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| | #!/usr/bin/env -S bash --
# SPDX-FileCopyrightText: 2021-2023 Alyssa Ross <hi@alyssa.is>
# SPDX-FileCopyrightText: 2022 Unikie
# SPDX-License-Identifier: EUPL-1.2+
#
# usage: bash make-gpt.sh GPT_PATH PATH:PARTTYPE[:PARTUUID[:PARTLABEL]]...
set -xeuo pipefail
ONE_MiB=1048576
# Prints the number of 1MiB blocks required to store the file named
# $1. We use 1MiB blocks because that's what sfdisk uses for
# alignment. It would be possible to get a slightly smaller image
# using actual normal-sized 512-byte blocks, but it's probably not
# worth it to configure sfdisk to do that.
sizeMiB() {
wc -c "$1" | awk -v ONE_MiB=$ONE_MiB \
'{printf "%d\n", ($1 + ONE_MiB - 1) / ONE_MiB}'
}
# Copies from path $3 into partition number $2 in partition table $1.
fillPartition() {
start="$(sfdisk -J "$1" | jq -r --argjson index "$2" \
'.partitiontable.partitions[$index].start * 512')"
# GNU cat will use copy_file_range(2) if possible, whereas dd
# will always do a userspace copy, which is significantly slower.
lseek -S 1 "$start" cat "$3" 1<>"$1"
}
# Prints the partition path from a PATH:PARTTYPE[:PARTUUID[:PARTLABEL]] string.
partitionPath() {
awk -F: '{print $1}' <<EOF
$1
EOF
}
scriptsDir="$(dirname "$0")"
out="$1"
shift
table="label: gpt"
# Keep 1MiB free at the start, and 1MiB free at the end.
gptBytes=$((ONE_MiB * 2))
for partition; do
if [[ "$partition" =~ :([1-9][0-9]*)MiB$ ]]; then
sizeMiB=${BASH_REMATCH[1]}
partition=${partition%:*}
else
partitionPath=$(partitionPath "$partition")
sizeMiB=$(sizeMiB "$partitionPath")
fi
table+=$'\n'"size=${sizeMiB}MiB,$(awk -f "$scriptsDir/sfdisk-field.awk" -v partition="$partition")"
gptBytes=$((gptBytes + sizeMiB * ONE_MiB))
done
rm -f "$out"
truncate -s "$gptBytes" "$out"
sfdisk --no-reread --no-tell-kernel "$out" <<EOF
$table
EOF
n=0
for partition; do
partitionPath=$(partitionPath "$partition")
fillPartition "$out" "$n" "$partitionPath"
n=$((n + 1))
done
|