Fix missing head command

docs/TODO.md

@@ -165,6 +165,14 @@ export is read-only + single-namespace = inherently small attack surface.
 - **Confine the target** (whichever): unprivileged, drop caps, seccomp +
   SELinux/AppArmor profile, read-only container, minimal mounts; minimal
   immutable serving image, digest-pinned.
+- **Slim the SPDK image (multi-stage build)**: the current single-stage
+  from-source image is ~600 MB (it keeps the whole toolchain — gcc, meson/ninja,
+  kernel headers, the python venv — plus the SPDK/DPDK source and build trees).
+  Convert `serving/spdk/Dockerfile` to a builder stage + a minimal runtime stage
+  that copies only `nvmf_tgt` + its `ldd` shared libs (libnuma, libssl/crypto,
+  libuuid, libaio…) + `rpc.py`/`python3`. Expect ~150–250 MB (debian-slim base
+  or a static SPDK link trims further). Smaller attack surface + faster pulls,
+  and it pairs with the confinement above.
 - **Network-isolate :4420** so only the boot VLAN reaches the target (compose
   with 802.1X/MACsec segmentation in prod).
 - **Replicas** behind distinct discovery entries (availability is the real risk