tinyramfs/init

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#!/bin/sh -ef
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#
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# tiny init
#
# word splitting is safe by design
# shellcheck disable=2068,2046,2086
#
# false positive
# shellcheck disable=2154,2163,1091
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print()
{
printf "%b %s\n" "${2:-"\033[1;37m>>\033[m"}" "$1"
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}
panic()
{
print "${1:-unexpected error occurred}" \
"\033[1;31m!!\033[m" >&2; sh
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}
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findfs()
{
count=0; device=
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case "${1%%=*}" in
/dev/*) device="$1" ;;
UUID) device="/dev/disk/by-uuid/${1##*=}" ;;
LABEL) device="/dev/disk/by-label/${1##*=}" ;;
PARTUUID) device="/dev/disk/by-partuuid/${1##*=}" ;;
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esac
# prevent race condition
while [ ! -e "$device" ]; do sleep 1
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[ "$(( count += 1 ))" != 30 ] || {
panic "failed to lookup partition"
break
}
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done
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}
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prepare_environment()
{
. /etc/tinyramfs/config
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export \
PATH=/bin TERM=linux SHELL=/bin/sh \
LANG=C LC_ALL=C PS1="# " HOME=/root \
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mount -t proc -o nosuid,noexec,nodev proc /proc
mount -t sysfs -o nosuid,noexec,nodev sys /sys
mount -t tmpfs -o nosuid,nodev,mode=0755 run /run
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mount -t devtmpfs -o nosuid,noexec,mode=0755 dev /dev
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mkdir -p \
/run/cryptsetup \
/run/lock \
/run/lvm
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ln -s /proc/self/fd /dev/fd
ln -s fd/0 /dev/stdin
ln -s fd/1 /dev/stdout
ln -s fd/2 /dev/stderr
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trap panic EXIT
[ ! "$modules" ] || modprobe -a "$modules"
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}
parse_cmdline()
{
read -r cmdline < /proc/cmdline
for line in $cmdline; do case "$line" in
debug | debug=1) set -x ;;
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rootfstype=*) root_type="${line##*=}" ;;
rootflags=*) root_opts="${line##*=}" ;;
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ro | rw) rorw="-o $line" ;;
--) init_args="${cmdline##*--}"; break ;;
*=*) command export "$line" ;;
*) command export "${line}=1" ;;
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esac 2> /dev/null || continue; done
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}
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setup_devmgr()
{
[ "$break" = devmgr ] && { print "break before setup_devmgr()"; sh; }
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case "$devmgr" in
udev)
udevd -N never & devmgr_pid="$!"
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udevadm trigger -c add -t subsystems
udevadm trigger -c add -t devices
udevadm settle
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;;
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mdev)
mdev -s
mdev -df & devmgr_pid="$!"
[ "$monolith" = 1 ] && return 0
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find /sys/devices -name uevent |
while read -r uevent; do
printf add > "$uevent"
done
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;;
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mdevd)
mdevd & devmgr_pid="$!"
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mdevd-coldplug
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;;
esac 2> /dev/null
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}
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unlock_luks()
{
[ "$break" = luks ] && { print "break before unlock_luks()"; sh; }
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{ IFS=,; set -- $luks_opts; unset IFS; }
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for opt; do case "$opt" in
discard | discard=1) luks_discard="--allow-discards" ;;
header=*) luks_header="--${opt}" ;;
name=*) luks_name="${opt##*=}" ;;
key=*) luks_key="-d ${opt##*=}" ;;
esac; done
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findfs "$luks_root"
set -- \
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"$luks_key" "$luks_header" "$luks_discard" \
"$device" "${luks_name:-luks-${device##*/}}"
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cryptsetup open $@ || panic "failed to unlock LUKS"
}
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trigger_lvm()
{
[ "$break" = lvm ] && { print "break before trigger_lvm()"; sh; }
{ IFS=,; set -- $lvm_opts; unset IFS; }
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for opt; do case "$opt" in
discard | discard=1) lvm_discard="--config=devices{issue_discards=1}" ;;
config=0) : > /etc/lvm/lvm.conf ;;
group=*) lvm_group="${opt##*=}" ;;
name=*) lvm_name="/${opt##*=}" ;;
tag=*) lvm_tag="@${opt##*=}" ;;
esac; done
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set -- "--sysinit" "-qq" "-aay" "$lvm_discard"
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if [ "$lvm_group" ] && [ "$lvm_name" ]; then
lvm lvchange $@ "${lvm_group}${lvm_name}"
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elif [ "$lvm_group" ]; then
lvm vgchange $@ "$lvm_group"
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elif [ "$lvm_tag" ]; then
lvm lvchange $@ "$lvm_tag"
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else
lvm vgchange $@
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fi || panic "failed to trigger LVM"
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}
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mount_root()
{
[ "$break" = root ] && { print "break before mount_root()"; sh; }
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findfs "$root"
set -- \
"${rorw:--o ro}${root_opts:+,$root_opts}" \
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"${root_type:+-t $root_type}" "$device" "/mnt/root"
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mount $@ || panic "failed to mount root"
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}
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boot_system()
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{
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[ "$break" = boot ] && { print "break before boot_system()"; sh; }
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kill "$devmgr_pid"
# temporary workaround until util-linux release a new version
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# see https://github.com/karelzak/util-linux/issues/997
for dir in run dev sys proc; do
mount -o move "$dir" "/mnt/root/${dir}" ||
mount --move "$dir" "/mnt/root/${dir}"
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done
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set -- \
"/mnt/root" "${init:-/sbin/init}" "$init_args"
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exec switch_root $@ || panic "failed to boot system"
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}
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# int main()
{
prepare_environment
parse_cmdline
setup_devmgr
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# trigger lvm twice to handle both LUKS on LVM and LVM on LUKS
[ "$lvm" = 1 ] && trigger_lvm
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[ "$luks" = 1 ] && unlock_luks
[ "$lvm" = 1 ] && trigger_lvm
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mount_root
boot_system
}