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
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shell
}
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shell()
{
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# see https://busybox.net/FAQ.html#job_control
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setsid sh -c "exec sh <> /dev/${console:-tty1} 2>&1" || sh
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}
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findfs()
{
count=0; device=
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case "${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##*=}"
;;
esac
# avoid race condition
while [ ! -e "$device" ]; do
sleep 1; : $(( count += 1 ))
[ "$count" = 30 ] && {
panic "failed to lookup partition"
break
}
done || :
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}
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prepare_environment()
{
. /etc/tinyramfs/config
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export \
LANG=C \
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PS1="# " \
LC_ALL=C \
TERM=linux \
HOME=/root \
SHELL=/bin/sh \
OLD_IFS="$IFS" \
PATH=/bin:/sbin:/usr/bin:/usr/sbin
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# fix for ubase mount
: > /etc/fstab
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mount -t proc -o nosuid,noexec,nodev proc /proc
mount -t sysfs -o nosuid,noexec,nodev sys /sys
mount -t tmpfs -o nosuid,nodev,mode=0755 run /run
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mount -t devtmpfs -o nosuid,noexec,mode=0755 dev /dev
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mkdir -p \
/run/cryptsetup \
/run/lock \
/run/lvm
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ln -s /proc/self/fd /dev/fd
ln -s fd/0 /dev/stdin
ln -s fd/1 /dev/stdout
ln -s fd/2 /dev/stderr
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trap panic EXIT
[ "$modules" ] || return 0
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"
;;
ro | rw)
rorw="-o $line"
;;
*.*)
# TODO implement backward compatibilty with dracut, mkinitcpio, etc
: no operation
;;
*=*)
export "$line" || :
;;
*)
export "${line}=1" || :
;;
esac; done
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}
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setup_devmgr()
{
[ "$break" = devmgr ] && { print "break before setup_devmgr()"; shell; }
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case "$devmgr" in
udev)
udevd -dN never
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udevadm trigger -c add -t subsystems
udevadm trigger -c add -t devices
udevadm settle
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;;
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mdev)
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mdev -df 2> /dev/null & mdev_pid="$!"
mdev -s
[ "$monolith" = 1 ] && return 0
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# TODO maybe replace sort using while-read loop
# while-read can cause slowdown, so why i'm unsure
set -- $(find /sys -name modalias -type f -exec sort -u {} +)
modprobe -a "$@" 2> /dev/null || :
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;;
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mdevd)
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mdevd 2> /dev/null & mdevd_pid="$!"
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mdevd-coldplug
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;;
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esac
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}
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unlock_luks()
{
[ "$break" = luks ] && { print "break before unlock_luks()"; shell; }
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{ IFS=,; set -- $luks_opts; IFS="$OLD_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()"; shell; }
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{ IFS=,; set -- $lvm_opts; IFS="$OLD_IFS"; }
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 $@
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fi
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}
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mount_root()
{
[ "$break" = root ] && { print "break before mount_root()"; shell; }
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findfs "$root"
set -- \
"${root_type:+-t $root_type}" \
"${rorw:--o ro}${root_opts:+,$root_opts}" \
"$device" "/mnt/root"
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mount $@ || panic "failed to mount root"
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}
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cleanup()
{
[ "$break" = cleanup ] && { print "break before cleanup()"; shell; }
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case "$devmgr" in
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udev) udevadm control -e ;;
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mdev) kill "$mdev_pid" ;;
mdevd) kill "$mdevd_pid" ;;
esac
# temporary workaround until util-linux release a new version
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# see https://github.com/karelzak/util-linux/issues/997
for dir in /run /dev /sys /proc; do
mount -o move "$dir" "/mnt/root/${dir}" ||
mount --move "$dir" "/mnt/root/${dir}"
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done
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}
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boot_system()
{
[ "$break" = boot ] && { print "break before boot_system()"; shell; }
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set -- "/mnt/root" "${init:-/sbin/init}"
exec switch_root $@ 2> /dev/null || panic "failed to boot system"
}
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# int main()
{
prepare_environment
parse_cmdline
setup_devmgr
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# trigger lvm twice to handle both LUKS on LVM and LVM on LUKS
[ "$lvm" = 1 ] && trigger_lvm
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[ "$luks" = 1 ] && unlock_luks
[ "$lvm" = 1 ] && trigger_lvm
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mount_root
cleanup
boot_system
}