ba666011a6
This is a bit of a thorny issue. See, the actual `diskSize` variable is
for the *total* disk size, not for the filesystem!
The automatic numbers are meant to compute the *filesystem* required
space. So we have to add any other reserved space!
We have different requirements for reserved space. E.g. there could be
none (when it's actually a filesystem image). There could also be 1MiB
for alignment for an MBR image, legacy+gpt needs 2MiB, then GPT with an
ESP ("bootSize") needs to take the boot partition and GPT size into
account too!
Though luckily(?) for this latter situation we can cheat! As noted in the
change, `bootSize` is NOT the boot partition size. It is actually the
offset where the target filesystem starts.
389 lines
13 KiB
Nix
389 lines
13 KiB
Nix
{ pkgs
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, lib
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, # The NixOS configuration to be installed onto the disk image.
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config
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, # The size of the disk, in megabytes.
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# if "auto" size is calculated based on the contents copied to it and
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# additionalSpace is taken into account.
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diskSize ? "auto"
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, # additional disk space to be added to the image if diskSize "auto"
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# is used
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additionalSpace ? "512M"
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, # size of the boot partition, is only used if partitionTableType is
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# either "efi" or "hybrid"
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# This will be undersized slightly, as this is actually the offset of
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# the end of the partition. Generally it will be 1MiB smaller.
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bootSize ? "256M"
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, # The files and directories to be placed in the target file system.
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# This is a list of attribute sets {source, target, mode, user, group} where
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# `source' is the file system object (regular file or directory) to be
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# grafted in the file system at path `target', `mode' is a string containing
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# the permissions that will be set (ex. "755"), `user' and `group' are the
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# user and group name that will be set as owner of the files.
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# `mode', `user', and `group' are optional.
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# When setting one of `user' or `group', the other needs to be set too.
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contents ? []
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, # Type of partition table to use; either "legacy", "efi", or "none".
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# For "efi" images, the GPT partition table is used and a mandatory ESP
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# partition of reasonable size is created in addition to the root partition.
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# For "legacy", the msdos partition table is used and a single large root
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# partition is created.
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# For "legacy+gpt", the GPT partition table is used, a 1MiB no-fs partition for
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# use by the bootloader is created, and a single large root partition is
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# created.
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# For "hybrid", the GPT partition table is used and a mandatory ESP
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# partition of reasonable size is created in addition to the root partition.
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# Also a legacy MBR will be present.
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# For "none", no partition table is created. Enabling `installBootLoader`
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# most likely fails as GRUB will probably refuse to install.
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partitionTableType ? "legacy"
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, # The root file system type.
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fsType ? "ext4"
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, # Filesystem label
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label ? "nixos"
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, # The initial NixOS configuration file to be copied to
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# /etc/nixos/configuration.nix.
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configFile ? null
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, # Shell code executed after the VM has finished.
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postVM ? ""
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, name ? "nixos-disk-image"
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, # Disk image format, one of qcow2, qcow2-compressed, vdi, vpc, raw.
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format ? "raw"
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}:
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assert partitionTableType == "legacy" || partitionTableType == "legacy+gpt" || partitionTableType == "efi" || partitionTableType == "hybrid" || partitionTableType == "none";
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# We use -E offset=X below, which is only supported by e2fsprogs
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assert partitionTableType != "none" -> fsType == "ext4";
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# Either both or none of {user,group} need to be set
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assert lib.all
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(attrs: ((attrs.user or null) == null)
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== ((attrs.group or null) == null))
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contents;
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with lib;
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let format' = format; in let
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format = if format' == "qcow2-compressed" then "qcow2" else format';
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compress = optionalString (format' == "qcow2-compressed") "-c";
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filename = "nixos." + {
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qcow2 = "qcow2";
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vdi = "vdi";
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vpc = "vhd";
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raw = "img";
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}.${format} or format;
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rootPartition = { # switch-case
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legacy = "1";
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"legacy+gpt" = "2";
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efi = "2";
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hybrid = "3";
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}.${partitionTableType};
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partitionDiskScript = { # switch-case
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legacy = ''
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parted --script $diskImage -- \
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mklabel msdos \
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mkpart primary ext4 1MiB -1
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'';
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"legacy+gpt" = ''
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parted --script $diskImage -- \
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mklabel gpt \
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mkpart no-fs 1MB 2MB \
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set 1 bios_grub on \
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align-check optimal 1 \
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mkpart primary ext4 2MB -1 \
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align-check optimal 2 \
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print
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'';
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efi = ''
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parted --script $diskImage -- \
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mklabel gpt \
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mkpart ESP fat32 8MiB ${bootSize} \
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set 1 boot on \
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mkpart primary ext4 ${bootSize} -1
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'';
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hybrid = ''
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parted --script $diskImage -- \
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mklabel gpt \
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mkpart ESP fat32 8MiB ${bootSize} \
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set 1 boot on \
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mkpart no-fs 0 1024KiB \
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set 2 bios_grub on \
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mkpart primary ext4 ${bootSize} -1
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'';
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none = "";
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}.${partitionTableType};
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nixpkgs = cleanSource pkgs.path;
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# FIXME: merge with channel.nix / make-channel.nix.
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channelSources = pkgs.runCommand "nixos-${config.system.nixos.version}" {} ''
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mkdir -p $out
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cp -prd ${nixpkgs.outPath} $out/nixos
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chmod -R u+w $out/nixos
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if [ ! -e $out/nixos/nixpkgs ]; then
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ln -s . $out/nixos/nixpkgs
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fi
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rm -rf $out/nixos/.git
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echo -n ${config.system.nixos.versionSuffix} > $out/nixos/.version-suffix
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'';
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binPath = with pkgs; makeBinPath (
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[ rsync
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util-linux
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parted
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e2fsprogs
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lkl
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config.system.build.nixos-install
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config.system.build.nixos-enter
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nix
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] ++ stdenv.initialPath);
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# I'm preserving the line below because I'm going to search for it across nixpkgs to consolidate
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# image building logic. The comment right below this now appears in 4 different places in nixpkgs :)
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# !!! should use XML.
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sources = map (x: x.source) contents;
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targets = map (x: x.target) contents;
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modes = map (x: x.mode or "''") contents;
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users = map (x: x.user or "''") contents;
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groups = map (x: x.group or "''") contents;
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closureInfo = pkgs.closureInfo { rootPaths = [ config.system.build.toplevel channelSources ]; };
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blockSize = toString (4 * 1024); # ext4fs block size (not block device sector size)
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prepareImage = ''
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export PATH=${binPath}
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# Yes, mkfs.ext4 takes different units in different contexts. Fun.
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sectorsToKilobytes() {
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echo $(( ( "$1" * 512 ) / 1024 ))
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}
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sectorsToBytes() {
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echo $(( "$1" * 512 ))
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}
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# Given lines of numbers, adds them together
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sum_lines() {
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local acc=0
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while read -r number; do
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acc=$((acc+number))
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done
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echo "$acc"
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}
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# Approximative percentage of reserved space in an ext4 fs over 512MiB.
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# 0.05208587646484375
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# × 1000, integer part: 52
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compute_fudge() {
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echo $(( $1 * 52 / 1000 ))
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}
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mkdir $out
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root="$PWD/root"
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mkdir -p $root
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# Copy arbitrary other files into the image
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# Semi-shamelessly copied from make-etc.sh. I (@copumpkin) shall factor this stuff out as part of
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# https://github.com/NixOS/nixpkgs/issues/23052.
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set -f
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sources_=(${concatStringsSep " " sources})
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targets_=(${concatStringsSep " " targets})
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modes_=(${concatStringsSep " " modes})
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set +f
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for ((i = 0; i < ''${#targets_[@]}; i++)); do
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source="''${sources_[$i]}"
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target="''${targets_[$i]}"
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mode="''${modes_[$i]}"
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if [ -n "$mode" ]; then
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rsync_chmod_flags="--chmod=$mode"
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else
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rsync_chmod_flags=""
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fi
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# Unfortunately cptofs only supports modes, not ownership, so we can't use
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# rsync's --chown option. Instead, we change the ownerships in the
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# VM script with chown.
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rsync_flags="-a --no-o --no-g $rsync_chmod_flags"
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if [[ "$source" =~ '*' ]]; then
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# If the source name contains '*', perform globbing.
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mkdir -p $root/$target
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for fn in $source; do
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rsync $rsync_flags "$fn" $root/$target/
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done
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else
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mkdir -p $root/$(dirname $target)
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if ! [ -e $root/$target ]; then
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rsync $rsync_flags $source $root/$target
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else
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echo "duplicate entry $target -> $source"
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exit 1
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fi
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fi
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done
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export HOME=$TMPDIR
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# Provide a Nix database so that nixos-install can copy closures.
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export NIX_STATE_DIR=$TMPDIR/state
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nix-store --load-db < ${closureInfo}/registration
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chmod 755 "$TMPDIR"
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echo "running nixos-install..."
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nixos-install --root $root --no-bootloader --no-root-passwd \
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--system ${config.system.build.toplevel} --channel ${channelSources} --substituters ""
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diskImage=nixos.raw
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${if diskSize == "auto" then ''
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${if partitionTableType == "efi" || partitionTableType == "hybrid" then ''
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# Add the GPT at the end
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gptSpace=$(( 512 * 34 * 1 ))
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# Normally we'd need to account for alignment and things, if bootSize
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# represented the actual size of the boot partition. But it instead
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# represents the offset at which it ends.
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# So we know bootSize is the reserved space in front of the partition.
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reservedSpace=$(( gptSpace + $(numfmt --from=iec '${bootSize}') ))
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'' else if partitionTableType == "legacy+gpt" then ''
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# Add the GPT at the end
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gptSpace=$(( 512 * 34 * 1 ))
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# And include the bios_grub partition; the ext4 partition starts at 2MB exactly.
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reservedSpace=$(( gptSpace + 2 * 1024*1024 ))
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'' else if partitionTableType == "legacy" then ''
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# Add the 1MiB aligned reserved space (includes MBR)
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reservedSpace=$(( 1024*1024 ))
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'' else ''
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reservedSpace=0
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''}
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additionalSpace=$(( $(numfmt --from=iec '${additionalSpace}') + reservedSpace ))
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# Compute required space in filesystem blocks
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diskUsage=$(find . ! -type d -exec 'du' '--apparent-size' '--block-size' "${blockSize}" '{}' ';' | cut -f1 | sum_lines)
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# Each inode takes space!
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numInodes=$(find . | wc -l)
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# Convert to bytes, inodes take two blocks each!
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diskUsage=$(( (diskUsage + 2 * numInodes) * ${blockSize} ))
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# Then increase the required space to account for the reserved blocks.
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fudge=$(compute_fudge $diskUsage)
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requiredFilesystemSpace=$(( diskUsage + fudge ))
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diskSize=$(( requiredFilesystemSpace + additionalSpace ))
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truncate -s "$diskSize" $diskImage
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printf "Automatic disk size...\n"
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printf " Closure space use: %d bytes\n" $diskUsage
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printf " fudge: %d bytes\n" $fudge
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printf " Filesystem size needed: %d bytes\n" $requiredFilesystemSpace
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printf " Additional space: %d bytes\n" $additionalSpace
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printf " Disk image size: %d bytes\n" $diskSize
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'' else ''
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truncate -s ${toString diskSize}M $diskImage
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''}
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${partitionDiskScript}
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${if partitionTableType != "none" then ''
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# Get start & length of the root partition in sectors to $START and $SECTORS.
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eval $(partx $diskImage -o START,SECTORS --nr ${rootPartition} --pairs)
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mkfs.${fsType} -b ${blockSize} -F -L ${label} $diskImage -E offset=$(sectorsToBytes $START) $(sectorsToKilobytes $SECTORS)K
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'' else ''
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mkfs.${fsType} -b ${blockSize} -F -L ${label} $diskImage
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''}
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echo "copying staging root to image..."
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cptofs -p ${optionalString (partitionTableType != "none") "-P ${rootPartition}"} -t ${fsType} -i $diskImage $root/* / ||
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(echo >&2 "ERROR: cptofs failed. diskSize might be too small for closure."; exit 1)
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'';
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in pkgs.vmTools.runInLinuxVM (
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pkgs.runCommand name
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{ preVM = prepareImage;
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buildInputs = with pkgs; [ util-linux e2fsprogs dosfstools ];
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postVM = ''
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${if format == "raw" then ''
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mv $diskImage $out/${filename}
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'' else ''
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${pkgs.qemu}/bin/qemu-img convert -f raw -O ${format} ${compress} $diskImage $out/${filename}
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''}
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diskImage=$out/${filename}
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${postVM}
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'';
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memSize = 1024;
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}
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''
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export PATH=${binPath}:$PATH
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rootDisk=${if partitionTableType != "none" then "/dev/vda${rootPartition}" else "/dev/vda"}
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# Some tools assume these exist
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ln -s vda /dev/xvda
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ln -s vda /dev/sda
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mountPoint=/mnt
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mkdir $mountPoint
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mount $rootDisk $mountPoint
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# Create the ESP and mount it. Unlike e2fsprogs, mkfs.vfat doesn't support an
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# '-E offset=X' option, so we can't do this outside the VM.
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${optionalString (partitionTableType == "efi" || partitionTableType == "hybrid") ''
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mkdir -p /mnt/boot
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mkfs.vfat -n ESP /dev/vda1
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mount /dev/vda1 /mnt/boot
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''}
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# Install a configuration.nix
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mkdir -p /mnt/etc/nixos
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${optionalString (configFile != null) ''
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cp ${configFile} /mnt/etc/nixos/configuration.nix
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''}
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# Set up core system link, GRUB, etc.
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NIXOS_INSTALL_BOOTLOADER=1 nixos-enter --root $mountPoint -- /nix/var/nix/profiles/system/bin/switch-to-configuration boot
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# The above scripts will generate a random machine-id and we don't want to bake a single ID into all our images
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rm -f $mountPoint/etc/machine-id
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# Set the ownerships of the contents. The modes are set in preVM.
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# No globbing on targets, so no need to set -f
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targets_=(${concatStringsSep " " targets})
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users_=(${concatStringsSep " " users})
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groups_=(${concatStringsSep " " groups})
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for ((i = 0; i < ''${#targets_[@]}; i++)); do
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target="''${targets_[$i]}"
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user="''${users_[$i]}"
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group="''${groups_[$i]}"
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if [ -n "$user$group" ]; then
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# We have to nixos-enter since we need to use the user and group of the VM
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nixos-enter --root $mountPoint -- chown -R "$user:$group" "$target"
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fi
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done
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umount -R /mnt
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# Make sure resize2fs works. Note that resize2fs has stricter criteria for resizing than a normal
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# mount, so the `-c 0` and `-i 0` don't affect it. Setting it to `now` doesn't produce deterministic
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# output, of course, but we can fix that when/if we start making images deterministic.
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${optionalString (fsType == "ext4") ''
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tune2fs -T now -c 0 -i 0 $rootDisk
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''}
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''
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)
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