tried to fix offline repo

don't forget to switch off offline repo when installation is cancelled;
make sure offline repo is used by default if available;
use halifax server as backup if packages are not in offline repo

scripts/linuxparty.sh

@@ -293,7 +293,7 @@ showerr() {
 trap showerr ERR
 
 apt-install() {
-  apt-get install ${APT_ARGS} $@
+  apt-get ${APT_SOURCE_ARG} install ${APT_ARGS} $@
   INSTALLED_PKGS="$INSTALLED_PKGS $@"
 }
 
@@ -401,6 +401,13 @@ else
   fi
 fi
 
+if [ -e /etc/apt/sources.list.d/lipoffline.list ]
+then
+    APT_SOURCE_ARG='-o Dir::Etc::SourceList=/etc/apt/sources.list.d/lipoffline.list'
+else
+    APT_SOURCE_ARG='-o Dir::Etc::SourceList=/etc/apt/sources.list'
+fi
+
 # Paketquellen bereitlegen.
   echo
   echo "Bereitstellung der Paketquellen"
@@ -421,19 +428,23 @@ else
   #echo "Update der Paketquellen aus dem Internet mit 'apt-get update'"
   # Wie sichert man apt-get update ab ?
   # apt-get -o Dir::Etc::SourceList=/etc/apt/sources.list.d/lipoffline.list,Dir::Etc::SourceParts="" update
-  apt-get update
+  apt-get ${APT_SOURCE_ARG} update
 fi
 
 if [ -n "$ASKTOSKIP" ]; then
-  askyesno "Möchtest du an dieser Stelle Aktualisierungen und spezielle Software für dein Studium installieren (empfohlen)?" || exit 0
+  if ! askyesno "Möchtest du an dieser Stelle Aktualisierungen und spezielle Software für dein Studium installieren (empfohlen)?"
+  then
+    bash $MY_DIR/liprepoctl.sh off
+    exit 0
+  fi
 fi
 
 pressenter "Im folgenden werden Aktualisierungen installiert. Dies wird einige Minuten dauern."
 echo "Installiere Updates (hoffentlich vom USB-Repo)"
-apt-get upgrade ${APT_ARGS}
+apt-get ${APT_SOURCE_ARG} upgrade ${APT_ARGS}
 
 echo "Installiere Standard-Programme"
-apt-get install ${APT_ARGS} $(grep '^[^|#]*D[^|]*|' "$MY_DIR/../packages" | cut -d'|' -f 2)
+apt-get ${APT_SOURCE_ARG} install ${APT_ARGS} $(grep '^[^|#]*D[^|]*|' "$MY_DIR/../packages" | cut -d'|' -f 2)
 
 # System absichern
 if askyesno "Netzwerk: Soll die Ubuntu Firewall (ufw/gufw) aktiviert werden ?"

scripts/liprepoctl.sh

@@ -2,6 +2,7 @@
 
 ACTION="$1"
 FILENAME="/etc/apt/sources.list.d/lipoffline.list"
+ONLINEFILENAME="/etc/apt/sources.list.d/liponline.list"
 ACTIVATED=`test -e "$FILENAME"`
 
 . /etc/lsb-release
@@ -12,11 +13,14 @@ function install_repo()
 {
 	echo "# offline repository of the linux install party
 deb [ arch=amd64 trusted=yes ] file://$1/archives-$DIST_CODENAME $DIST_CODENAME lip" > "$FILENAME"
+	echo "deb http://ftp.halifax.rwth-aachen.de/ubuntu/ impish main restricted universe multiverse
+deb http://ftp.halifax.rwth-aachen.de/ubuntu/ impish-security main restricted universe multiverse
+deb http://ftp.halifax.rwth-aachen.de/ubuntu/ impish-updates main restricted universe multiverse" > "$ONLINEFILENAME"
 }
 
 function uninstall_repo()
 {
-	rm -f "$FILENAME"
+	rm -f "$FILENAME" "$ONLINEFILENAME"
 }
 
 case $ACTION in