# Foundry OS: decisions and plan

## Tyler's answers to the proposal (2026-10-31)

| # | Question | Decision |
|---|---|---|
| 1 | Name, place, history | The OS is **Foundry OS**, in `/workspace/foundry` (local git only: no remote, no push). The kernel's `user/` and `disk/` histories were kept with `git subtree split`, done in a scratch clone at a55b41d (`/workspace/foundry-scratch/rk`), never in `/workspace/rust-kernel`. |
| 2 | What stays in the kernel | The ABI test programs stay as kernel fixtures: `hello evil spin demo child overflow forktest cowtest mmaptest sigtest threads echoserver ptytest nbtest fputest pathtest libctest coretest unixtest rawabi` and the musl ones `vdsotest piehello piethreads dynhello remaptest`. The shell, the tools and the net/sys programs moved here. |
| 3 | Which shell | The Rust shell stays the interactive login shell, renamed **rbsh**, keeping its DOS commands (`run`/`start`, `dir`/`type`/`cls`...) and drive letters. **dash** (later busybox `ash`) becomes `/bin/sh` for POSIX scripts once the root is ext2. Under contract v1 rbsh is still installed as `/bin/sh`, because that is the path the kernel runs. |
| 4 | Root file system | Later: an **ext2 root**, so `A:` = `/` is the OS disk. The FAT32 disk stays as a **data disk** (`B:`). Plus an **exFAT data partition** for sharing files with Windows/macOS. M1 keeps contract v1 (today's layout). |
| 5 | Name clashes | The Rust tools stay the default. busybox/sbase applets go under **`/usr/lib/busybox`**, off the default `PATH` (call them by full path, or add the directory to `PATH` yourself). |
| 6 | Tarballs | **Not in git.** A git-ignored download cache (`cache/`), each file pinned by SHA256 (`toolchain/musl/musl.sha256` + `fetch.sh`; `ports/<name>/<name>.sha256`). |
| 7 | Which kernel | A **pinned commit**: `KERNEL_REV=a55b41d` (Rustbelt 0.19.0) in `config.mk`, bumped deliberately. |
| 8 | Box packages | Small build packages are OK (`make`, `bzip2`, `musl-tools`, `autoconf`). |

## Disk layout later (contract v2, not built yet)

```
foundry.img (GPT)
├── 1  ext2   "Linux root (x86-64)" type   → mounted at /       (A:)  the OS: /bin /sbin /etc /usr ...
└── 2  exFAT  "Microsoft basic data" type  → /mnt/diskN          data shared with other computers
data.img (separate disk, today's FAT32)    → /mnt/disk0          (B:)  a plain data disk
```

Inside the ext2 root:

```
/bin       rbsh, the Rust tools (ls cat grep ...), dash as /bin/sh
/sbin      init (Rust, M3)
/etc       passwd group hosts resolv.conf motd profile rc   (rootfs/etc/)
/usr/lib/busybox   busybox + applet symlinks, off the default PATH (M5)
```

## Milestones

| | Goal | Status |
|---|---|---|
| **M1** | Foundry OS builds the same image; the kernel's self-test passes on it | **done**: `make test` passes; `make compare` shows the same 44 programs and identical non-program files |
| M1b | `rbrt` becomes a real library crate; rbsh's parser tests run on the host | next |
| M2 | musl hello + probes in `/bin`, built with plain `musl-gcc -static-pie` | the toolchain pieces exist (`make musl`, `c/hello-musl.c`) |
| M3 | dash as `/bin/sh`, ext2 root (contract v2), Rust `/sbin/init` | needs kernel K5 |
| M4 | sbase tools | needs testing per tool (docs/syscall-gaps.md) |
| M5 | busybox in `/usr/lib/busybox` | `bzip2` for the tarball |