1 files changed, 272 insertions, 0 deletions
diff --git a/bin/debvm-run b/bin/debvm-run
new file mode 100755
index 0000000..c2a3f21
--- /dev/null
+++ b/bin/debvm-run
@@ -0,0 +1,272 @@
+#!/bin/sh
+# Copyright 2022 Helmut Grohne <helmut@subdivi.de>
+# SPDX-License-Identifier: MIT
+
+: <<'POD2MAN'
+=head1 NAME
+
+debvm-run - Run a VM image created by debvm-create
+
+=head1 SYNOPSIS
+
+B<debvm-run> [B<-g>] [B<-i> F<image>] [B<-s> I<sshport>] [B<--> I<qemu options>]
+
+=head1 DESCRIPTION
+
+B<debvm-run> is essentially a thin wrapper around B<qemu> for running a virtual machine image created by B<debvm-create> or something compatible.
+The virtual machine image is expected to be a raw ext4 image with file system label B<debvm>.
+The architecture of the machine is detected from the contained F</bin/true>.
+It must contain a symbolic link pointing to a kernel image at F</vmlinuz> or F</vmlinux> depending on the architecture and a symbolic link pointing to an initrd image at F</initrd.img>.
+Both are extracted and passed to B<qemu>.
+A net interface configured for user mode is added automatically.
+
+=head1 OPTIONS
+
+=over 8
+
+=item B<-g>, B<--graphical>
+
+By default, the option B<-nographic> is passed to B<qemu> and one interacts with the serial console of the machine.
+This configuration is skipped in the presence of this option.
+
+=item B<-i> F<image>, B<--image>=F<image>
+
+This option specifies the location of the virtual machine image file.
+By default F<rootfs.ext4> in the working directory is used.
+
+=item B<-s> I<sshport>, B<--sshport>=I<sshport>
+
+If given, B<qemu> is configured to pass connections to I<127.0.0.1:sshport> to port 22 of the virtual machine.
+You can connect to your virtual machine without updating your known hosts like this:
+
+    ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -p $sshport root@127.0.0.1
+
+=item B<--> I<qemu options>
+
+All options beyond a double dash are passed to B<qemu>.
+This can be used to configure additional hardware components.
+One possible use of this method is passing B<-snapshot> to avoid modifying the virtual machine image.
+
+=back
+
+=head1 EXAMPLES
+
+Run a virtual machine stored in the image F<rootfs.ext4> (the default) with
+local port 8022 routed to port 22 of the virtual machine. The B<-snapshot>
+argument is passed to QEMU and prevents any permanent changes to
+F<rootfs.ext4>, resulting in an ephemeral run.
+
+    debvm-run -s 8022 -i rootfs.ext4 -- -snapshot
+
+=head1 LIMITATIONS
+
+Due to the way kernel and bootloader are being extracted before running B<qemu>, one cannot upgrade a kernel and then just reboot.
+Attempting to do so, will still use the old kernel.
+Instead, B<qemu> must be terminated and B<debvm-run> should be launched again to pick up the new kernel.
+In order to avoid accidental reboots, one may pass B<-no-reboot> to B<qemu>.
+
+=head1 SEE ALSO
+
+    debvm-create(1) qemu(1)
+
+=cut
+POD2MAN
+
+set -u
+
+IMAGE=rootfs.ext4
+SSHPORT=
+GRAPHICAL=
+
+nth_arg() {
+	shift "$1"
+	printf "%s" "$1"
+}
+
+die() {
+	echo "$*" 1>&2
+	exit 1
+}
+usage() {
+	die "usage: $0 [-g] [-i image] [-s sshport] [-- qemu options]"
+}
+usage_error() {
+	echo "error: $*" 1>&2
+	usage
+}
+
+opt_graphical() {
+	GRAPHICAL=1
+}
+opt_image() {
+	IMAGE=$1
+}
+opt_sshport() {
+	SSHPORT=$1
+}
+
+while getopts :gi:s:-: OPTCHAR; do
+	case "$OPTCHAR" in
+		g)	opt_graphical		;;
+		i)	opt_image "$OPTARG"	;;
+		s)	opt_sshport "$OPTARG"	;;
+		-)
+			case "$OPTARG" in
+				help)
+					usage
+				;;
+				graphical|image|sshport)
+					test "$OPTIND" -gt "$#" && usage_error "missing argument for --$OPTARG"
+					"opt_$OPTARG" "$(nth_arg "$OPTIND" "$@")"
+					OPTIND=$((OPTIND+1))
+				;;
+				image=*|sshport=*)
+					"opt_${OPTARG%%=*}" "${OPTARG#*=}"
+				;;
+				*)
+					usage_error "unrecognized option --$OPTARG"
+				;;
+			esac
+		;;
+		:)
+			usage_error "missing argument for -$OPTARG"
+		;;
+		'?')
+			usage_erro "unrecognized option -$OPTARG"
+		;;
+		*)
+			die "internal error while parsing command options, please report a bug"
+		;;
+	esac
+done
+shift "$((OPTIND - 1))"
+
+test -f "$IMAGE" || die "image '$IMAGE' not found"
+test -s "$IMAGE" || die "image '$IMAGE' is empty"
+
+if ! printf '\123\357' | cmp --bytes=2 "$IMAGE" - 1080; then
+	die "image '$IMAGE' is not in ext4 format"
+fi
+
+if ! printf 'debvm\000' | cmp --bytes=6 "$IMAGE" - 1144; then
+	die "image '$IMAGE' was not created by debvm-create (wrong disk label)"
+fi
+
+cleanup() {
+	set +x
+	test -n "$KERNELTMP" && rm -f "$KERNELTMP"
+	test -n "$INITRDTMP" && rm -f "$INITRDTMP"
+}
+
+trap cleanup EXIT INT TERM QUIT
+
+KERNELTMP=$(mktemp)
+INITRDTMP=$(mktemp)
+
+ARCHITECTURE=$(dpkg --print-architecture)
+VMARCH=$ARCHITECTURE
+if command -v elf-arch >/dev/null 2>&1; then
+	/sbin/debugfs "$IMAGE" -R "cat /bin/true" > "$KERNELTMP"
+	VMARCH=$(elf-arch "$KERNELTMP")
+fi
+case "$VMARCH" in
+	mips*|ppc64el)
+		KERNELLINK=vmlinux
+	;;
+	*)
+		KERNELLINK=vmlinuz
+	;;
+esac
+
+KERNELNAME=$(/sbin/debugfs "$IMAGE" -R "stat $KERNELLINK" | sed 's/Fast link dest: "\(.*\)"/\1/;t;d')
+INITRDNAME=$(/sbin/debugfs "$IMAGE" -R "stat initrd.img" | sed 's/Fast link dest: "\(.*\)"/\1/;t;d')
+
+test -n "$KERNELNAME" || die "failed to discover kernel image"
+test -n "$INITRDNAME" || die "failed to discover initrd image"
+
+KERNEL_CMDLINE="root=LABEL=debvm rw"
+NETDEV="user,id=net0"
+
+set -- \
+	-no-user-config \
+	-name "debvm-run $IMAGE" \
+	-m 1G \
+	-kernel "$KERNELTMP" \
+	-initrd "$INITRDTMP" \
+	-object rng-random,filename=/dev/urandom,id=rng0 -device virtio-rng-pci,rng=rng0 \
+	-drive "media=disk,format=raw,discard=unmap,file=$IMAGE,if=virtio,cache=unsafe" \
+	-device "virtio-net-pci,netdev=net0" \
+	"$@"
+
+MAX_SMP=
+if test "$ARCHITECTURE" = "$VMARCH"; then
+	QEMU=kvm
+	# While kvm will fall back gracefully, the following options can only
+	# be passed when kvm really is available.
+	if test -w /dev/kvm; then
+		set -- -enable-kvm -cpu host "$@"
+	fi
+	case "$VMARCH" in
+		arm64)
+			set -- -machine type=virt,gic-version=host "$@"
+		;;
+	esac
+else
+	QEMU="qemu-system-$VMARCH"
+	case "$VMARCH" in
+		arm64)
+			QEMU=qemu-system-aarch64
+			set -- -machine virt -cpu max "$@"
+		;;
+		arm|armel|armhf)
+			QEMU=qemu-system-arm
+			set -- -machine virt -cpu max "$@"
+		;;
+		ppc64el)
+			QEMU=qemu-system-ppc64
+		;;
+		mips64el)
+			MAX_SMP=1
+			set -- -cpu 5KEc "$@"
+		;;
+		mipsel)
+			MAX_SMP=1
+		;;
+		riscv64)
+			set -- -machine virt "$@"
+		;;
+	esac
+fi
+if test -z "$MAX_SMP" || test "$MAX_SMP" -gt 1; then
+	NPROC=$(nproc)
+	test -n "$MAX_SMP" && test "$NPROC" -gt "$MAX_SMP" && NPROC=$MAX_SMP
+	set -- -smp "$NPROC" "$@"
+fi
+
+if test -z "$GRAPHICAL"; then
+	set -- -nographic "$@"
+	case "$VMARCH" in
+		amd64|i386)
+			KERNEL_CMDLINE="$KERNEL_CMDLINE console=ttyS0"
+		;;
+	esac
+fi
+
+if test -n "$SSHPORT"; then
+	NETDEV="$NETDEV,hostfwd=tcp:127.0.0.1:$SSHPORT-:22"
+fi
+DNSSEARCH=$(dnsdomainname)
+if test -n "$DNSSEARCH"; then
+	NETDEV="$NETDEV,domainname=$DNSSEARCH"
+fi
+set -- \
+	-append "$KERNEL_CMDLINE" \
+	-netdev "$NETDEV" \
+	"$@"
+
+set -ex
+
+/sbin/debugfs "$IMAGE" -R "cat $KERNELNAME" > "$KERNELTMP"
+/sbin/debugfs "$IMAGE" -R "cat $INITRDNAME" > "$INITRDTMP"
+
+"$QEMU" "$@"