nixos-installer/lib/setup-scripts/disk.sh

##
# Disk Partitioning and Formatting
##

declare-flag install-system skip-formatting "" "Skip partitioning, formatting, and their post-commands. Instead, assume that all required disks/images/zpools are correctly partitioned/formatted, and simply (unlock/import and) mount them. This is useful to skip the destruktive part of the installation, but still do the (largely idempotent) part of copying and linking the current system generation and installing the bootloader -- i.e, repair an installation."

## Prepares the disks of the target system for the copying of files.
function do-disk-setup { # 1: diskPaths

    ensure-disks "$1" || return
    prompt-for-user-passwords || return

    export mnt=/tmp/nixos-install-@{config.networking.hostName} && mkdir -p "$mnt" && prepend_trap "rmdir $mnt" EXIT || return # »mnt=/run/user/0/...« would be more appropriate, but »nixos-install« does not like the »700« permissions on »/run/user/0«

    if [[ ${args[skip-formatting]:-} ]] ; then
        if [[ @{config.setup.keystore.enable} ]] ; then
            mount-keystore-luks-primary || return
        else
            populate-keystore || return # (this may be insufficient)
        fi
        open-luks-layers || return
        if [[ $(LC_ALL=C type -t import-zpools) == function ]] ; then import-zpools $mnt || return ; fi
    else
        populate-keystore || return
        partition-disks || return
        create-luks-layers || return
        open-luks-layers || return
        # other block layers would go here too (but figuring out their dependencies would be difficult)
        run-hook-script 'Post Partitioning' @{config.installer.commands.postPartition!writeText.postPartitionCommands} || return

        format-partitions || return
        if [[ $(LC_ALL=C type -t create-zpools) == function ]] ; then create-zpools $mnt || return ; fi
        run-hook-script 'Post Formatting' @{config.installer.commands.postFormat!writeText.postFormatCommands} || return
    fi

    fix-grub-install || return

    prepend_trap "unmount-system $mnt" EXIT && mount-system $mnt || return
    run-hook-script 'Post Mounting' @{config.installer.commands.postMount!writeText.postMountCommands} || return
}

# Notes on segmentation and alignment:
# * Both fdisk and gdisk report start and end in 0-indexed sectors from the start of the block device.
# * (fdisk and gdisk have slightly different interfaces, but seem to otherwise be mostly equivalent, (fdisk used to not understand GPT).)
# * The MBR sits only in the first sector, a GPT additionally requires next 33 (34 total) and the (absolute) last 33 sectors. At least fdisk won't put partitions in the first 2048 sectors on MBRs.
# * Crappy flash storage (esp. micro SD cards) requires alignment to pretty big sectors for optimal (esp. write) performance. For reasons of inconvenience, vendors don't document the size of those. Not too extensive test with 4 (in 2022 considered to be among the more decent) micro SD cards indicates the magic number to be somewhere between 1 and 4MiB, but it may very well be higher for others.
#     * (source: https://lwn.net/Articles/428584/)
# * So alignment at the default »align=8MiB« actually seems a decent choice.

declare-flag install-system image-owner "" "When using image files, »chown« them to this »owner[:group]« before the installation."

## Parses and expands »diskPaths« to ensure that a disk or image exists for each »config.setup.disks.devices«, creates and loop-mounts images for non-/dev/ paths, and checks whether physical device sizes match.
function ensure-disks { # 1: diskPaths, 2?: skipLosetup

    declare -g -A blockDevs=( ) # this ends up in the caller's scope
    if [[ $1 == */ ]] ; then
        mkdir -p "$1"
        for name in "@{!config.setup.disks.devices[@]}" ; do blockDevs[$name]=${1}${name}.img ; done
    else
        local path ; for path in ${1//:/ } ; do
            local name=${path/=*/} ; if [[ $name != "$path" ]] ; then path=${path/$name=/} ; else name=primary ; fi
            if [[ ${blockDevs[$name]:-} ]] ; then echo "Path for block device $name specified more than once. Duplicate definition: $path" 1>&2 ; \return 1 ; fi
            blockDevs[$name]=$path
        done
    fi

    local name ; for name in "@{!config.setup.disks.devices[@]}" ; do
        if [[ ! @{config.setup.disks.devices!catAttrSets.partitionDuringInstallation[$name]} ]] ; then unset blockDevs[$name] ; continue ; fi
        if [[ ! ${blockDevs[$name]:-} ]] ; then echo "Path for block device $name not provided" 1>&2 ; \return 1 ; fi
        eval 'local -A disk='"@{config.setup.disks.devices[$name]}"
        if [[ ${blockDevs[$name]} != /dev/* ]] ; then
            local outFile=${blockDevs[$name]} &&
            install -m 640 -T /dev/null "$outFile" && truncate -s "${disk[size]}" "$outFile" || return
            if [[ ${args[image-owner]:-} ]] ; then chown "${args[image-owner]}" "$outFile" || return ; fi
            if [[ ${2:-} ]] ; then continue ; fi
            blockDevs[$name]=$( @{native.util-linux}/bin/losetup --show -f "$outFile" ) && prepend_trap "@{native.util-linux}/bin/losetup -d '${blockDevs[$name]}'" EXIT || return
        else
            local size=$( @{native.util-linux}/bin/blockdev --getsize64 "${blockDevs[$name]}" || : ) ; local waste=$(( size - ${disk[size]} ))
            if [[ ! $size ]] ; then echo "Block device $name does not exist at ${blockDevs[$name]}" 1>&2 ; \return 1 ; fi
            if (( waste < 0 )) ; then echo "Block device ${blockDevs[$name]}'s size $size is smaller than the size ${disk[size]} declared for $name" 1>&2 ; \return 1 ; fi
            if (( waste > 0 )) && [[ ! ${disk[allowLarger]:-} ]] ; then echo "Block device ${blockDevs[$name]}'s size $size is bigger than the size ${disk[size]} declared for $name" 1>&2 ; \return 1 ; fi
            if (( waste > 0 )) ; then echo "Wasting $(( waste / 1024))K of ${blockDevs[$name]} due to the size declared for $name (should be ${size}b)" 1>&2 ; fi
            blockDevs[$name]=$( realpath "${blockDevs[$name]}" ) || return
        fi
    done
}


## Partitions the »blockDevs« (matching »config.setup.disks.devices«) to ensure that all specified »config.setup.disks.partitions« exist.
#  Tries to abort if any partition already exists on the host.
function partition-disks {
    local beLoud=/dev/null ; if [[ ${args[debug]:-} ]] ; then beLoud=/dev/stdout ; fi
    local beSilent=/dev/stderr ; if [[ ${args[quiet]:-} ]] ; then beSilent=/dev/null ; fi

    for partDecl in "@{config.setup.disks.partitionList[@]}" ; do
        eval 'local -A part='"$partDecl"
        if [[ -e /dev/disk/by-partlabel/"${part[name]}" ]] && ! is-partition-on-disks /dev/disk/by-partlabel/"${part[name]}" "${blockDevs[@]}" ; then echo "Partition /dev/disk/by-partlabel/${part[name]} already exists on this host and does not reside on one of the target disks ${blockDevs[@]}. Refusing to create another partition with the same partlabel!" 1>&2 ; \return 1 ; fi
    done

    for name in "@{!config.setup.disks.devices[@]}" ; do
        if [[ ! @{config.setup.disks.devices!catAttrSets.partitionDuringInstallation[$name]} ]] ; then continue ; fi
        eval 'local -A disk='"@{config.setup.disks.devices[$name]}"
        if [[ ${disk[serial]:-} ]] ; then
            actual=$( @{native.systemd}/bin/udevadm info --query=property --name="$blockDev" | grep -oP 'ID_SERIAL_SHORT=\K.*' || echo '<none>' )
            if [[ ${disk[serial]} != "$actual" ]] ; then echo "Block device $blockDev's serial ($actual) does not match the serial (${disk[serial]}) declared for ${disk[name]}" 1>&2 ; \return 1 ; fi
        fi
        @{native.util-linux}/bin/blkdiscard -f "${blockDevs[${disk[name]}]}" &>$beLoud || true
        # can (and probably should) restore the backup:
        ( PATH=@{native.gptfdisk}/bin ; ${_set_x:-:} ; sgdisk --zap-all --load-backup=@{config.setup.disks.partitioning}/"${disk[name]}".backup ${disk[allowLarger]:+--move-second-header} "${blockDevs[${disk[name]}]}" >$beLoud 2>$beSilent ) || return
        #partition-disk "${disk[name]}" "${blockDevs[${disk[name]}]}" || return
    done
    @{native.parted}/bin/partprobe "${blockDevs[@]}" &>$beLoud || return
    @{native.systemd}/bin/udevadm settle -t 15 || true # sometimes partitions aren't quite made available yet
}

## Given a declared disk device's »name« and a path to an actual »blockDev« (or image) file, partitions the device as declared in the config.
function partition-disk { # 1: name, 2: blockDev, 3?: devSize
    local name=$1 ; local blockDev=$2
    local beLoud=/dev/null ; if [[ ${args[debug]:-} ]] ; then beLoud=/dev/stdout ; fi
    local beSilent=/dev/stderr ; if [[ ${args[quiet]:-} ]] ; then beSilent=/dev/null ; fi
    eval 'local -A disk='"@{config.setup.disks.devices[$name]}"
    local devSize=${3:-$( @{native.util-linux}/bin/blockdev --getsize64 "$blockDev" )}

    local -a sgdisk=( --zap-all ) # delete existing part tables
    if [[ ${disk[gptOffset]} != 0 ]] ; then
        sgdisk+=( --move-main-table=$(( 2 + ${disk[gptOffset]} )) ) # this is incorrectly documented as --adjust-main-table in the man pages (at least versions 1.05 to 1.09 incl)
        sgdisk+=( --move-backup-table=$(( devSize/${disk[sectorSize]} - 1 - 32 - ${disk[gptOffset]} )) )
    fi
    sgdisk+=( --disk-guid="${disk[guid]}" )

    for partDecl in "@{config.setup.disks.partitionList[@]}" ; do
        eval 'local -A part='"$partDecl"
        if [[ ${part[disk]} != "${disk[name]}" ]] ; then continue ; fi
        if [[ ${part[size]:-} =~ ^[0-9]+%$ ]] ; then
            part[size]=$(( $devSize / 1024 * ${part[size]:0:(-1)} / 100 ))K
        fi
        sgdisk+=(
            --set-alignment="${part[alignment]:-${disk[alignment]}}"
            --new="${part[index]:-0}":"${part[position]}":+"${part[size]:-}"
            --partition-guid=0:"${part[guid]}"
            --typecode=0:"${part[type]}"
            --change-name=0:"${part[name]}"
        )
    done

    if [[ ${disk[mbrParts]:-} ]] ; then
        sgdisk+=( --hybrid "${disk[mbrParts]}" ) # --hybrid: create MBR in addition to GPT; ${disk[mbrParts]}: make these GPT part 1 MBR parts 2[3[4]]
    fi

    ( PATH=@{native.gptfdisk}/bin ; ${_set_x:-:} ; sgdisk "${sgdisk[@]}" "$blockDev" >$ ) || return # running all at once is much faster

    if [[ ${disk[mbrParts]:-} ]] ; then
        printf %s "
            M                                # edit hybrid MBR
            d;1                              # delete parts 1 (GPT)

            # move the selected »mbrParts« to slots 1[2[3]] instead of 2[3[4]] (by re-creating part1 in the last sector, then sorting)
            n;p;1                            # new ; primary ; part1
            $(( ($devSize/${disk[sectorSize]}) - 1)) # start (size 1sec)
            x;f;r                            # expert mode ; fix order ; return
            d;$(( (${#disk[mbrParts]} + 1) / 2 + 1 )) # delete ; part(last)

            # create GPT part (spanning primary GPT area and its padding) as last part
            n;p;4                            # new ; primary ; part4
            1;$(( 33 + ${disk[gptOffset]} )) # start ; end
            t;4;ee                           # type ; part4 ; GPT

            ${disk[extraFDiskCommands]}
            p;w;q                            # print ; write ; quit
        " | @{native.gnused}/bin/sed -E 's/^ *| *(#.*)?$//g' | @{native.gnused}/bin/sed -E 's/\n\n+| *; */\n/g' |
        tee >( [[ ! ${_set_x:-} ]] || ( echo -n '++ ' ; tr $'\n' '|' ; echo ) 1>&2 ; cat >/dev/null ) |
        ( PATH=@{native.util-linux}/bin ; ${_set_x:-:} ; fdisk "$blockDev" &>$beLoud ) || return
    fi
}

## Checks whether a »partition« resides on one of the provided »blockDevs«.
function is-partition-on-disks { # 1: partition, ...: blockDevs
    local partition=$1 ; shift ; local -a blockDevs=( "$@" )
    local blockDev=/dev/$( basename "$( readlink -f /sys/class/block/"$( basename "$( realpath "$partition" )" )"/.. )" ) || return
    [[ ' '"${blockDevs[@]}"' ' == *' '"$blockDev"' '* ]] || return
}

## For each filesystem in »config.fileSystems« whose ».device« is in »/dev/disk/by-partlabel/«, this creates the specified file system on that partition.
function format-partitions {
    local beLoud=/dev/null ; if [[ ${args[debug]:-} ]] ; then beLoud=/dev/stdout ; fi
    local beSilent=/dev/stderr ; if [[ ${args[quiet]:-} ]] ; then beSilent=/dev/null ; fi
    for fsDecl in "@{config.fileSystems[@]}" ; do
        eval 'declare -A fs='"$fsDecl"
        if [[ ${fs[device]} == /dev/disk/by-partlabel/* ]] ; then
            if ! is-partition-on-disks "${fs[device]}" "${blockDevs[@]}" ; then echo "Partition alias ${fs[device]} used by mount ${fs[mountPoint]} does not point at one of the target disks ${blockDevs[@]}" 1>&2 ; \return 1 ; fi
            @{native.util-linux}/bin/wipefs --all "${fs[device]}" >$beLoud 2>$beSilent || return # else mkfs might refuse to replace any previous filesystems
        elif [[ ${fs[device]} == /dev/mapper/* ]] ; then
            if [[ ! @{config.boot.initrd.luks.devices!catAttrSets.device[${fs[device]/'/dev/mapper/'/}]:-} ]] ; then echo "LUKS device ${fs[device]} used by mount ${fs[mountPoint]} does not point at one of the device mappings ${!config.boot.initrd.luks.devices!catAttrSets.device[@]}" 1>&2 ; \return 1 ; fi
        else continue ; fi
        eval 'declare -a formatArgs='"${fs[formatArgs]}"
        ( PATH=@{native.e2fsprogs}/bin:@{native.f2fs-tools}/bin:@{native.xfsprogs}/bin:@{native.dosfstools}/bin:$PATH ; ${_set_x:-:} ; mkfs."${fs[fsType]}" "${formatArgs[@]}" "${fs[device]}" >$beLoud 2>$beSilent ) || [[ $options == *,nofail,* ]] || return
        @{native.parted}/bin/partprobe "${fs[device]}" || true
    done
    for swapDev in "@{config.swapDevices!catAttrs.device[@]}" ; do
        if [[ $swapDev == /dev/disk/by-partlabel/* ]] ; then
            if ! is-partition-on-disks "$swapDev" "${blockDevs[@]}" ; then echo "Partition alias $swapDev used for SWAP does not point at one of the target disks ${blockDevs[@]}" 1>&2 ; \return 1 ; fi
            @{native.util-linux}/bin/wipefs --all "${fs[device]}" >$beLoud 2>$beSilent || return # else mkswap might refuse to replace any previous filesystems
        elif [[ $swapDev == /dev/mapper/* ]] ; then
            if [[ ! @{config.boot.initrd.luks.devices!catAttrSets.device[${swapDev/'/dev/mapper/'/}]:-} ]] ; then echo "LUKS device $swapDev used for SWAP does not point at one of the device mappings @{!config.boot.initrd.luks.devices!catAttrSets.device[@]}" 1>&2 ; \return 1 ; fi
        else continue ; fi
        ( PATH=@{native.util-linux}/bin ; ${_set_x:-:} ; mkswap "$swapDev" >$beLoud 2>$beSilent ) || return
    done
}

## This makes the installation of grub to loop devices shut up, but booting still does not work (no partitions are found). I'm done with GRUB; EXTLINUX works.
#  (This needs to happen before mounting.)
function fix-grub-install {
    if [[ @{config.boot.loader.grub.enable:-} ]] ; then
        if [[ @{config.boot.loader.grub.devices!length:-} != 1 || @{config.boot.loader.grub.mirroredBoots!length:-} != 0 ]] ; then echo "Installation of grub as mirrors or to more than 1 device may not work" 1>&2 ; fi
        for mount in '/boot' '/boot/grub' ; do
            if [[ ! @{config.fileSystems[$mount]:-} ]] ; then continue ; fi
            device=$( eval 'declare -A fs='"@{config.fileSystems[$mount]}" ; echo "${fs[device]}" )
            label=${device/\/dev\/disk\/by-partlabel\//}
            if [[ $label == "$device" || $label == *' '* || ' '@{config.setup.disks.partitions!attrNames[@]}' ' != *' '$label' '* ]] ; then echo "" 1>&2 ; \return 1 ; fi
            bootLoop=$( @{native.util-linux}/bin/losetup --show -f /dev/disk/by-partlabel/$label ) || return ; prepend_trap "@{native.util-linux}/bin/losetup -d $bootLoop" EXIT
            ln -sfT ${bootLoop/\/dev/..\/..} /dev/disk/by-partlabel/$label || return
        done
        #umount $mnt/boot/grub || true ; umount $mnt/boot || true ; mount $mnt/boot || true ; mount $mnt/boot/grub || true
    fi
}

## Mounts all file systems as it would happen during boot, but at path prefix »$mnt« (instead of »/«).
function mount-system {( # 1: mnt, 2?: fstabPath, 3?: allowFail
    # While not generally required for fstab, nixos uses the dependency-sorted »config.system.build.fileSystems« list (instead of plain »builtins.attrValues config.fileSystems«) to generate »/etc/fstab« (provided »config.fileSystems.*.depends« is set correctly, e.g. for overlay mounts).
    # This function depends on the file at »fstabPath« to be sorted like that.

    mnt=$1 ; fstabPath=${2:-"@{config.system.build.toplevel}/etc/fstab"} ; allowFail=${3:-}
    PATH=@{native.e2fsprogs}/bin:@{native.f2fs-tools}/bin:@{native.xfsprogs}/bin:@{native.dosfstools}/bin:$PATH

    # The following is roughly equivalent to: mount --all --fstab "$fstabPath" --target-prefix "$mnt" -o X-mount.mkdir # (but »--target-prefix« does not apply to bind/overlay sources)
    while read -u3 source target type options numbers ; do
        if [[ ! $target || $target == none ]] ; then continue ; fi
        options=,$options, ; options=${options//,ro,/,}

        if ! @{native.util-linux}/bin/mountpoint -q "$mnt"/"$target" ; then (
            mkdir-sticky "$mnt"/"$target" || exit
            [[ $type == tmpfs || $type == auto || $type == */* ]] || @{native.kmod}/bin/modprobe --quiet $type || true # (this does help sometimes)

            if [[ $type == overlay ]] ; then
                options=${options//,workdir=/,workdir=$mnt\/} ; options=${options//,upperdir=/,upperdir=$mnt\/} # Work and upper dirs must be in target.
                workdir=$(  <<<"$options" grep -o -P ',workdir=\K[^,]+'  || true ) ; if [[ $workdir  ]] ; then mkdir-sticky "$workdir"  ; fi
                upperdir=$( <<<"$options" grep -o -P ',upperdir=\K[^,]+' || true ) ; if [[ $upperdir ]] ; then mkdir-sticky "$upperdir" ; fi
                lowerdir=$( <<<"$options" grep -o -P ',lowerdir=\K[^,]+' || true )
                options=${options//,lowerdir=$lowerdir,/,lowerdir=$mnt/${lowerdir//:/:$mnt\/},} ; source=overlay
                # TODO: test the lowerdir stuff
            elif [[ $options =~ ,r?bind, ]] ; then
                if [[ $source == /nix/store/* ]] ; then options=,ro$options ; fi
                source=$mnt/$source ; if [[ ! -e $source ]] ; then mkdir-sticky "$source" || exit ; fi
            fi

            @{native.util-linux}/bin/mount -t $type -o "${options:1:(-1)}" "$source" "$mnt"/"$target" || exit

        ) || [[ $options == *,nofail,* || $allowFail ]] || exit ; fi # (actually, nofail already makes mount fail silently)
    done 3< <( <$fstabPath grep -v '^#' )
)}

## Unmounts all file systems (that would be mounted during boot / by »mount-system«).
function unmount-system { # 1: mnt, 2?: fstabPath
    local mnt=$1 ; local fstabPath=${2:-"@{config.system.build.toplevel}/etc/fstab"}
    while read -u3 source target rest ; do
        if [[ ! $target || $target == none ]] ; then continue ; fi
        if @{native.util-linux}/bin/mountpoint -q "$mnt"/"$target" ; then
            @{native.util-linux}/bin/umount "$mnt"/"$target" || return
        fi
    done 3< <( { <$fstabPath grep -v '^#' ; echo ; } | tac )
}