add grub support

Signed-off-by: Adphi <philippe.adrien.nousse@gmail.com>

templates/alpine.Dockerfile

@@ -36,3 +36,7 @@ RUN apk add --no-cache cryptsetup && \
     echo "features=\"${features} cryptsetup\"" > /etc/mkinitfs/mkinitfs.conf && \
     mkinitfs $(ls /lib/modules)
 {{- end }}
+
+{{- if .Grub }} \
+RUN apk add --no-cache grub grub-bios
+{{- end }}

templates/centos.Dockerfile

@@ -11,6 +11,9 @@ RUN yum install -y \
     kernel \
     systemd \
     NetworkManager \
+{{- if .Grub }}
+    grub2 \
+{{- end }}
     e2fsprogs \
     sudo && \
     systemctl enable NetworkManager && \

templates/debian.Dockerfile

@@ -9,6 +9,9 @@ RUN apt-get -y update && \
 RUN DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
       systemd-sysv \
       systemd \
+    {{- if .Grub }}
+      grub2 \
+    {{- end }}
       dbus \
       iproute2 \
       isc-dhcp-client \

templates/ubuntu.Dockerfile

@@ -8,6 +8,9 @@ RUN apt-get update -y && \
   initramfs-tools \
   systemd-sysv \
   systemd \
+{{- if .Grub }}
+  grub2 \
+{{- end }}
   dbus \
   isc-dhcp-client \
   iproute2 \