Prepare switch from legacy network interfaces to systemd-networkd

By default grml-debootstrap used the host /etc/network/interfaces file
to configure the network of the guest system. We now provide a
systemd-networkd configuration enabling DHCP on all network devices next
to the legacy /etc/network/interfaces which only enables DHCP on eth0
(which does not work when using the predictable devices names).

If no networking option is given, this will be the new default.

NOTE: systemd-networkd is currently not enabled by default.

grml-debootstrap

@@ -79,6 +79,7 @@ MNTPOINT="/mnt/debootstrap.$$"
 [ -n "$TIMEZONE" ] || TIMEZONE='Europe/Vienna'
 [ -n "$TUNE2FS" ] || TUNE2FS='tune2fs -c0 -i0'
 [ -n "$UPGRADE_SYSTEM" ] || UPGRADE_SYSTEM='yes'
+[ -n "$USE_DEFAULT_INTERFACES" ] || USE_DEFAULT_INTERFACES="true"
 [ -n "$VMSIZE" ] || VMSIZE="2G"
 
 # inside the chroot system locales might not be available, so use minimum:
@@ -140,11 +141,9 @@ Configuration options:
       --nopackages         Skip installation of packages defined in
                              /etc/debootstrap/packages
       --nokernel           Skip installation of default kernel images.
-      --nointerfaces       Do not copy /etc/network/interfaces from host system
-                           to target system.
-                           (This option is automatically enabled when using --vmfile.)
-      --defaultinterfaces  Install a default /etc/network/interfaces file (enabling
-                           DHCP for eth0) instead of taking over config from host system.
+      --nointerfaces       Skip installation of default network configuration.
+      --defaultinterfaces  Install a default /etc/systemd/network/80-dhcp.network file
+                           (enabling DHCP for all network devices). (default)
       --debconf <file>     Pre-seed packages using specified pre-seed db file.
       --grmlrepos          Enable Grml's Debian repository (deb.grml.org).
       --backportrepos      Enable Debian's backports repository (backports.debian.org).
@@ -441,10 +440,10 @@ while :; do
   --password)          # Use specified password as password for user root
     shift; _opt_password="$1"
     ;;
-  --defaultinterfaces) # Install default /etc/network/interfaces
+  --defaultinterfaces) # Install a default /etc/systemd/network/80-dhcp.network file
     _opt_defaultinterfaces=T
     ;;
-  --nointerfaces)      # Skip installation of /etc/network/interfaces
+  --nointerfaces)      # Skip installation of default network configuration.
     _opt_nointerfaces=T
     ;;
   --nokernel)          # Skip installation of default kernel images
@@ -1673,6 +1672,16 @@ preparechroot() {
   [ -d "${CONFFILES}"/var   ] && cp $VERBOSE -a -L "${CONFFILES}"/var/*   "${MNTPOINT}"/var/
 
   # network setup
+
+  # systemd-networkd
+  DEFAULT_SYSTEMD_NETWORKD="# /etc/systemd/network/80-dhcp.network - generated by grml-debootstrap
+[Match]
+Name=en*
+
+[Network]
+DHCP=yes
+"
+  # legacy network interfaces
   DEFAULT_INTERFACES="# /etc/network/interfaces - generated by grml-debootstrap
 
 # Include files from /etc/network/interfaces.d when using
@@ -1687,30 +1696,20 @@ iface eth0 inet dhcp
 "
 
   if [ -n "$NOINTERFACES" ] ; then
-    einfo "Not installing /etc/network/interfaces as requested via --nointerfaces option" ; eend 0
+    einfo "Not installing /etc/systemd/network/80-dhcp.network as requested via --nointerfaces option"
+    eend 0
   elif [ -n "$USE_DEFAULT_INTERFACES" ] ; then
-    einfo "Installing default /etc/network/interfaces as requested via --defaultinterfaces options."
+    einfo "Installing default /etc/systemd/network/80-dhcp.network as requested via --defaultinterfaces options."
+    echo "$DEFAULT_SYSTEMD_NETWORKD" > "${MNTPOINT}/etc/systemd/network/80-dhcp.network"
     echo "$DEFAULT_INTERFACES" > "${MNTPOINT}/etc/network/interfaces"
     eend $?
   elif [ -n "$VIRTUAL" ] ; then
-    einfo "Setting up Virtual Machine, installing default /etc/network/interfaces"
-    echo "$DEFAULT_INTERFACES" > "${MNTPOINT}/etc/network/interfaces"
-    eend $?
-  elif [ -r /etc/network/interfaces ] ; then
-    einfo "Copying /etc/network/interfaces from host to target system"
-    cp $VERBOSE /etc/network/interfaces "${MNTPOINT}/etc/network/interfaces"
-    eend $?
-  else
-    ewarn "Couldn't read /etc/network/interfaces, installing default /etc/network/interfaces"
+    einfo "Setting up Virtual Machine, installing default /etc/systemd/network/80-dhcp.network"
+    echo "$DEFAULT_SYSTEMD_NETWORKD" > "${MNTPOINT}/etc/systemd/80-dhcp.network"
     echo "$DEFAULT_INTERFACES" > "${MNTPOINT}/etc/network/interfaces"
     eend $?
   fi
 
-  # install config file providing some example entries
-  if [ -r /etc/network/interfaces.examples ] && [ ! -r "$MNTPOINT/etc/network/interfaces.examples" ] ; then
-     cp /etc/network/interfaces.examples "$MNTPOINT/etc/network/interfaces.examples"
-  fi
-
   eend 0
 }
 # }}}