shrink-ogn-rpi

#!/bin/bash

########################## Users settings, adapt to your needs

DEV="/dev/sdb"			# Sdcard device
VFAT_TRAILING_SIZE=200		# in MiB
EXT_TRAILING_SIZE=50		# in MiB.
INRAM="N"			# work on TMPFS, more efficient. Need TMPFS_SIZE of free memory. use "Y/N".
TMPFS_SIZE="3g"			# Amount of Ram used in tmpfs. Used only when INRAM="Y"
CLEAN="Y"			# clean every temporary files and unmount working fs. use "Y/N"

########################## Script start, do not modified

errors=()
[[ $(whoami) =~ "root" ]] || errors+=("script must be run as root")
which parted >/dev/null || errors+=("parted is not installed")
which fallocate >/dev/null || errors+=("fallocate is not installed")
[[ -b $DEV ]] || errors+=("sdcard not found")
if [[ -b $DEV ]] ; then
	part1=$(lsblk $DEV"1" -o FSTYPE | tail -n1)
	part2=$(lsblk $DEV"2" -o FSTYPE | tail -n1)
	[[ $part1 == "vfat" ]] && [[ $part2 == "ext4" ]] || errors+=($DEV": sdcard wrong parts") 
fi

if [[ !${#errors[@]} -eq 0 ]]; then
	echo 
	echo "#########ERRORS FOUND#########"
	for error in "${errors[@]}"; do
		echo "#-> "$error	
	done
	echo
	exit 1
fi

SCRIPT=`realpath $0`
SCRIPTPATH=`dirname $SCRIPT`
cd $SCRIPTPATH

mkdir -p ./tmpfsd ./sdcard/boot ./sdcard/rfs
if [[ "$INRAM" == "Y" ]] ; then
	grep -qs 'tmpfsd ' /proc/mounts || $(mount -t tmpfs -o size=$TMPFS_SIZE tmpfs ./tmpfsd)
fi
mkdir -p ./tmpfsd/boot ./tmpfsd/rfs

echo "#1: mounting "$DEV" file systems"
grep -qs 'sdcard/boot ' /proc/mounts || $(mount -t vfat -o ro $DEV"1" ./sdcard/boot) || exit 1
grep -qs 'sdcard/rfs ' /proc/mounts || $(mount -t ext4 -o ro $DEV"2" ./sdcard/rfs)   || exit 1

echo "#2: calculate partitions size"
vfat_b=$(du -sb ./sdcard/boot | cut -f1)
vfat_bt=$((vfat_b+(VFAT_TRAILING_SIZE+3)*1024**2))	
# using one megabyte boundaries for alignment
vfat_fstart=4194304
vfat_btm=$((vfat_bt%1048576))	
vfat_fsend=$((vfat_fstart+vfat_bt+1048576-vfat_btm-1))

ext_b=$(du -sb ./sdcard/rfs | cut -f1)
ext_bt=$((ext_b+(EXT_TRAILING_SIZE+136)*1024**2))
ext_inode=$((ext_bt/16384))*256	# by default one inode for 16384 Bytes (16 ko)
ext_reserve=$((1024*4096))	# 1024 blocks reserved (will be fix with tune2fs)
ext_btt=$((ext_bt+ext_inode+ext_reserve))
ext_bttm=$((ext_btt%1048576))	# use one megabyte boundaries for alignment
ext_fstart=$((vfat_fsend+1))
ext_fsend=$((ext_fstart+ext_btt+1048576-ext_bttm-1))
img_size=$((ext_fsend+1))

echo "#3: create & partitioning img"
rm -f ./tmpfsd/img
fallocate -l $img_size ./tmpfsd/img || exit 1
loopd="$(losetup -f --show ./tmpfsd/img)"
parted --script $loopd unit B mklabel msdos \
	mkpart primary fat32 $vfat_fstart $vfat_fsend \
	mkpart primary ext4 $ext_fstart $ext_fsend

echo "#4: create file system"
mkfs.vfat -F 32 $loopd"p1" >/dev/null 2>&1
fatlabel $loopd"p1" boot > /dev/null 2>&1
mkfs.ext4 -q $loopd"p2"
tune2fs -L rfs -f -r 1024 $loopd"p2" >/dev/null 2>&1   # reserved 1024 blocks

echo "#5: poupulate file system"
mount $loopd"p1" ./tmpfsd/boot
mount $loopd"p2" ./tmpfsd/rfs
cp -a ./sdcard/boot/. ./tmpfsd/boot/
cp -a ./sdcard/rfs/. ./tmpfsd/rfs/

echo "#6: patching PARTUUID"
PARTUUID=$(blkid -o value $loopd | head -n1)
sed -i "s/PARTUUID=.*-0/PARTUUID=$PARTUUID-0/" ./tmpfsd/boot/cmdline.txt
sed -i "s/PARTUUID=.*-0/PARTUUID=$PARTUUID-0/" ./tmpfsd/rfs/etc/fstab

if [[ "$CLEAN" == "Y" ]]; then
	echo "#7: cleaning"
	umount ./tmpfsd/boot
	umount ./tmpfsd/rfs
	losetup -d $loopd 
	rm -rf ./tmpfsd/boot ./tmpfsd/rfs
	umount ./sdcard/boot
	umount ./sdcard/rfs
	rm -rf sdcard
fi
echo "#END: image in "$SCRIPTPATH"/tmpfsd/img"