The curious case of binfmt for x86 emulation for ARM Docker
2 days ago
- #ARM-emulation
- #binfmt_misc
- #Docker
- Two methods for setting up x86 emulation on ARM showed identical system configurations but behaved differently in Docker.
- The Docker method using `tonistiigi/binfmt` worked, while the `systemd-binfmt` approach failed despite identical `/proc/sys/fs/binfmt_misc` configurations.
- The key difference was the `F` (fix binary) flag, which ensures the emulator binary stays in memory, crucial for Docker's namespaces.
- The `systemd-binfmt` setup used dynamically linked QEMU binaries, which failed in Docker due to missing dependencies in namespaces.
- A solution was found by manually copying static QEMU binaries from the Docker image and updating the `systemd-binfmt` configuration.
- Lessons include the importance of understanding kernel features like `binfmt_misc` and the limitations of dynamically linked binaries in containers.
- Debugging highlighted the challenges of relying on LLMs for technical troubleshooting due to their tendency to hallucinate incorrect information.