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make-disk-image: add hybrid and dynamic sized images #89331

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make-disk-image: add hybrid and dynamic sized images #89331

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79 changes: 56 additions & 23 deletions nixos/lib/make-disk-image.nix
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Expand Up @@ -5,21 +5,32 @@
config

, # The size of the disk, in megabytes.
diskSize
# if "auto" size is calculated based on the contents copied to it and
# additionalSpace is taken into account.
diskSize ? "auto"

# The files and directories to be placed in the target file system.
, # additional disk space to be added to the image if diskSize "auto"
# is used
additionalSpace ? "512M"

, # size of the boot partition, is only used if partitionTableType is
# either "efi" or "hybrid"
bootSize ? "256M"

, # The files and directories to be placed in the target file system.
# This is a list of attribute sets {source, target} where `source'
# is the file system object (regular file or directory) to be
# grafted in the file system at path `target'.
, contents ? []
contents ? []

, # Type of partition table to use; either "legacy", "efi", or "none".
# For "efi" images, the GPT partition table is used and a mandatory ESP
# partition of reasonable size is created in addition to the root partition.
# If `installBootLoader` is true, GRUB will be installed in EFI mode.
# For "legacy", the msdos partition table is used and a single large root
# partition is created. If `installBootLoader` is true, GRUB will be
# installed in legacy mode.
# partition is created.
# For "hybrid", the GPT partition table is used and a mandatory ESP
# partition of reasonable size is created in addition to the root partition.
# Also a legacy MBR will be present.
# For "none", no partition table is created. Enabling `installBootLoader`
# most likely fails as GRUB will probably refuse to install.
partitionTableType ? "legacy"
Expand All @@ -43,7 +54,7 @@
format ? "raw"
}:

assert partitionTableType == "legacy" || partitionTableType == "efi" || partitionTableType == "none";
assert partitionTableType == "legacy" || partitionTableType == "efi" || partitionTableType == "hybrid" || partitionTableType == "none";
# We use -E offset=X below, which is only supported by e2fsprogs
assert partitionTableType != "none" -> fsType == "ext4";

Expand All @@ -65,6 +76,7 @@ let format' = format; in let
rootPartition = { # switch-case
legacy = "1";
efi = "2";
hybrid = "3";
}.${partitionTableType};

partitionDiskScript = { # switch-case
Expand All @@ -76,9 +88,18 @@ let format' = format; in let
efi = ''
parted --script $diskImage -- \
mklabel gpt \
mkpart ESP fat32 8MiB 256MiB \
mkpart ESP fat32 8MiB ${bootSize} \
set 1 boot on \
mkpart primary ext4 256MiB -1
mkpart primary ext4 ${bootSize} -1
'';
hybrid = ''
parted --script $diskImage -- \
mklabel gpt \
mkpart ESP fat32 8MiB ${bootSize} \
set 1 boot on \
mkpart no-fs 0 1024KiB \
set 2 bios_grub on \
mkpart primary ext4 ${bootSize} -1
'';
none = "";
}.${partitionTableType};
Expand Down Expand Up @@ -129,19 +150,6 @@ let format' = format; in let
}

mkdir $out
diskImage=nixos.raw
truncate -s ${toString diskSize}M $diskImage

${partitionDiskScript}

${if partitionTableType != "none" then ''
# Get start & length of the root partition in sectors to $START and $SECTORS.
eval $(partx $diskImage -o START,SECTORS --nr ${rootPartition} --pairs)

mkfs.${fsType} -F -L ${label} $diskImage -E offset=$(sectorsToBytes $START) $(sectorsToKilobytes $SECTORS)K
'' else ''
mkfs.${fsType} -F -L ${label} $diskImage
''}

root="$PWD/root"
mkdir -p $root
Expand Down Expand Up @@ -186,6 +194,31 @@ let format' = format; in let
nixos-install --root $root --no-bootloader --no-root-passwd \
--system ${config.system.build.toplevel} --channel ${channelSources} --substituters ""

diskImage=nixos.raw

${if diskSize == "auto" then ''
${if partitionTableType == "efi" || partitionTableType == "hybrid" then ''
additionalSpace=$(( ($(numfmt --from=iec '${additionalSpace}') + $(numfmt --from=iec '${bootSize}')) / 1000 ))
'' else ''
additionalSpace=$(( $(numfmt --from=iec '${additionalSpace}') / 1000 ))
''}
diskSize=$(( $(set -- $(du -d0 $root); echo "$1") + $additionalSpace ))
truncate -s "$diskSize"K $diskImage
'' else ''
truncate -s ${toString diskSize}M $diskImage
''}

${partitionDiskScript}

${if partitionTableType != "none" then ''
# Get start & length of the root partition in sectors to $START and $SECTORS.
eval $(partx $diskImage -o START,SECTORS --nr ${rootPartition} --pairs)

mkfs.${fsType} -F -L ${label} $diskImage -E offset=$(sectorsToBytes $START) $(sectorsToKilobytes $SECTORS)K
'' else ''
mkfs.${fsType} -F -L ${label} $diskImage
''}

echo "copying staging root to image..."
cptofs -p ${optionalString (partitionTableType != "none") "-P ${rootPartition}"} -t ${fsType} -i $diskImage $root/* /
'';
Expand Down Expand Up @@ -219,7 +252,7 @@ in pkgs.vmTools.runInLinuxVM (

# Create the ESP and mount it. Unlike e2fsprogs, mkfs.vfat doesn't support an
# '-E offset=X' option, so we can't do this outside the VM.
${optionalString (partitionTableType == "efi") ''
${optionalString (partitionTableType == "efi" || partitionTableType == "hybrid") ''
mkdir -p /mnt/boot
mkfs.vfat -n ESP /dev/vda1
mount /dev/vda1 /mnt/boot
Expand Down