Safe upgrade of a debian system

debian-safe-upgrade.sh

#!/bin/sh

OLDDIST=lenny
NEWDIST=squeeze

BACKUP_DIR="/var/tmp/backup.$OLDDIST"

echo "+ Create backup directory"
mkdir -p "$BACKUP_DIR"

echo "+ Backup system config directories"
rsync -ac /etc /var/lib/dpkg /var/lib/apt/extended_states "$BACKUP_DIR"
dpkg --get-selections "*" > "$BACKUP_DIR/curr-pkgs.txt"

echo "+ Check aptitude in visual mode and press 'g' [ENTER]"
read
#aptitude

echo "+ Check apt preferences (pinnged packages)"
if [ -e "/etc/apt/preferences" ]; then
        echo "Check that you haven't pinned any packages [ENTER]"
        read
fi

echo "+ Check dpkg audit log"
dpkg --audit
if [ "$?" != "0" ]; then
        echo "Something failed with dpkg --audit ? "
        exit 1
fi

echo "+ Search packages on hold"
#aptitude search "~ahold"
dpkg --get-selections | grep hold > "$BACKUP_DIR/pkgs-on-hold.txt"

if [ "$(grep proposed-updates /etc/apt/sources.list)" != "" ]; then
        echo "***** You should remove proposed-updates from your sources.list"
        exit 2
fi

if [ "$(grep backports /etc/apt/sources.list)" != "" ]; then
        echo "***** Backports is enabled. Remove it."
        exit 3
fi

echo "+ Update the sources.list to point to $NEWDIST [ENTER]"
read

echo "+ Update apt database..."
apt-get update

echo "+ Disk space check..."
apt-get -o APT::Get::Trivial-Only=true dist-upgrade

echo "+ Minimal system upgrade [ENTER]"
read
apt-get upgrade