#!/bin/bash
#
#   pacman-cage
#

myver='3.0'

dbroot=/var/lib/pacman
pacmandb=${dbroot}.db

tmp_mnt_point=/mnt/tmp-pacman # temporary mount point
lck_file=/tmp/pacman.lck      # lock file
old_pacsums=/tmp/pacsums.old  # old pacsums
new_pacsums=/tmp/pacsums.new  # new pacsums


usage() { echo -e "pacman-cage $myver\nusage: $0 [pacman_db_root]\n\npacman-cage creates a loopbacked filesystem in a contigious file.\nThis will give better response times when using pacman\n"; }
die() { echo "pacman-cage: $*" >&2; exit 1; }

[[ "$1" != "" ]] && dbroot=$1 && [[ "$1" == "-h" || "$1" == "--h" || "$1" == "--help" || "$1" == "-help" || "$1" == "-?" ]] && usage && exit 2

[[ "$EUID" != 0 ]] && die "You must be root to cage the database"
[[ -f $lck_file ]] && die "Pacman lockfile $lck_file was found.  Cannot run while pacman is running." # make sure pacman isn't running
[[ -f $pacmandb ]] && die "$pacmandb already exists!." # make sure pacman.db hasnt already been made
[[ ! -d $dbroot ]] && die "$dbroot does not exist or is not a directory"


# don't let pacman run while we do this
touch $lck_file && echo "touched $lck_file: don't let pacman run while we do this"

 
# step 1: sum the old db
echo "==> md5sum'ing the old database..."
find $dbroot -type f | sort | xargs md5sum >$old_pacsums


echo "==> creating pacman.db loopback file..."
dd if=/dev/zero of=$pacmandb bs=1M count=150 #> /dev/null 2>&1


echo "==> creating ext4 -O dir_index -b 1024 -m 0 on $pacmandb..."
yes | mkfs.ext4 -O dir_index -b 1024 -m 0 $pacmandb #> /dev/null 2>&1

       
echo "==> creating temporary mount point $tmp_mnt_point.."
mkdir -v $tmp_mnt_point


echo "==> mounting pacman.db to temporary mount point..."
mount -v -o loop $pacmandb $tmp_mnt_point


echo "==> copying pacman database to temporary mount point..."
cp -v -a ${dbroot}/. $tmp_mnt_point


echo "==> unmounting temporary mount point..."
umount -v $tmp_mnt_point


echo "==> removing temporary mount point..."
rmdir -v $tmp_mnt_point

       
echo "==> moving old ${dbroot} to $dbroot_bak..."
mv -v ${dbroot} $dbroot_bak

       
echo "==> createing new pacman db mount point @ $dbroot..."
mkdir -v $dbroot


echo "==> Mounting new pacman db..."
mount -v -o loop $pacmandb $dbroot


echo "==> md5sum'ing the new database..."
find $dbroot -type f | sort | xargs md5sum >$new_pacsums


echo "==> checking integrity..."
diff $old_pacsums $new_pacsums >/dev/null 2>&1
if [ $? -ne 0 ]; then
        echo "# failed, move the old one back into place"
        umount -v $dbroot
        rm -vf $pacmandb
        mv -v $dbroot.bak $dbroot
        rm -vf $lck_file
        die "integrity check FAILED, reverting to old database"
fi

echo "==> Updating /etc/fstab to reflect changes..."
echo "$pacmandb $dbroot ext4 loop,defaults 0 0" | tee -a /etc/fstab
 
rm -vf $lck_file $old_pacsums $new_pacsums
 
 
 
echo -e "\nFinished.  Your pacman database has been caged!.  May the speedy pacman be with you.\n"

exit 0