FAQ

Is this a unikernel? Not strictly. It is a kernel and one process with a syscall boundary between them. Everything else a Linux distribution ships is gone. A single-binary version on Hermit is the stretch goal (Why these kernels).

Why not just use a minimal Linux (Alpine, Nerves, Firecracker)? You can, and make run-m0 shows the same image doing exactly that. The point of the project is the memory-safe kernel underneath and the discipline of an image with three static binaries. The Linux path is kept as the control group.

Why not Nerves? Nerves is Linux (Buildroot) plus the BEAM as the main process, with a full userland underneath (busybox, erlinit). It is production-proven and the right answer for most embedded Elixir. This project removes the userland and swaps the kernel.

Can I run Phoenix? Yes, see A Phoenix application. Pure-BEAM dependencies only.

Can I use NIFs? Only if they are linked statically into beam.smp, the way crypto is. Runtime dlopen is not possible.

Does it do DHCP? Yes, by default. On Linux /init has a client; on Asterinas the kernel has one (ip=dhcp, patch 0004). uniapp.ip= sets a static address instead. See the networking chapter.

Can two images talk over Erlang distribution? Not yet: there is no epmd, and distribution is a non-goal of the MVP. -proto_dist with a custom EPMD module would be the way.

How do I get logs out? The console is the only output. Ship logs over the network from the application.

Why does IEx have no colours? TERM=dumb, because there is no terminfo database in the image.

How big is it really? 9.4 MB image plus 5.8 MB kernel. The VM needs 144 MB of RAM on Asterinas (kernel load address), 128 MB on Linux. beam.smp uses about 62 MB RSS idle.

Why is boot 3 to 4 seconds here when the goal says 2? Those numbers are from QEMU TCG on an Apple Silicon host, emulating x86-64 instruction by instruction. With KVM the BEAM’s JIT warm-up is a fraction of that; not yet measured.

Does it run on real hardware? Untested. Asterinas boots on x86-64 machines with virtio or supported NICs; nothing in the image cares.

Why Alpine for the toolchain? musl, and apk --arch x86_64 --root gives a complete x86-64 sysroot with static OpenSSL in one command, which is what makes the native-plus-cross build simple.

Can I build on an x86-64 machine? Yes; the same Dockerfile runs natively there and the “cross” step is a no-op in spirit (it still produces a static build against the sysroot).