/etc/ssl/certs/ca-bundle.crt";
sourceURL = "docker://${imageName}@${imageDigest}";
destNameTag = "${finalImageName}:${finalImageTag}";
} ''
skopeo --insecure-policy --tmpdir=$TMPDIR --override-os ${os} --override-arch ${arch} copy "$sourceURL" "docker-archive://$out:$destNameTag"
'';
# 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 etc.
tarsum = runCommand "tarsum" {
nativeBuildInputs = [ go ];
} ''
mkdir tarsum
cd tarsum
cp ${./tarsum.go} tarsum.go
export GOPATH=$(pwd)
export GOCACHE="$TMPDIR/go-cache"
mkdir -p src/github.com/docker/docker/pkg
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ln -sT ${docker.moby.src}/pkg/tarsum src/github.com/docker/docker/pkg/tarsum
go build
mkdir -p $out/bin
cp tarsum $out/bin/
'';
# buildEnv creates symlinks to dirs, which is hard to edit inside the overlay VM
mergeDrvs = {
derivations,
onlyDeps ? false
}:
runCommand "merge-drvs" {
inherit derivations onlyDeps;
} ''
if [[ -n "$onlyDeps" ]]; then
echo $derivations > $out
exit 0
fi
mkdir $out
for derivation in $derivations; do
echo "Merging $derivation..."
if [[ -d "$derivation" ]]; then
# If it's a directory, copy all of its contents into $out.
cp -drf --preserve=mode -f $derivation/* $out/
else
# Otherwise treat the derivation as a tarball and extract it
# into $out.
tar -C $out -xpf $drv || true
fi
done
'';
# Helper for setting up the base files for managing users and
# groups, only if such files don't exist already. It is suitable for
# being used in a runAsRoot script.
shadowSetup = ''
export PATH=${shadow}/bin:$PATH
mkdir -p /etc/pam.d
if [[ ! -f /etc/passwd ]]; then
echo "root:x:0:0::/root:${runtimeShell}" > /etc/passwd
echo "root:!x:::::::" > /etc/shadow
fi
if [[ ! -f /etc/group ]]; then
echo "root:x:0:" > /etc/group
echo "root:x::" > /etc/gshadow
fi
if [[ ! -f /etc/pam.d/other ]]; then
cat > /etc/pam.d/other <<EOF
account sufficient pam_unix.so
auth sufficient pam_rootok.so
password requisite pam_unix.so nullok sha512
session required pam_unix.so
EOF
fi
if [[ ! -f /etc/login.defs ]]; then
touch /etc/login.defs
fi
'';
# Run commands in a virtual machine.
runWithOverlay = {
name,
fromImage ? null,
fromImageName ? null,
fromImageTag ? null,
diskSize ? 1024,
preMount ? "",
postMount ? "",
postUmount ? ""
}:
let
result = vmTools.runInLinuxVM (
runCommand name {
preVM = vmTools.createEmptyImage {
size = diskSize;
fullName = "docker-run-disk";
};
inherit fromImage fromImageName fromImageTag;
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nativeBuildInputs = [ util-linux e2fsprogs jshon rsync jq ];
} ''
mkdir disk
mkfs /dev/${vmTools.hd}
mount /dev/${vmTools.hd} disk
cd disk
if [[ -n "$fromImage" ]]; then
echo "Unpacking base image..."
mkdir image
tar -C image -xpf "$fromImage"
if [[ -n "$fromImageName" ]] && [[ -n "$fromImageTag" ]]; then
parentID="$(
cat "image/manifest.json" |
jq -r '.[] | select(.RepoTags | contains([$desiredTag])) | rtrimstr(".json")' \
--arg desiredTag "$fromImageName:$fromImageTag"
)"
else
echo "From-image name or tag wasn't set. Reading the first ID."
parentID="$(cat "image/manifest.json" | jq -r '.[0].Config | rtrimstr(".json")')"
fi
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
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cat ./image/manifest.json | jq -r '.[0].Layers | .[]' > layer-list
else
touch layer-list
fi
# Unpack all of the parent layers into the image.
lowerdir=""
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
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extractionID=0
for layerTar in $(tac layer-list); do
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
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echo "Unpacking layer $layerTar"
extractionID=$((extractionID + 1))
mkdir -p image/$extractionID/layer
tar -C image/$extractionID/layer -xpf image/$layerTar
rm image/$layerTar
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
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find image/$extractionID/layer -name ".wh.*" -exec bash -c 'name="$(basename {}|sed "s/^.wh.//")"; mknod "$(dirname {})/$name" c 0 0; rm {}' \;
# Get the next lower directory and continue the loop.
lowerdir=image/$extractionID/layer''${lowerdir:+:}$lowerdir
done
mkdir work
mkdir layer
mkdir mnt
${lib.optionalString (preMount != "") ''
# Execute pre-mount steps
echo "Executing pre-mount steps..."
${preMount}
''}
if [ -n "$lowerdir" ]; then
mount -t overlay overlay -olowerdir=$lowerdir,workdir=work,upperdir=layer mnt
else
mount --bind layer mnt
fi
${lib.optionalString (postMount != "") ''
# Execute post-mount steps
echo "Executing post-mount steps..."
${postMount}
''}
umount mnt
(
cd layer
cmd='name="$(basename {})"; touch "$(dirname {})/.wh.$name"; rm "{}"'
find . -type c -exec bash -c "$cmd" \;
)
${postUmount}
'');
in
runCommand name {} ''
mkdir -p $out
cd ${result}
cp layer.tar json VERSION $out
'';
exportImage = { name ? fromImage.name, fromImage, fromImageName ? null, fromImageTag ? null, diskSize ? 1024 }:
runWithOverlay {
inherit name fromImage fromImageName fromImageTag diskSize;
postMount = ''
echo "Packing raw image..."
tar -C mnt --hard-dereference --sort=name --mtime="@$SOURCE_DATE_EPOCH" -cf $out .
'';
};
# Create an executable shell script which has the coreutils in its
# PATH. Since root scripts are executed in a blank environment, even
# things like `ls` or `echo` will be missing.
shellScript = name: text:
writeScript name ''
#!${runtimeShell}
set -e
export PATH=${coreutils}/bin:/bin
${text}
'';
# Create a "layer" (set of files).
mkPureLayer = {
# Name of the layer
name,
# JSON containing configuration and metadata for this layer.
baseJson,
# Files to add to the layer.
contents ? null,
# When copying the contents into the image, preserve symlinks to
# directories (see `rsync -K`). Otherwise, transform those symlinks
# into directories.
keepContentsDirlinks ? false,
# Additional commands to run on the layer before it is tar'd up.
extraCommands ? "", uid ? 0, gid ? 0
}:
runCommand "docker-layer-${name}" {
inherit baseJson contents extraCommands;
nativeBuildInputs = [ jshon rsync tarsum ];
}
''
mkdir layer
if [[ -n "$contents" ]]; then
echo "Adding contents..."
for item in $contents; do
echo "Adding $item"
rsync -a${if keepContentsDirlinks then "K" else "k"} --chown=0:0 $item/ layer/
done
else
echo "No contents to add to layer."
fi
chmod ug+w layer
if [[ -n "$extraCommands" ]]; then
(cd layer; eval "$extraCommands")
fi
# Tar up the layer and throw it into 'layer.tar'.
echo "Packing layer..."
mkdir $out
tarhash=$(tar -C layer --hard-dereference --sort=name --mtime="@$SOURCE_DATE_EPOCH" --owner=${toString uid} --group=${toString gid} -cf - . | tee -p $out/layer.tar | tarsum)
# Add a 'checksum' field to the JSON, with the value set to the
# checksum of the tarball.
cat ${baseJson} | jshon -s "$tarhash" -i checksum > $out/json
# Indicate to docker that we're using schema version 1.0.
echo -n "1.0" > $out/VERSION
echo "Finished building layer '${name}'"
'';
# Make a "root" layer; required if we need to execute commands as a
# privileged user on the image. The commands themselves will be
# performed in a virtual machine sandbox.
mkRootLayer = {
# Name of the image.
name,
# Script to run as root. Bash.
runAsRoot,
# Files to add to the layer. If null, an empty layer will be created.
contents ? null,
# When copying the contents into the image, preserve symlinks to
# directories (see `rsync -K`). Otherwise, transform those symlinks
# into directories.
keepContentsDirlinks ? false,
# JSON containing configuration and metadata for this layer.
baseJson,
# Existing image onto which to append the new layer.
fromImage ? null,
# Name of the image we're appending onto.
fromImageName ? null,
# Tag of the image we're appending onto.
fromImageTag ? null,
# How much disk to allocate for the temporary virtual machine.
diskSize ? 1024,
# Commands (bash) to run on the layer; these do not require sudo.
extraCommands ? ""
}:
# Generate an executable script from the `runAsRoot` text.
let
runAsRootScript = shellScript "run-as-root.sh" runAsRoot;
extraCommandsScript = shellScript "extra-commands.sh" extraCommands;
in runWithOverlay {
name = "docker-layer-${name}";
inherit fromImage fromImageName fromImageTag diskSize;
preMount = lib.optionalString (contents != null && contents != []) ''
echo "Adding contents..."
for item in ${toString contents}; do
echo "Adding $item..."
rsync -a${if keepContentsDirlinks then "K" else "k"} --chown=0:0 $item/ layer/
done
chmod ug+w layer
'';
postMount = ''
mkdir -p mnt/{dev,proc,sys} mnt${storeDir}
# Mount /dev, /sys and the nix store as shared folders.
mount --rbind /dev mnt/dev
mount --rbind /sys mnt/sys
mount --rbind ${storeDir} mnt${storeDir}
# Execute the run as root script. See 'man unshare' for
# details on what's going on here; basically this command
# means that the runAsRootScript will be executed in a nearly
# completely isolated environment.
unshare -imnpuf --mount-proc chroot mnt ${runAsRootScript}
# Unmount directories and remove them.
umount -R mnt/dev mnt/sys mnt${storeDir}
rmdir --ignore-fail-on-non-empty \
mnt/dev mnt/proc mnt/sys mnt${storeDir} \
mnt$(dirname ${storeDir})
'';
postUmount = ''
(cd layer; ${extraCommandsScript})
echo "Packing layer..."
mkdir -p $out
tarhash=$(tar -C layer --hard-dereference --sort=name --mtime="@$SOURCE_DATE_EPOCH" -cf - . |
tee -p $out/layer.tar |
${tarsum}/bin/tarsum)
cat ${baseJson} | jshon -s "$tarhash" -i checksum > $out/json
# Indicate to docker that we're using schema version 1.0.
echo -n "1.0" > $out/VERSION
echo "Finished building layer '${name}'"
'';
};
buildLayeredImage = {name, ...}@args:
dockerTools.buildLayeredImage: init Create a many-layered Docker Image. Implements much less than buildImage: - Doesn't support specific uids/gids - Doesn't support runninng commands after building - Doesn't require qemu - Doesn't create mutable copies of the files in the path - Doesn't support parent images If you want those feature, I recommend using buildLayeredImage as an input to buildImage. Notably, it does support: - Caching low level, common paths based on a graph traversial algorithm, see referencesByPopularity in 0a80233487993256e811f566b1c80a40394c03d6 - Configurable number of layers. If you're not using AUFS or not extending the image, you can specify a larger number of layers at build time: pkgs.dockerTools.buildLayeredImage { name = "hello"; maxLayers = 128; config.Cmd = [ "${pkgs.gitFull}/bin/git" ]; }; - Parallelized creation of the layers, improving build speed. - The contents of the image includes the closure of the configuration, so you don't have to specify paths in contents and config. With buildImage, paths referred to by the config were not included automatically in the image. Thus, if you wanted to call Git, you had to specify it twice: pkgs.dockerTools.buildImage { name = "hello"; contents = [ pkgs.gitFull ]; config.Cmd = [ "${pkgs.gitFull}/bin/git" ]; }; buildLayeredImage on the other hand includes the runtime closure of the config when calculating the contents of the image: pkgs.dockerTools.buildImage { name = "hello"; config.Cmd = [ "${pkgs.gitFull}/bin/git" ]; }; Minor Problems - If any of the store paths change, every layer will be rebuilt in the nix-build. However, beacuse the layers are bit-for-bit reproducable, when these images are loaded in to Docker they will match existing layers and not be imported or uploaded twice. Common Questions - Aren't Docker layers ordered? No. People who have used a Dockerfile before assume Docker's Layers are inherently ordered. However, this is not true -- Docker layers are content-addressable and are not explicitly layered until they are composed in to an Image. - What happens if I have more than maxLayers of store paths? The first (maxLayers-2) most "popular" paths will have their own individual layers, then layer #(maxLayers-1) will contain all the remaining "unpopular" paths, and finally layer #(maxLayers) will contain the Image configuration.
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let
stream = streamLayeredImage args;
dockerTools.buildLayeredImage: init Create a many-layered Docker Image. Implements much less than buildImage: - Doesn't support specific uids/gids - Doesn't support runninng commands after building - Doesn't require qemu - Doesn't create mutable copies of the files in the path - Doesn't support parent images If you want those feature, I recommend using buildLayeredImage as an input to buildImage. Notably, it does support: - Caching low level, common paths based on a graph traversial algorithm, see referencesByPopularity in 0a80233487993256e811f566b1c80a40394c03d6 - Configurable number of layers. If you're not using AUFS or not extending the image, you can specify a larger number of layers at build time: pkgs.dockerTools.buildLayeredImage { name = "hello"; maxLayers = 128; config.Cmd = [ "${pkgs.gitFull}/bin/git" ]; }; - Parallelized creation of the layers, improving build speed. - The contents of the image includes the closure of the configuration, so you don't have to specify paths in contents and config. With buildImage, paths referred to by the config were not included automatically in the image. Thus, if you wanted to call Git, you had to specify it twice: pkgs.dockerTools.buildImage { name = "hello"; contents = [ pkgs.gitFull ]; config.Cmd = [ "${pkgs.gitFull}/bin/git" ]; }; buildLayeredImage on the other hand includes the runtime closure of the config when calculating the contents of the image: pkgs.dockerTools.buildImage { name = "hello"; config.Cmd = [ "${pkgs.gitFull}/bin/git" ]; }; Minor Problems - If any of the store paths change, every layer will be rebuilt in the nix-build. However, beacuse the layers are bit-for-bit reproducable, when these images are loaded in to Docker they will match existing layers and not be imported or uploaded twice. Common Questions - Aren't Docker layers ordered? No. People who have used a Dockerfile before assume Docker's Layers are inherently ordered. However, this is not true -- Docker layers are content-addressable and are not explicitly layered until they are composed in to an Image. - What happens if I have more than maxLayers of store paths? The first (maxLayers-2) most "popular" paths will have their own individual layers, then layer #(maxLayers-1) will contain all the remaining "unpopular" paths, and finally layer #(maxLayers) will contain the Image configuration.
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in
runCommand "${name}.tar.gz" {
inherit (stream) imageName;
passthru = { inherit (stream) imageTag; };
nativeBuildInputs = [ pigz ];
} "${stream} | pigz -nT > $out";
dockerTools.buildLayeredImage: init Create a many-layered Docker Image. Implements much less than buildImage: - Doesn't support specific uids/gids - Doesn't support runninng commands after building - Doesn't require qemu - Doesn't create mutable copies of the files in the path - Doesn't support parent images If you want those feature, I recommend using buildLayeredImage as an input to buildImage. Notably, it does support: - Caching low level, common paths based on a graph traversial algorithm, see referencesByPopularity in 0a80233487993256e811f566b1c80a40394c03d6 - Configurable number of layers. If you're not using AUFS or not extending the image, you can specify a larger number of layers at build time: pkgs.dockerTools.buildLayeredImage { name = "hello"; maxLayers = 128; config.Cmd = [ "${pkgs.gitFull}/bin/git" ]; }; - Parallelized creation of the layers, improving build speed. - The contents of the image includes the closure of the configuration, so you don't have to specify paths in contents and config. With buildImage, paths referred to by the config were not included automatically in the image. Thus, if you wanted to call Git, you had to specify it twice: pkgs.dockerTools.buildImage { name = "hello"; contents = [ pkgs.gitFull ]; config.Cmd = [ "${pkgs.gitFull}/bin/git" ]; }; buildLayeredImage on the other hand includes the runtime closure of the config when calculating the contents of the image: pkgs.dockerTools.buildImage { name = "hello"; config.Cmd = [ "${pkgs.gitFull}/bin/git" ]; }; Minor Problems - If any of the store paths change, every layer will be rebuilt in the nix-build. However, beacuse the layers are bit-for-bit reproducable, when these images are loaded in to Docker they will match existing layers and not be imported or uploaded twice. Common Questions - Aren't Docker layers ordered? No. People who have used a Dockerfile before assume Docker's Layers are inherently ordered. However, this is not true -- Docker layers are content-addressable and are not explicitly layered until they are composed in to an Image. - What happens if I have more than maxLayers of store paths? The first (maxLayers-2) most "popular" paths will have their own individual layers, then layer #(maxLayers-1) will contain all the remaining "unpopular" paths, and finally layer #(maxLayers) will contain the Image configuration.
2018-09-25 14:53:42 +00:00
# 1. extract the base image
# 2. create the layer
# 3. add layer deps to the layer itself, diffing with the base image
# 4. compute the layer id
# 5. put the layer in the image
# 6. repack the image
buildImage = args@{
# Image name.
name,
# Image tag, when null then the nix output hash will be used.
tag ? null,
# Parent image, to append to.
fromImage ? null,
# Name of the parent image; will be read from the image otherwise.
fromImageName ? null,
# Tag of the parent image; will be read from the image otherwise.
fromImageTag ? null,
# Files to put on the image (a nix store path or list of paths).
contents ? null,
# When copying the contents into the image, preserve symlinks to
# directories (see `rsync -K`). Otherwise, transform those symlinks
# into directories.
keepContentsDirlinks ? false,
# Docker config; e.g. what command to run on the container.
config ? null,
# Optional bash script to run on the files prior to fixturizing the layer.
extraCommands ? "", uid ? 0, gid ? 0,
# Optional bash script to run as root on the image when provisioning.
runAsRoot ? null,
# Size of the virtual machine disk to provision when building the image.
diskSize ? 1024,
# Time of creation of the image.
created ? "1970-01-01T00:00:01Z",
}:
let
baseName = baseNameOf name;
# Create a JSON blob of the configuration. Set the date to unix zero.
baseJson = let
pure = writeText "${baseName}-config.json" (builtins.toJSON {
inherit created config;
architecture = defaultArch;
os = "linux";
});
impure = runCommand "${baseName}-config.json"
{ nativeBuildInputs = [ jq ]; }
''
jq ".created = \"$(TZ=utc date --iso-8601="seconds")\"" ${pure} > $out
'';
in if created == "now" then impure else pure;
layer =
if runAsRoot == null
then mkPureLayer {
name = baseName;
inherit baseJson contents keepContentsDirlinks extraCommands uid gid;
} else mkRootLayer {
name = baseName;
inherit baseJson fromImage fromImageName fromImageTag
contents keepContentsDirlinks runAsRoot diskSize
extraCommands;
};
result = runCommand "docker-image-${baseName}.tar.gz" {
nativeBuildInputs = [ jshon pigz coreutils findutils jq moreutils ];
# Image name and tag must be lowercase
imageName = lib.toLower name;
imageTag = if tag == null then "" else lib.toLower tag;
inherit fromImage baseJson;
layerClosure = writeReferencesToFile layer;
passthru.buildArgs = args;
passthru.layer = layer;
passthru.imageTag =
if tag != null
then lib.toLower tag
else
lib.head (lib.strings.splitString "-" (baseNameOf result.outPath));
# Docker can't be made to run darwin binaries
meta.badPlatforms = lib.platforms.darwin;
} ''
${lib.optionalString (tag == null) ''
outName="$(basename "$out")"
outHash=$(echo "$outName" | cut -d - -f 1)
imageTag=$outHash
''}
# Print tar contents:
# 1: Interpreted as relative to the root directory
# 2: With no trailing slashes on directories
# This is useful for ensuring that the output matches the
# values generated by the "find" command
ls_tar() {
for f in $(tar -tf $1 | xargs realpath -ms --relative-to=.); do
if [[ "$f" != "." ]]; then
echo "/$f"
fi
done
}
mkdir image
touch baseFiles
baseEnvs='[]'
if [[ -n "$fromImage" ]]; then
echo "Unpacking base image..."
tar -C image -xpf "$fromImage"
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
2018-12-04 17:18:06 +00:00
# Store the layers and the environment variables from the base image
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
2018-12-04 17:18:06 +00:00
cat ./image/manifest.json | jq -r '.[0].Layers | .[]' > layer-list
configName="$(cat ./image/manifest.json | jq -r '.[0].Config')"
baseEnvs="$(cat "./image/$configName" | jq '.config.Env // []')"
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
2018-12-04 17:18:06 +00:00
# Extract the parentID from the manifest
if [[ -n "$fromImageName" ]] && [[ -n "$fromImageTag" ]]; then
parentID="$(
cat "image/manifest.json" |
jq -r '.[] | select(.RepoTags | contains([$desiredTag])) | rtrimstr(".json")' \
--arg desiredTag "$fromImageName:$fromImageTag"
)"
else
echo "From-image name or tag wasn't set. Reading the first ID."
parentID="$(cat "image/manifest.json" | jq -r '.[0].Config | rtrimstr(".json")')"
fi
# Otherwise do not import the base image configuration and manifest
chmod a+w image image/*.json
rm -f image/*.json
for l in image/*/layer.tar; do
ls_tar $l >> baseFiles
done
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
2018-12-04 17:18:06 +00:00
else
touch layer-list
fi
chmod -R ug+rw image
mkdir temp
cp ${layer}/* temp/
chmod ug+w temp/*
for dep in $(cat $layerClosure); do
find $dep >> layerFiles
done
echo "Adding layer..."
# Record the contents of the tarball with ls_tar.
ls_tar temp/layer.tar >> baseFiles
# Append nix/store directory to the layer so that when the layer is loaded in the
# image /nix/store has read permissions for non-root users.
# nix/store is added only if the layer has /nix/store paths in it.
if [ $(wc -l < $layerClosure) -gt 1 ] && [ $(grep -c -e "^/nix/store$" baseFiles) -eq 0 ]; then
mkdir -p nix/store
chmod -R 555 nix
echo "./nix" >> layerFiles
echo "./nix/store" >> layerFiles
fi
# Get the files in the new layer which were *not* present in
# the old layer, and record them as newFiles.
comm <(sort -n baseFiles|uniq) \
<(sort -n layerFiles|uniq|grep -v ${layer}) -1 -3 > newFiles
# Append the new files to the layer.
tar -rpf temp/layer.tar --hard-dereference --sort=name --mtime="@$SOURCE_DATE_EPOCH" \
--owner=0 --group=0 --no-recursion --files-from newFiles
echo "Adding meta..."
# If we have a parentID, add it to the json metadata.
if [[ -n "$parentID" ]]; then
cat temp/json | jshon -s "$parentID" -i parent > tmpjson
mv tmpjson temp/json
fi
# 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)
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
# Add the new layer ID to the end of the layer list
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
2018-12-04 17:18:06 +00:00
(
cat layer-list
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
2018-12-04 17:18:06 +00:00
# originally this used `sed -i "1i$layerID" layer-list`, but
# would fail if layer-list was completely empty.
echo "$layerID/layer.tar"
) | sponge layer-list
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
2018-12-04 17:18:06 +00:00
# Create image json and image manifest
imageJson=$(cat ${baseJson} | jq '.config.Env = $baseenv + .config.Env' --argjson baseenv "$baseEnvs")
imageJson=$(echo "$imageJson" | jq ". + {\"rootfs\": {\"diff_ids\": [], \"type\": \"layers\"}}")
manifestJson=$(jq -n "[{\"RepoTags\":[\"$imageName:$imageTag\"]}]")
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
2018-12-04 17:18:06 +00:00
for layerTar in $(cat ./layer-list); do
dockerTools.buildImage: support using a layered image in fromImage Docker images used to be, essentially, a linked list of layers. Each layer would have a tarball and a json document pointing to its parent, and the image pointed to the top layer: imageA ----> layerA | v layerB | v layerC The current image spec changed this format to where the Image defined the order and set of layers: imageA ---> layerA |--> layerB `--> layerC For backwards compatibility, docker produces images which follow both specs: layers point to parents, and images also point to the entire list: imageA ---> layerA | | | v |--> layerB | | | v `--> layerC This is nice for tooling which supported the older version and never updated to support the newer format. Our `buildImage` code only supported the old version, so in order for `buildImage` to properly generate an image based on another image with `fromImage`, the parent image's layers must fully support the old mechanism. This is not a problem in general, but is a problem with `buildLayeredImage`. `buildLayeredImage` creates images with newer image spec, because individual store paths don't have a guaranteed parent layer. Including a specific parent ID in the layer's json makes the output less likely to cache hit when published or pulled. This means until now, `buildLayeredImage` could not be the input to `buildImage`. The changes in this PR change `buildImage` to only use the layer's manifest when locating parent IDs. This does break buildImage on extremely old Docker images, though I do wonder how many of these exist. This work has been sponsored by Target.
2018-12-04 17:18:06 +00:00
layerChecksum=$(sha256sum image/$layerTar | cut -d ' ' -f1)
imageJson=$(echo "$imageJson" | jq ".history |= . + [{\"created\": \"$(jq -r .created ${baseJson})\"}]")
# diff_ids order is from the bottom-most to top-most layer
imageJson=$(echo "$imageJson" | jq ".rootfs.diff_ids |= . + [\"sha256:$layerChecksum\"]")
manifestJson=$(echo "$manifestJson" | jq ".[0].Layers |= . + [\"$layerTar\"]")
done
imageJsonChecksum=$(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 --hard-dereference --sort=name --mtime="@$SOURCE_DATE_EPOCH" --owner=0 --group=0 --xform s:'^./':: -c . | pigz -nT > $out
echo "Finished."
'';
in
result;
# Provide a /etc/passwd and /etc/group that contain root and nobody.
# Useful when packaging binaries that insist on using nss to look up
# username/groups (like nginx).
2020-12-02 13:51:06 +00:00
# /bin/sh is fine to not exist, and provided by another shim.
fakeNss = symlinkJoin {
name = "fake-nss";
paths = [
(writeTextDir "etc/passwd" ''
root:x:0:0:root user:/var/empty:/bin/sh
nobody:x:65534:65534:nobody:/var/empty:/bin/sh
'')
(writeTextDir "etc/group" ''
root:x:0:
nobody:x:65534:
'')
(runCommand "var-empty" {} ''
mkdir -p $out/var/empty
'')
];
};
2020-12-02 13:51:06 +00:00
# This provides /bin/sh, pointing to bashInteractive.
binSh = runCommand "bin-sh" {} ''
mkdir -p $out/bin
ln -s ${bashInteractive}/bin/bash $out/bin/sh
'';
# 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 = (mkDbExtraCommand contents) + extraCommands;
})
);
buildLayeredImageWithNixDb = args@{ contents ? null, extraCommands ? "", ... }: (
buildLayeredImage (args // {
extraCommands = (mkDbExtraCommand contents) + extraCommands;
})
);
streamLayeredImage = {
# Image Name
name,
# Image tag, the Nix's output hash will be used if null
tag ? null,
# Files to put on the image (a nix store path or list of paths).
contents ? [],
# Docker config; e.g. what command to run on the container.
config ? {},
# Time of creation of the image. Passing "now" will make the
# created date be the time of building.
created ? "1970-01-01T00:00:01Z",
# Optional bash script to run on the files prior to fixturizing the layer.
extraCommands ? "",
# We pick 100 to ensure there is plenty of room for extension. I
# believe the actual maximum is 128.
maxLayers ? 100
}:
assert
(lib.assertMsg (maxLayers > 1)
"the maxLayers argument of dockerTools.buildLayeredImage function must be greather than 1 (current value: ${toString maxLayers})");
let
streamScript = writePython3 "stream" {} ./stream_layered_image.py;
baseJson = writeText "${name}-base.json" (builtins.toJSON {
inherit config;
architecture = defaultArch;
os = "linux";
});
contentsList = if builtins.isList contents then contents else [ contents ];
# We store the customisation layer as a tarball, to make sure that
# things like permissions set on 'extraCommands' are not overriden
# by Nix. Then we precompute the sha256 for performance.
customisationLayer = symlinkJoin {
name = "${name}-customisation-layer";
paths = contentsList;
inherit extraCommands;
postBuild = ''
mv $out old_out
(cd old_out; eval "$extraCommands" )
mkdir $out
tar \
--owner 0 --group 0 --mtime "@$SOURCE_DATE_EPOCH" \
--hard-dereference \
-C old_out \
-cf $out/layer.tar .
sha256sum $out/layer.tar \
| cut -f 1 -d ' ' \
> $out/checksum
'';
};
closureRoots = [ baseJson ] ++ contentsList;
overallClosure = writeText "closure" (lib.concatStringsSep " " closureRoots);
# These derivations are only created as implementation details of docker-tools,
# so they'll be excluded from the created images.
unnecessaryDrvs = [ baseJson overallClosure ];
conf = runCommand "${name}-conf.json" {
inherit maxLayers created;
imageName = lib.toLower name;
passthru.imageTag =
if tag != null
then tag
else
lib.head (lib.strings.splitString "-" (baseNameOf conf.outPath));
paths = buildPackages.referencesByPopularity overallClosure;
nativeBuildInputs = [ jq ];
} ''
${if (tag == null) then ''
outName="$(basename "$out")"
outHash=$(echo "$outName" | cut -d - -f 1)
imageTag=$outHash
'' else ''
imageTag="${tag}"
''}
# convert "created" to iso format
if [[ "$created" != "now" ]]; then
created="$(date -Iseconds -d "$created")"
fi
paths() {
cat $paths ${lib.concatMapStringsSep " "
(path: "| (grep -v ${path} || true)")
unnecessaryDrvs}
}
# Create $maxLayers worth of Docker Layers, one layer per store path
# unless there are more paths than $maxLayers. In that case, create
# $maxLayers-1 for the most popular layers, and smush the remainaing
# store paths in to one final layer.
#
# The following code is fiddly w.r.t. ensuring every layer is
# created, and that no paths are missed. If you change the
# following lines, double-check that your code behaves properly
# when the number of layers equals:
# maxLayers-1, maxLayers, and maxLayers+1, 0
store_layers="$(
paths |
jq -sR '
rtrimstr("\n") | split("\n")
| (.[:$maxLayers-1] | map([.])) + [ .[$maxLayers-1:] ]
| map(select(length > 0))
' \
--argjson maxLayers "$(( maxLayers - 1 ))" # one layer will be taken up by the customisation layer
)"
cat ${baseJson} | jq '
. + {
"store_layers": $store_layers,
"customisation_layer", $customisation_layer,
"repo_tag": $repo_tag,
"created": $created
}
' --argjson store_layers "$store_layers" \
--arg customisation_layer ${customisationLayer} \
--arg repo_tag "$imageName:$imageTag" \
--arg created "$created" |
tee $out
'';
result = runCommand "stream-${name}" {
inherit (conf) imageName;
passthru = {
inherit (conf) imageTag;
# Distinguish tarballs and exes at the Nix level so functions that
# take images can know in advance how the image is supposed to be used.
isExe = true;
};
nativeBuildInputs = [ makeWrapper ];
} ''
makeWrapper ${streamScript} $out --add-flags ${conf}
'';
in result;
}