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|
{ config, lib, pkgs, ... }:
with lib;
with builtins;
let
cfg = config.virtualisation;
sanitizeImageName = image: replaceStrings ["/"] ["-"] image.imageName;
hash = drv: head (split "-" (baseNameOf drv.outPath));
# The label of an ext4 FS is limited to 16 bytes
labelFromImage = image: substring 0 16 (hash image);
# The Docker image is loaded and some files from /var/lib/docker/
# are written into a qcow image.
preload = image: pkgs.vmTools.runInLinuxVM (
pkgs.runCommand "docker-preload-image-${sanitizeImageName image}" {
buildInputs = with pkgs; [ docker e2fsprogs utillinux curl kmod ];
preVM = pkgs.vmTools.createEmptyImage {
size = cfg.dockerPreloader.qcowSize;
fullName = "docker-deamon-image.qcow2";
};
}
''
mkfs.ext4 /dev/vda
e2label /dev/vda ${labelFromImage image}
mkdir -p /var/lib/docker
mount -t ext4 /dev/vda /var/lib/docker
modprobe overlay
# from https://github.com/tianon/cgroupfs-mount/blob/master/cgroupfs-mount
mount -t tmpfs -o uid=0,gid=0,mode=0755 cgroup /sys/fs/cgroup
cd /sys/fs/cgroup
for sys in $(awk '!/^#/ { if ($4 == 1) print $1 }' /proc/cgroups); do
mkdir -p $sys
if ! mountpoint -q $sys; then
if ! mount -n -t cgroup -o $sys cgroup $sys; then
rmdir $sys || true
fi
fi
done
dockerd -H tcp://127.0.0.1:5555 -H unix:///var/run/docker.sock &
until $(curl --output /dev/null --silent --connect-timeout 2 http://127.0.0.1:5555); do
printf '.'
sleep 1
done
docker load -i ${image}
kill %1
find /var/lib/docker/ -maxdepth 1 -mindepth 1 -not -name "image" -not -name "overlay2" | xargs rm -rf
'');
preloadedImages = map preload cfg.dockerPreloader.images;
in
{
options.virtualisation.dockerPreloader = {
images = mkOption {
default = [ ];
type = types.listOf types.package;
description =
''
A list of Docker images to preload (in the /var/lib/docker directory).
'';
};
qcowSize = mkOption {
default = 1024;
type = types.int;
description =
''
The size (MB) of qcow files.
'';
};
};
config = mkIf (cfg.dockerPreloader.images != []) {
assertions = [{
# If docker.storageDriver is null, Docker choose the storage
# driver. So, in this case, we cannot be sure overlay2 is used.
assertion = cfg.docker.storageDriver == "overlay2"
|| cfg.docker.storageDriver == "overlay"
|| cfg.docker.storageDriver == null;
message = "The Docker image Preloader only works with overlay2 storage driver!";
}];
virtualisation.qemu.options =
map (path: "-drive if=virtio,file=${path}/disk-image.qcow2,readonly,media=cdrom,format=qcow2")
preloadedImages;
# All attached QCOW files are mounted and their contents are linked
# to /var/lib/docker/ in order to make image available.
systemd.services.docker-preloader = {
description = "Preloaded Docker images";
wantedBy = ["docker.service"];
after = ["network.target"];
path = with pkgs; [ mount rsync jq ];
script = ''
mkdir -p /var/lib/docker/overlay2/l /var/lib/docker/image/overlay2
echo '{}' > /tmp/repositories.json
for i in ${concatStringsSep " " (map labelFromImage cfg.dockerPreloader.images)}; do
mkdir -p /mnt/docker-images/$i
# The ext4 label is limited to 16 bytes
mount /dev/disk/by-label/$(echo $i | cut -c1-16) -o ro,noload /mnt/docker-images/$i
find /mnt/docker-images/$i/overlay2/ -maxdepth 1 -mindepth 1 -not -name l\
-exec ln -s '{}' /var/lib/docker/overlay2/ \;
cp -P /mnt/docker-images/$i/overlay2/l/* /var/lib/docker/overlay2/l/
rsync -a /mnt/docker-images/$i/image/ /var/lib/docker/image/
# Accumulate image definitions
cp /tmp/repositories.json /tmp/repositories.json.tmp
jq -s '.[0] * .[1]' \
/tmp/repositories.json.tmp \
/mnt/docker-images/$i/image/overlay2/repositories.json \
> /tmp/repositories.json
done
mv /tmp/repositories.json /var/lib/docker/image/overlay2/repositories.json
'';
serviceConfig = {
Type = "oneshot";
};
};
};
}
|