prevent using ./configure.sh directly which could brick

users' host machines.

Author: tesuji

README.md

@@ -79,6 +79,15 @@ mkdir qemu/build && cd qemu/build && ../configure --target-list=x86_64-softmmu -
 cd scripts/create-image/ && ./create-image.sh && cd ../..
 ~~~
 
+Or if you prefer using docker to build your image:
+~~~
+cd scripts/create-image/
+docker build -t img .
+docker run -v $(pwd):/mnt --privileged --rm img
+~~~
+
+Notice that `privileged` is necessary because we want to use `/dev/loop*` inside docker.
+
 ### Step 4: Install uv
 ~~~
 pip install uv

scripts/create-image/Dockerfile

@@ -32,5 +32,5 @@ RUN ./debootstrap.sh
 
 # will copy the img file to /mnt. Need --privilege flag for docker run.
 COPY --chmod=0755 configure.sh /src/
-CMD ["bash", "-x", "./configure.sh"]
+CMD ["bash", "-c", "set -ex; source ./configure.sh"]
 

scripts/create-image/configure.sh

@@ -2,6 +2,20 @@
 # Copyright 2025 syzkaller project authors. All rights reserved.
 # Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
 
+usage() {
+    echo "Please use the ./create-image.sh instead." >&2
+    exit 1
+}
+
+# Prevent execution if not sourced
+(return 0 2>/dev/null) || {
+    usage
+}
+
+if [ -z "$DIR" ] || [ "$(realpath "$DIR")" = / ]; then
+    usage
+fi
+
 # Set some defaults and enable promtless ssh to the machine for root.
 sudo sed -i '/^root/ { s/:x:/::/ }' $DIR/etc/passwd
 echo 'T0:23:respawn:/sbin/getty -L ttyS0 115200 vt100' | sudo tee -a $DIR/etc/inittab