#!/bin/bash
# Author: Jeffrey Vandenborne
# Date: November 17, 2011
# TODO: monitor whether snapshot size does the job well enough at <num>gb

# FIX: path is now set
PROFILE_FILES=(/etc/profile)
for pfile in $PROFILE_FILES; do
    [ -f $pfile ] && {
        echo "Set environment variables: $pfile"
        . $pfile || exit 1
    }
done

RSYNC=$(which rsync)
MOUNT=$(which mount)
UMOUNT=$(which umount)
LVCREATE=$(which lvcreate)
LVREMOVE=$(which lvremove)
GREP=$(which egrep)
RSYNC_FLAGS="-a --delete"
BACKUP_DIR=/backup/homes
BDIR_IS_MOUNT=1
BACKUPGROUP=backup
SNAPSHOT_NAME=s_homes_bck
SNAPSHOT_SIZE=16G
VOL_GROUP=system
SNAPSHOT_TARGET=home
SNAPSHOT_DIR=/mnt/snap_home_bck
USERS=$(egrep ^$BACKUPGROUP /etc/group | perl -pe 's/.*://g' | tr ',' ' ')

# Make sure snapsnots are unmounted and removed upon completion of backup
trap "cleanup; echo BACKUP END -- $(date); echo" EXIT
trap "echo 'SIGINT/SIGTERM detected'; cleanup; echo 'TERMINATING -- '$(date); echo; kill -9 $$" SIGINT SIGTERM

# Create snapshot for home volume
create_snapshot() {
    $LVCREATE -L$SNAPSHOT_SIZE -s -n $SNAPSHOT_NAME /dev/$VOL_GROUP/$SNAPSHOT_TARGET
    [ $? -ne 0 ] && return 1

    if [[ ! -d "$SNAPSHOT_DIR" ]]; then
        mkdir "$SNAPSHOT_DIR" 2>/dev/null
        [ $? -ne 0 ] && return 1 || echo "$SNAPSHOT_DIR created!"
    else
        1>&2 echo "Directory $SNAPSHOT_DIR exists, exiting"
        exit 1
    fi

    $MOUNT "/dev/$VOL_GROUP/$SNAPSHOT_NAME" "$SNAPSHOT_DIR"
    return $?
}

# Unmount and remove snapshot
cleanup() {
    echo "Unmounting and removing snapshot volume: $SNAPSHOT_NAME"
    /bin/sync
    $UMOUNT "$SNAPSHOT_DIR"
    $LVREMOVE -f "/dev/$VOL_GROUP/$SNAPSHOT_NAME"
    rmdir "$SNAPSHOT_DIR" 2>/dev/null
}

[ -z "$USERS" ] && exit 0

# Check wether the volume is mounted or not
if [[ $BDIR_IS_MOUNT -eq 1 ]]; then
    if ! $MOUNT | $GREP -q "\W$BACKUP_DIR\W"; then
        1>&2 echo "Volume is not mounted, exiting"
        exit 1
    fi
else
    if [ ! -d $BACKUP_DIR ]; then
        1>&2 echo "Backup dir doesnt exist"
        exit 1
    fi
fi

# Create a snapshot for data efficiency
create_snapshot || {
    echo "Can't create snapshot"
    exit 1
}

echo "BACKUP START: $(date)"
for user in $USERS; do
    [ ! -d $SNAPSHOT_DIR/$user ] && break

    # TODO: read backup exclude files located at $SNAPSHOT_DIR/$user/.backup.exclude
    # Every directory and file mentioned in this file will be ignored by rsync

    echo "BACKUP: $SNAPSHOT_DIR/$user"
    $RSYNC $RSYNC_FLAGS $SNAPSHOT_DIR/$user $BACKUP_DIR
    [ $? -eq 0 ] || echo "Backup for $user failed"
done

exit 0