-eval $(apt-config shell UpdateInterval APT::Periodic::Update-Package-Lists DownloadUpgradeableInterval APT::Periodic::Download-Upgradeable-Packages)
-AutocleanInterval=$DownloadUpgradeableInterval
-eval $(apt-config shell AutocleanInterval APT::Periodic::Autoclean)
+eval $(apt-config shell DownloadUpgradeableInterval APT::Periodic::Download-Upgradeable-Packages)
+
+UnattendedUpgradeInterval=0
+eval $(apt-config shell UnattendedUpgradeInterval APT::Periodic::Unattended-Upgrade)
+
+AutocleanInterval=0
+eval $(apt-config shell AutocleanInterval APT::Periodic::AutocleanInterval)
+
+Cache="${Dir}/${CacheDir}/${CacheArchive}/"
+Back="${Dir}/${CacheDir}/${CacheBackup}/"
+BackX="${Back}${CacheArchive}/"
+for x in $(seq 0 1 $((${BackupLevel}-1))); do
+ eval "Back${x}=${Back}${x}/"
+done
+
+# backup after n-days if archive contents changed.
+# (This uses hardlink to save disk space)
+BACKUP_ARCHIVE_STAMP=/var/lib/apt/periodic/backup-archive-stamp
+if check_stamp $BACKUP_ARCHIVE_STAMP $BackupArchiveInterval; then
+ if [ $({(cd $Cache 2>/dev/null; find . -name "*.deb"); (cd $Back0 2>/dev/null;find . -name "*.deb") ;}| sort|uniq -u|wc -l) -ne 0 ]; then
+ mkdir -p $Back
+ rm -rf $Back$((${BackupLevel}-1))
+ for y in $(seq $((${BackupLevel}-1)) -1 1); do
+ eval BackY=${Back}$y
+ eval BackZ=${Back}$(($y-1))
+ if [ -e $BackZ ]; then mv -f $BackZ $BackY ; fi
+ done
+ cp -la $Cache $Back ; mv -f $BackX $Back0
+ update_stamp $BACKUP_ARCHIVE_STAMP
+ debug_echo "backup with hardlinks. (success)"
+ else