# youki: A container runtime in Rust
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youki is an implementation of [runtime-spec](https://github.com/opencontainers/runtime-spec) in Rust, referring to [runc](https://github.com/opencontainers/runc).
# About the name
youki is pronounced as /joʊki/ or yoh-key.
youki is named after a Japanese word 'youki', which means 'a container'. In Japanese language, youki also means 'cheerful', 'merry', or 'hilarious'.
# Motivation
Here is why I am rewriting a new container runtime in Rust.
- Rust is one of the best languages to implement oci-runtime. Many container tools are written in Go. It's all very nice products. However, the container runtime requires the use of system calls, which requires a bit of special handling when implemented in Go. This is too tricky(e.g. _namespaces(7)_, _fork(2)_); with Rust, it's not that tricky and you can use system calls. Also, unlike C, Rust provides the benefit of memory management. Rust is not yet a major player in the container field, and Rust has the potential to contribute more to this field. I hope to be one of the examples of how Rust can be used in this field.
- youki has the potential to be faster and use less memory than runc. This means that it can work in environments with tight memory usage. I don't have any benchmarks, etc., as it is not yet fully operational, but I expect that it will probably perform better when implemented in Rust. In fact, [crun](https://github.com/containers/crun#performance), a container runtime implemented in C, is quite high performance. For example, it may be possible to experiment with asynchronous processing using async/await in some parts.
- The development of [railcar](https://github.com/oracle/railcar) has been suspended. This project was very nice but is no longer being developed. This project is inspired by it.
- I have fun implementing this. In fact, this may be the most important.
# Related project
- [containers/oci-spec-rs](https://github.com/containers/oci-spec-rs) - OCI Runtime and Image Spec in Rust
# Status of youki
youki is not at the practical stage yet. However, it is getting closer to practical use, running with docker and passing all the default tests provided by [opencontainers/runtime-tools](https://github.com/opencontainers/runtime-tools).
| Feature | Description | State |
| :------------: | :---------------------------------------------: | :-------------------------------------------------------------------------------------------------: |
| Docker | Running via Docker | ✅ |
| Podman | Running via Podman | It works, but cgroups isn't supported. WIP on [#24](https://github.com/containers/youki/issues/24) |
| pivot_root | Change the root directory | ✅ |
| Mounts | Mount files and directories to container | ✅ |
| Namespaces | Isolation of various resources | ✅ |
| Capabilities | Limiting root privileges | ✅ |
| Cgroups v1 | Resource limitations, etc | ✅ |
| Cgroups v2 | Improved version of v1 | Support is complete except for devices. WIP on [#78](https://github.com/containers/youki/issues/78) |
| Seccomp | Filtering system calls | WIP on [#25](https://github.com/containers/youki/issues/25) |
| Hooks | Add custom processing during container creation | ✅ |
| Rootless | Running a container without root privileges | It works, but cgroups isn't supported. WIP on [#77](https://github.com/containers/youki/issues/77) |
| OCI Compliance | Compliance with OCI Runtime Spec | 45 out of 55 test cases passing |
# Design and implementation of youki
More details are in the works [#14](https://github.com/containers/youki/issues/14)
# Getting Started
Local build is only supported on linux.
For other platforms, please use [Vagrantfile](#setting-up-vagrant) that we prepared.
## Requires
- Rust(See [here](https://www.rust-lang.org/tools/install))
- Docker(See [here](https://docs.docker.com/engine/install))
## Dependencies
### Debian, Ubuntu and related distributions
```sh
$ sudo apt-get install \
pkg-config \
libsystemd-dev \
libdbus-glib-1-dev \
build-essential \
libelf-dev
```
### Fedora, Centos, RHEL and related distributions
```sh
$ sudo dnf install \
pkg-config \
systemd-devel \
dbus-devel \
elfutils-libelf-devel \
```
## Build
```sh
$ git clone git@github.com:containers/youki.git
$ cd youki
$ ./build.sh
$ ./youki -h # you can get information about youki command
```
## Tutorial
Let's try to run a container that executes `sleep 30` with youki. This tutorial may need root permission.
```sh
$ git clone git@github.com:containers/youki.git
$ cd youki
$ ./build.sh
$ mkdir -p tutorial/rootfs
$ cd tutorial
# use docker to export busybox into the rootfs directory
$ docker export $(docker create busybox) | tar -C rootfs -xvf -
```
Then, we need to prepare a configuration file. This file contains metadata and specs for a container, such as the process to run, environment variables to inject, sandboxing features to use, etc.
```sh
$ ../youki spec # will generate a spec file named config.json
```
We can edit the `config.json` to add customized behaviors for container. Here, we modify the `process` field to run `sleep 30`.
```json
"process": {
...
"args": [
"sleep", "30"
],
...
}
```
Then we can explore the lifecycle of a container:
```sh
$ sudo ./youki create -b tutorial tutorial_container # create a container with name `tutorial_container`
$ sudo ./youki state tutorial_container # you can see the state the container is `created`
$ sudo ./youki start tutorial_container # start the container
$ sudo ./youki list # will show the list of containers, the container is `running`
$ sudo ./youki delete tutorial_container # delete the container
```
Change the command to be executed in `config.json` and try something other than `sleep 30`.
## Usage
Starting the docker daemon.
```
$ dockerd --experimental --add-runtime="youki=$(pwd)/target/x86_64-unknown-linux-gnu/debug/youki"
```
In case you get an error like :
```
failed to start daemon: pid file found, ensure docker is not running or delete /var/run/docker.pid
```
That means your normal Docker daemon is running, and it needs to be stopped. For that, open a new shell in same directory and run :
```
$ systemctl stop docker # might need root permission
```
Now in the same shell run the first command, which should start the docker daemon.
You can use youki in a different terminal to start the container.
```
$ docker run -it --rm --runtime youki busybox
```
Afterwards, you can close the docker daemon process in other the other terminal. To restart normal docker daemon (if you had stopped it before), run :
```
$ systemctl start docker # might need root permission
```
### Integration test
Go and node-tap are required to run integration test. See the [opencontainers/runtime-tools](https://github.com/opencontainers/runtime-tools) README for details.
```
$ git submodule update --init --recursive
$ ./integration_test.sh
# run specific test_cases with pattern
$ ./integration_test.sh linux_*
```
### Setting up Vagrant
You can try youki on platforms other than linux by using the Vagrantfile we have prepared.
```
$ git clone git@github.com:containers/youki.git
$ cd youki
$ vagrant up
$ vagrant ssh
# in virtual machine
$ cd youki
$ ./build.sh
```
# Community
We also have an active [Discord](https://discord.gg/h7R3HgWUct) if you'd like to come and chat with us.
# Contribution
This project welcomes your PR and issues.
For example, refactoring, adding features, correcting English, etc.
If you need any help, you can contact me on [Twitter](https://twitter.com/utam0k).
Thanks to all the people who already contributed!
