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make aroot builds a SchFS root from Alpine's minirootfs, the packages ports/alpine/world lists, and SchOS itself as the signed apk package schos-base, in its own repository inside the root. apk add installs from Alpine; apk upgrade updates both. Booted: zsh is Alpine's, apk update sees 28669 packages, apk add htop works, and so does xorg-server. world.lock pins every package with its sha256; a build fetches only what dist/alpine/ lacks and never looks for newer versions. make alpine-lock is the one step that does. Alpine's zsh, busybox commands and hwdata replace SchOS's copies; SchOS keeps its own tools, toybox's other commands, and static mksh, which schinit's recovery shell now tries first. Also: the dependency-file include matched Alpine's usr/lib/sysctl.d, a directory, and stopped every make. See docs/plan/alpine.md. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
73 lines
3.3 KiB
Markdown
73 lines
3.3 KiB
Markdown
# apk: Alpine's packages on SchOS
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Alpine is musl with a different init, and SchOS is musl with a different
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kernel. Alpine's binaries run on SchOS unmodified: its dynamic linker, its
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busybox, and apk itself, fetching over TLS through SchOS's network stack.
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So instead of porting programs one at a time, SchOS can install them.
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## The model
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The root filesystem is an apk-managed root:
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| Part | Where it comes from |
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| musl, busybox, apk-tools, alpine-keys, CA certificates | Alpine's minirootfs (`ports/alpine`) |
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| what `ports/alpine/world` lists (zsh, terminfo, ...) | Alpine's packages, pinned in `world.lock` |
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| schinit, its jobs, SchOS's tools, toybox, mksh, configuration | **schos-base**, an apk package the build makes from `sysroot/` |
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`apk add` installs anything from Alpine's main and community repositories.
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`apk upgrade` updates Alpine's packages, and schos-base from the SchOS
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repository at `/var/lib/schos/repo`.
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PID 1 is still schinit. Alpine's OpenRC is not installed, and packages that
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ship OpenRC services install them where nothing reads them.
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## Who owns what
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Where Alpine and SchOS both have a program, Alpine's wins, and SchOS keeps
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only what is its own (see `tools/posix/mkaroot.sh`):
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- `/bin/sh`, `cat`, `sed`, `find` and the rest are busybox. Alpine's package
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scripts are written against busybox.
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- zsh is Alpine's. SchOS keeps its `zshrc` and `zshenv` (`replaces=zsh`).
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- `/etc/os-release` and `/etc/motd` are SchOS's (`replaces=`).
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- `passwd`, `group` and `profile` are Alpine's. schos-base's post-install
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sets root's shell to zsh, and SchOS's profile is `/etc/profile.d/schos.sh`.
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- mksh is `/bin/mksh`. schinit's recovery shell looks for it first because it
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is static: a broken musl cannot take recovery down with it.
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## Building
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make aroot build/aroot.img: the root, as a SchFS volume
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make qemu-aroot boot it
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make alpine-lock re-resolve world against Alpine (needs the network)
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Only `alpine-lock` asks Alpine what is current. A normal build installs
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exactly what `world.lock` names: files in `dist/alpine/`, fetched once and
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checked against the lock's sha256, and against Alpine's signatures by apk.
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schos-base and its repository index are signed with a key made on the first
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build (`build/apk-keys/`, never committed). The root trusts it beside
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Alpine's keys.
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## Kernel work this needed
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All of it found by running apk:
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- **TCP receive window:** it reopened before the reader drained, so lwIP
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refused data and the sender waited on retransmission timers (5 KB/s). It
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now reopens on read, with a 32-segment window.
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- **mmap address reuse:** freed ranges were never reused, so musl's malloc
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used up the 256 mapping records with 780 MB of RAM free.
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- **unlinkat / renameat:** bare `-1`, read as EPERM, where apk expects ENOENT;
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renameat could not replace its target, and wrote v1 dirents into SchFS.
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- **`#!` scripts in execve**, and ENOEXEC: apk runs triggers directly.
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- **chroot**, and mounting devtmpfs and proc more than once.
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## Next
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- The live ISO and USB stick are still the ramdisk root. They need the apk
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root on the stick itself, or an installer that writes it to a disk.
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- Xorg from apk (`xorg-server xf86-video-fbdev xf86-input-evdev`) instead of
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the hand port in [xorg.md](xorg.md). The packages install; running them is
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the next test.
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