qemu-image-builder

#!/usr/bin/make -f
PREFIX := $(shell pwd)
DISTRIBUTION := unstable
APT_MIRROR := "http://localhost:9999/debian"
WORKDIR := /home/abhijit/tmp/qemu-image-builder-work
BOOTSTRAP_DIR := $(WORKDIR)/debootstrap
DEBOOTSTRAP := /usr/sbin/debootstrap
DEBOOTSTRAP_OPTS := --no-check-certificate --no-check-gpg --include=linux-image-amd64,openssh-server,qemu-guest-agent
DEST := $(WORKDIR)/build

build: squashfs
	@cp -v -f \
		$(BOOTSTRAP_DIR)/boot/vmlinuz-4.6.0-1-amd64 \
		$(BOOTSTRAP_DIR)/boot/initrd.img-4.6.0-1-amd64 \
			$(DEST)
	@chmod +x $(DEST)/run

squashfs: bootstrap overlay-boot launcher auth
	@mksquashfs $(BOOTSTRAP_DIR) $(DEST)/debootstrap.squashfs -no-progress -noappend

makedirs:
	@mkdir -p $(DEST)
	@mkdir -p $(WORKDIR)
	@mkdir -p $(BOOTSTRAP_DIR)

auth:
	@$(shell echo "root:root"|chpasswd -R $(BOOTSTRAP_DIR))

clean:
	@rm -rf $(BOOTSTRAP_DIR)
	@mkdir -p $(BOOTSTRAP_DIR)
	@rm -f $(WORKDIR)/deboostrap.squashfs

overlay-boot: overlay overlay-hook
	@chmod +x $(BOOTSTRAP_DIR)/usr/share/initramfs-tools/hooks/overlay-hook
	@rm -f $(BOOTSTRAP_DIR)/boot/initrd.img-4.6.0-1-amd64
	@chroot $(BOOTSTRAP_DIR) update-initramfs -k 4.6.0-1-amd64 -c

bootstrap: makedirs
	@$(DEBOOTSTRAP) $(DEBOOTSTRAP_OPTS) $(DISTRIBUTION) $(BOOTSTRAP_DIR) $(APT_MIRROR)

overlay-hook:
	@cat <<- EOF > $(BOOTSTRAP_DIR)/usr/share/initramfs-tools/hooks/overlay-hook
	#!/bin/sh -e
	. /usr/share/initramfs-tools/hook-functions
	case "$$1" in
	    prereqs)
				echo ""
				exit 0
	    ;;
	esac
	manual_add_modules squashfs
	manual_add_modules overlay
	EOF

overlay:
	@cat <<- EOF > $(BOOTSTRAP_DIR)/usr/share/initramfs-tools/scripts/overlay
	mountroot() {
	    modprobe squashfs
	    modprobe overlay
	    mount -t squashfs /dev/vda /root
			mkdir -p /overlay
	    mount -t tmpfs -osize=512m none /overlay
	    mkdir -p /overlay/workdir /overlay/upperdir
	    mount -t overlay -olowerdir=/root,upperdir=/overlay/upperdir,workdir=/overlay/workdir live-root /root
	}
	EOF

launcher:
	@cat <<- EOF > $(DEST)/run
	#!/bin/sh
	set -eu
	basedir=\$$(dirname \$$(readlink -f \$$0))
	qemu-system-x86_64 -cpu host -enable-kvm -m 1024 -vga virtio -kernel \\
		\$$basedir/vmlinuz-4.6.0-1-amd64 -initrd \\
		\$$basedir/initrd.img-4.6.0-1-amd64 -append \\
		'rootfstype=squashfs boot=overlay root=/dev/vda quiet' -drive \\
		if=virtio,format=raw,file=\$$basedir/debootstrap.squashfs
	EOF

.ONESHELL: overlay overlay-hook launcher