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