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https://github.com/davidar/bootsh
Bootstrappable, self-hosting POSIX shell
https://github.com/davidar/bootsh
Last synced: 24 days ago
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Bootstrappable, self-hosting POSIX shell
- Host: GitHub
- URL: https://github.com/davidar/bootsh
- Owner: davidar
- License: mit
- Created: 2024-04-25T10:33:50.000Z (10 months ago)
- Default Branch: master
- Last Pushed: 2024-05-22T11:24:11.000Z (9 months ago)
- Last Synced: 2024-05-23T03:22:43.374Z (9 months ago)
- Language: C
- Homepage:
- Size: 18.7 MB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# *boot*sh
A comprehensive POSIX userspace, including a C compiler, in a single tiny (<1MB) executable.
- **Bootstrappable:** *boot*sh contains a variety of builtin commands (including `grep`, `diff`, `sed`, `xzcat`, `sha1sum`, `ninja` and many more) providing a solid POSIX base to [bootstrap a full GNU/Linux distribution from source](https://github.com/sabotage-linux/sabotage).
- **Self-hosting:** *boot*sh can compile itself from source, thanks to its builtin `cc` command which implements a full C99 compiler.
- **Tiny:** *boot*sh can be compiled into a single ~700KB binary executable in under 10 seconds. With [UPX](https://upx.github.io/) it can be reduced to half that size.
## Build
Just run `./configure && ninja`. The configure script will prompt you for any missing build dependencies. If you don't have `ninja`, you can run `make` to bootstrap with the builtin copy of [samurai](https://github.com/michaelforney/samurai).
## Usage
A [Docker image](https://hub.docker.com/r/davidar/bootsh/tags) is provided to demonstrate how *boot*sh can be used in a self-contained environment.
```sh
docker run --rm -it davidar/bootsh
```
This image contains four files:
- `/bin/sh`: the *boot*sh executable
- `/bin/init`: a small shell script for constructing the root filesystem and bootstrapping musl libc from source
- `/bin/configure-musl.sh`: sets up an alternative ninja-based build system for musl
- `/bin/awk`: a [C script](scripts/wak.c) (note the `#!/bin/cc -run` interpreter line) which is JIT compiled as needed
Upon running the Docker image, it will bootstrap itself by constructing a minimal root filesystem on top of this.
Alternatively, you can build a minimal Linux distribution by running
```sh
scripts/build-docker.sh --kernel
```
This will produce a compressed kernel in `build/bzImage` and a compressed root filesystem in `build/initramfs.cpio.xz` (whose contents are the same as the Docker image).
Together they occupy less than 2MB. To boot the kernel in QEMU, run
```sh
scripts/run-qemu.sh
```
## POSIX Compliance
*boot*sh implements all of the [mandatory POSIX commands](https://en.wikipedia.org/wiki/List_of_POSIX_commands)
(and a number of optional commands) except for the following:
- system administration: `at`, `batch`, `crontab`, `df`, `logger`, `lp`, `man`, `newgrp`, `ps`
- text/locale processing: `csplit`, `gencat`, `iconv`, `locale`, `localedef`, `pr`, `split`
- interactive tools: `ed`, `mailx`, `mesg`, `unexpand`, `write`
- terminal control: `stty`, `tabs`, `tput`
- miscellaneous: `bc`, `join`, `m4`, `pathchk`, `pax`, `tsort`
## Credits
*boot*sh is based on several MIT/BSD licensed projects:
- The [Debian Almquist shell](http://gondor.apana.org.au/~herbert/dash/)
- Command line utilities from [toybox](http://landley.net/toybox/)
- The MIT-relicensed parts of the [Tiny C Compiler](https://bellard.org/tcc/)
- Version 8.0 of [compiler-rt](https://compiler-rt.llvm.org/) (before it was relicensed from MIT to Apache 2.0)
- `ar` from the [Cosmopolitan](https://github.com/jart/cosmopolitan) project
- [wak](https://github.com/raygard/wak), the one-file implementation of `awk`
- [samurai](https://github.com/michaelforney/samurai), a reimplementation of [Ninja](https://github.com/ninja-build/ninja)
- [musl libc](https://musl.libc.org/)