Add VNC support

Dockerfile

@@ -18,12 +18,18 @@ RUN apt-get update && apt-get -y upgrade && \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
-COPY src/*.sh /run/
+# Using a wildcard causes caching problems on some systems
+COPY src/disk.sh /run/
+COPY src/display.sh /run/
+COPY src/entry.sh /run/
+COPY src/install.sh /run/
+COPY src/network.sh /run/
 RUN chmod +x /run/*.sh
 
 VOLUME /storage
 
 EXPOSE 22
+EXPOSE 5900
 
 ENV CPU_CORES "1"
 ENV DISK_SIZE "16G"

docker-compose.yml

@@ -8,6 +8,8 @@ services:
             RAM_SIZE: "512M"            
             DISK_SIZE: "16G"
             BOOT: "https://dl-cdn.alpinelinux.org/alpine/v3.18/releases/x86_64/alpine-standard-3.18.2-x86_64.iso"
+            DISPLAY: "vnc"
+            CONTROL_PORTS: "5900"
         devices:
             - /dev/kvm
             - /dev/vhost-net
@@ -17,5 +19,6 @@ services:
             - NET_ADMIN                       
         ports:
             - 22:22
+            - 5900:5900
         restart: on-failure
         stop_grace_period: 1m

readme.md

@@ -187,6 +187,17 @@ docker run -it --rm -e "BOOT=http://www.example.com/image.iso" --device=/dev/kvm
 
     Please note that even if you don't need DHCP, it's still recommended to enable this feature as it prevents NAT issues and increases performance by using a `macvtap` interface.
 
+  * ### How can I connect with VNC?
+
+    To enable VNC, add the following lines to your compose file:
+
+    ```yaml
+    ports:
+      "5900:5900"
+    environment:
+      DISPLAY: "vnc"
+    ```
+
 [build_url]: https://github.com/qemu-tools/qemu-docker/
 [hub_url]: https://hub.docker.com/r/qemux/qemu-docker/
 [tag_url]: https://hub.docker.com/r/qemux/qemu-docker/tags

src/display.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+set -Eeuo pipefail
+
+# Docker environment variables
+
+: ${DISPLAY:='none'}    # Display type
+
+case "$DISPLAY" in
+  vnc)
+    DISPLAY_OPTS="-nographic -vga std -vnc :0"
+    ;;
+  *)
+    DISPLAY_OPTS="-nographic -display none"
+    ;;
+esac

src/entry.sh

@@ -34,6 +34,7 @@ cd /run
 . install.sh    # Get bootdisk
 . disk.sh       # Initialize disks
 . network.sh    # Initialize network
+. display.sh    # Initialize display
 
 KVM_ERR=""
 KVM_OPTS=""
@@ -55,19 +56,20 @@ else
   KVM_OPTS=",accel=kvm -enable-kvm -cpu host"
 fi
 
-DEF_OPTS="-nographic -nodefaults -display none"
+DEF_OPTS="-nodefaults"
 RAM_OPTS=$(echo "-m ${RAM_SIZE}" | sed 's/MB/M/g;s/GB/G/g;s/TB/T/g')
 CPU_OPTS="-smp ${CPU_CORES},sockets=1,dies=1,cores=${CPU_CORES},threads=1"
 MAC_OPTS="-machine type=q35,usb=off,dump-guest-core=off,hpet=off${KVM_OPTS}"
 SERIAL_OPTS="-serial mon:stdio -device virtio-serial-pci,id=virtio-serial0,bus=pcie.0,addr=0x3"
 EXTRA_OPTS="-device virtio-balloon-pci,id=balloon0 -object rng-random,id=rng0,filename=/dev/urandom -device virtio-rng-pci,rng=rng0"
 
-ARGS="${DEF_OPTS} ${CPU_OPTS} ${RAM_OPTS} ${MAC_OPTS} ${SERIAL_OPTS} ${NET_OPTS} ${DISK_OPTS} ${EXTRA_OPTS} ${ARGUMENTS}"
+ARGS="${DEF_OPTS} ${CPU_OPTS} ${RAM_OPTS} ${MAC_OPTS} ${SERIAL_OPTS} ${NET_OPTS} ${DISK_OPTS} ${DISPLAY_OPTS} ${EXTRA_OPTS} ${ARGUMENTS}"
 ARGS=$(echo "$ARGS" | sed 's/\t/ /g' | tr -s ' ')
 
 trap - ERR
 info "Booting image using ${VERS}..."
 
+
 [[ "${DEBUG}" == [Yy1]* ]] && set -x
 exec qemu-system-x86_64 ${ARGS:+ $ARGS}
 { set +x; } 2>/dev/null

src/network.sh

@@ -6,6 +6,8 @@ set -Eeuo pipefail
 : ${DHCP:='N'}
 : ${MAC:='82:cf:d0:5e:57:66'}
 
+: ${CONTROL_PORTS:=''}
+
 : ${VM_NET_TAP:='qemu'}
 : ${VM_NET_DEV:='eth0'}
 : ${VM_NET_MAC:="$MAC"}
@@ -146,11 +148,17 @@ configureNAT () {
 
   ip link set dev "${VM_NET_TAP}" master dockerbridge
 
+  CONTROL_PORT_ARGS=''
+  for PORT in $CONTROL_PORTS ; do
+    CONTROL_PORT_ARGS="$CONTROL_PORT_ARGS ! --dport $PORT"
+  done
+
   # Add internet connection to the VM
   IP=$(ip address show dev "${VM_NET_DEV}" | grep inet | awk '/inet / { print $2 }' | cut -f1 -d/)
 
   iptables -t nat -A POSTROUTING -o "${VM_NET_DEV}" -j MASQUERADE
-  iptables -t nat -A PREROUTING -i "${VM_NET_DEV}" -d "${IP}" -p tcp  -j DNAT --to $VM_NET_IP
+  # shellcheck disable=SC2086
+  iptables -t nat -A PREROUTING -i "${VM_NET_DEV}" -d "${IP}" -p tcp $CONTROL_PORT_ARGS -j DNAT --to $VM_NET_IP
   iptables -t nat -A PREROUTING -i "${VM_NET_DEV}" -d "${IP}" -p udp  -j DNAT --to $VM_NET_IP
 
   if (( KERNEL > 4 )); then