backupscript.bash

#!/bin/bash
# Backup Script - Matthew Gyurgyik (pyther@pyther.net)
#
# Backup a System using rsync and --link-dest (hard links)
# Backups are stored in a folder called $Year$Month$Day ex. 2010Oct18
#
# Exclude file format:
# /backup/exclude.txt
#  + /etc
#  + /home
#  + /srv
#  - /*
#
# Due to the nature of hard links, only one copy of the file is stored on the
# backup drive.

# Edit These
backupdir="/backup"
mountpoint="/backup"
srcdir="/"
dstdir=$backupdir/$(date +%Y%h%d)
excludeFile="$backupdir/exclude.txt"
lastbackup="$backupdir/last.txt"
rsync_opts=(--archive --delete-excluded --numeric-ids --human-readable "--exclude-from=$excludeFile")

# Root check
if (( $UID != 0 )); then
   echo "This script must be run as root" 1>&2
   exit 1
fi

# Try to mount the drive
# If unsuccessful quit
if mountpoint -q "$mountpoint"; then
    echo "$mountpoint is mounted"
else
    echo "$mountpoint is not mounted"
    if ! mount "$mountpoint"; then
        echo "Error mounting drive... BAILING"
        exit 1
    fi
fi

# Sanity Checks
# if directory exists we don't want to overwrite it
if [[ -d $dstdir ]]; then
    echo "Destination Directory Already Exists!"
    echo "Terminating!"
    exit 1
elif [[ ! -d $srcdir ]]; then
    echo "No source directory"
    exit 1
fi

if [[ -f $lastbackup ]]; then
    read linkdir </backup/last.txt
    rsync_opts+=("--link-dest=$linkdir")
else
    echo "No previous backups found."
fi

echo "Rsync Options: ${rsync_opts[@]}"
echo "Destination Directory: $dstdir"
echo "Linking Directory: $linkdir"

# Make Dest Dir
mkdir -p "$dstdir"

# Lets run the command
# If successful store dest dir into lastbackup (file)
# Else tell the user and exit 1
if /usr/bin/rsync "${rsync_opts[@]}" "$srcdir" "$dstdir"; then
    echo "$dstdir" > "$lastbackup"
else
    echo "Rsync exited with status: $?"
    echo "Backup is considered incomplete."
    exit 1
fi

echo "$(df -h $mountpoint)"

echo "Unmounting Drive"
umount "$mountpoint"

(( "$UID" != "0" )) && { echo "This script must be run as root" >&2; exit 1; }

...
else
printf "%s\n" "$mountpoint is not mounted" "trying to mount.."
mount $mountpoint || { printf "%s\n" "Error mounting drive... BAILING"; exit 1; }
fi
...
if /usr/bin/rsync $rsync_opts $srcdir $dstdir; then
[[ $1 == "full" ]] && echo "$dstdir" > "$lastfull"
echo "$dstdir" > "$lastinc";
else
printf "%s\n" "Rysnc exited with status: $?" "Backup is considered incomplete."
fi

I would also quote all dirs (mountpoint, destdir, etc)
and things like rsync_opts+=" --link-dest="$linkdir
could be rsync_opts+=" --link-dest=$linkdir"

also ls can sort files according to ctime with -c option, so you could get away with having to write a file with the lastinc and/or lastfull , but alternatively do something like head -1 < <(ls -1tc)

I may use this :D