non-interactive debian/ubuntu upgrade

apt-upgrade.sh

#! /bin/sh

PATH=/usr/sbin:/sbin:/usr/bin:/bin

cat <<EOF > /etc/apt/apt.conf.noninteractive
APT::Get::Assume-Yes "true";
APT::Get::Show-Upgraded "true";
APT::Quiet "true";
DPkg::Options {"--force-confmiss";"--force-confold"};
DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt";};
Dir::Etc::SourceList "/etc/apt/sources.list";
APT::ExtractTemplates::TempDir "/tmp";
EOF

if [ ! "`apt-get -q update | grep ^Fetched`" ]
then
  exit 0
fi

# Packages updated: do an upgrade
export DEBIAN_FRONTEND=noninteractive
export DEBIAN_PRIORITY=critical 
/usr/bin/apt-get --config-file /etc/apt/apt.conf.noninteractive -y --force-yes upgrade