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# RustyHermit: libhermit-rs
[](https://hermitcore.github.io/libhermit-rs/hermit/)
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[](https://matrix.osbyexample.com:3008)
_libhermit-rs_ is the kernel of the [RustyHermit](https://github.com/hermitcore/rusty-hermit) unikernel project.
## Building the kernel
Usually the kernel will be linked as static library to your applications.
- **Rust applications:** Instructions can be found in the [rusty-hermit](https://github.com/hermitcore/rusty-hermit) repository.
- **For C/C++ applications:** Instructions can be found in the [hermit-playground](https://github.com/hermitcore/hermit-playground) repository.
### Standalone static library build
If this does not fit your needs and you want to build the kernel as static library to link afterwards, you need the following:
The Rust **nightly** toolchain ([official webpage](https://www.rust-lang.org/)), the source code of the Rust runtime, and llvm-tools:
```sh
rustup toolchain install nightly
rustup component add rust-src llvm-tools-preview
```
You can then build `libhermit-rs` with the following command
```sh
cargo build -Z build-std=core,alloc,panic_abort --target x86_64-unknown-none-hermitkernel
```
The resulting library then can be found in `target/x86_64-unknown-none-hermitkernel/debug/libhermit.a`
### Control the kernel messages verbosity
_libhermit-rs_ uses the lightweight logging crate [log](https://github.com/rust-lang/log) to print kernel messages.
The environment variable `HERMIT_LOG_LEVEL_FILTER` controls the verbosity.
You can change it by setting it at compile time to a string matching the name of a [LevelFilter](https://docs.rs/log/0.4.8/log/enum.LevelFilter.html).
If the variable is not set, or the name doesn't match, then `LevelFilter::Info` is used by default.
```sh
$ HERMIT_LOG_LEVEL_FILTER=Debug cargo build -Z build-std=core,alloc,panic_abort --target x86_64-unknown-none-hermitkernel
```
## Credits
_libhermit-rs_ is derived from following tutorials and software distributions:
1. Philipp Oppermann's [excellent series of blog posts][opp].
2. Erik Kidd's [toyos-rs][kidd], which is an extension of Philipp Opermann's kernel.
3. The Rust-based teaching operating system [eduOS-rs][eduos].
[opp]: http://blog.phil-opp.com/
[kidd]: http://www.randomhacks.net/bare-metal-rust/
[eduos]: http://rwth-os.github.io/eduOS-rs/
HermitCore's Emoji is provided for free by [EmojiOne](https://www.gfxmag.com/crab-emoji-vector-icon/).
## License
Licensed under either of
* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
* MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
at your option.
## Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
libhermit-rs is being developed on [GitHub](https://github.com/hermitcore/libhermit-rs).
Create your own fork, send us a pull request, and chat with us on [Slack](https://matrix.osbyexample.com:3008)