# youki: A container runtime in Rust

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<p align="center">
  <img src="docs/youki.png" width="230" height="230">
</p>

youki is an implementation of the [OCI runtime-spec](https://github.com/opencontainers/runtime-spec) in Rust, similar to [runc](https://github.com/opencontainers/runc).  
Your ideas are welcome [here](https://github.com/containers/youki/issues/10).

# About the name

youki is pronounced as /joʊki/ or yoh-key.
youki is named after the Japanese word 'youki', which means 'a container'. In Japanese language, youki also means 'cheerful', 'merry', or 'hilarious'.

# Motivation

Here is why we are writing a new container runtime in Rust.

- Rust is one of the best languages to implement the oci-runtime spec. Many very nice container tools are currently written in Go. 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, unlike in C, Rust provides the benefit of memory safety. While Rust is not yet a major player in the container field, it has the potential to contribute a lot: something this project attempts to exemplify.
- youki has the potential to be faster and use less memory than runc, and therefore work in environments with tight memory usage requirements. Here is a simple benchmark of a container from creation to deletion.
  | Runtime | Time (mean ± σ) | Range (min … max) |
  | :-----: | :-----------------: | :-----------------: |
  | youki | 198.4 ms ± 52.1 ms | 97.2 ms … 296.1 ms |
  | runc | 352.3 ms ± 53.3 ms | 248.3 ms … 772.2 ms |
  | crun | 153.5 ms ± 21.6 ms | 80.9 ms … 196.6 ms |
  <details>
  <summary>Details about the benchmark</summary>

  - A command used for the benchmark
    ```console
    $ hyperfine --prepare 'sudo sync; echo 3 | sudo tee /proc/sys/vm/drop_caches' --warmup 10 --min-runs 100 'sudo ./youki create -b tutorial a && sudo ./youki start a && sudo ./youki delete -f a'
    ```
  - Environment
  `console $ ./youki info Version 0.0.1 Kernel-Release 5.11.0-41-generic Kernel-Version #45-Ubuntu SMP Fri Nov 5 11:37:01 UTC 2021 Architecture x86_64 Operating System Ubuntu 21.04 Cores 12 Total Memory 32025 Cgroup setup hybrid Cgroup mounts blkio /sys/fs/cgroup/blkio cpu /sys/fs/cgroup/cpu,cpuacct cpuacct /sys/fs/cgroup/cpu,cpuacct cpuset /sys/fs/cgroup/cpuset devices /sys/fs/cgroup/devices freezer /sys/fs/cgroup/freezer hugetlb /sys/fs/cgroup/hugetlb memory /sys/fs/cgroup/memory net_cls /sys/fs/cgroup/net_cls,net_prio net_prio /sys/fs/cgroup/net_cls,net_prio perf_event /sys/fs/cgroup/perf_event pids /sys/fs/cgroup/pids unified /sys/fs/cgroup/unified CGroup v2 controllers cpu detached cpuset detached hugetlb detached io detached memory detached pids detached device attached Namespaces enabled mount enabled uts enabled ipc enabled user enabled pid enabled network enabled cgroup enabled $ ./youki --version youki version 0.0.1 commit: 0.0.1-0-0be33bf $ runc -v runc version 1.0.0-rc93 commit: 12644e614e25b05da6fd08a38ffa0cfe1903fdec spec: 1.0.2-dev go: go1.13.15 libseccomp: 2.5.1 $ crun --version crun version 0.19.1.45-4cc7 commit: 4cc7fa1124cce75dc26e12186d9cbeabded2b710 spec: 1.0.0 +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +YAJL `
  </details>

- 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).
![youki demo](docs/demo.gif)

|        Feature        |                   Description                   |                                                State                                                |
| :-------------------: | :---------------------------------------------: | :-------------------------------------------------------------------------------------------------: |
|        Docker         |               Running via Docker                |                                                 ✅                                                  |
|        Podman         |               Running via Podman                |                                                 ✅                                                  |
|      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) |
| Systemd cgroup driver |        Setting up a cgroup using systemd        |                                                 ✅                                                  |
|        Seccomp        |             Filtering system calls              |                                                 ✅                                                  |
|         Hooks         | Add custom processing during container creation |                                                 ✅                                                  |
|       Rootless        |   Running a container without root privileges   |                                                 ✅                                                  |
|    OCI Compliance     |        Compliance with OCI Runtime Spec         |                                 ✅ 50 out of 50 test cases passing                                  |
|   CRIU Integration    | Functionality to checkpoint/restore containers  |                           Initial checkpoint support as described in #641                           |

# Design and implementation of youki

The User and Developer Documentation for youki is hosted at [https://containers.github.io/youki/](https://containers.github.io/youki/)

![Architecture](docs/.drawio.svg)

# Getting Started

Local build is only supported on Linux.
For other platforms, please use the [Vagrantfile](#setting-up-vagrant) that we have prepared. You can also spin up a fully preconfigured development environment in the cloud with gitpod.

[![Open in Gitpod](https://gitpod.io/button/open-in-gitpod.svg)](https://gitpod.io/#https://github.com/containers/youki)

## Requires

- Rust(See [here](https://www.rust-lang.org/tools/install)), edition 2021
- Docker(See [here](https://docs.docker.com/engine/install))

## Dependencies

### Debian, Ubuntu and related distributions

```console
$ sudo apt-get install   \
      pkg-config         \
      libsystemd-dev     \
      libdbus-glib-1-dev \
      build-essential    \
      libelf-dev \
      libseccomp-dev
```

### Fedora, Centos, RHEL and related distributions

```console
$ sudo dnf install   \
      pkg-config     \
      systemd-devel  \
      dbus-devel     \
      elfutils-libelf-devel \
      libseccomp-devel
```

## Build

```console
$ git clone git@github.com:containers/youki.git
$ make build # or release-build
$ ./youki -h # you can get information about youki command
```

## Tutorial

### Create and run a container

Let's try to run a container that executes `sleep 30` with youki. This tutorial may need root permission.

```console
$ git clone git@github.com:containers/youki.git
$ make build # or release-build

$ 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.

```console
$ ../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:

```console
$ cd ..                                                # go back to the repository root
$ 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`.

### Rootless container

`youki` provides the ability to run containers as non-root user([rootless mode](https://docs.docker.com/engine/security/rootless/)). To run a container in rootless mode, we need to add some extra options in `config.json`, other steps are same with above:

```console
$ mkdir -p tutorial/rootfs
$ cd tutorial
# use docker to export busybox into the rootfs directory
$ docker export $(docker create busybox) | tar -C rootfs -xvf -

$ ../youki spec --rootless          # will generate a spec file named config.json with rootless mode
## Modify the `args` field as you like

$ ../youki run rootless-container   # will create and run a container with rootless mode
```

## Usage

Start the docker daemon.

```console
$ dockerd --experimental --add-runtime="youki=$(pwd)/target/x86_64-unknown-linux-gnu/debug/youki"
```

If you get an error like the below, that means your normal Docker daemon is running, and it needs to be stopped. Do that with your init system (i.e., with systemd, run `systemctl stop docker`, as root if necessary).

```
failed to start daemon: pid file found, ensure docker is not running or delete /var/run/docker.pid
```

Now repeat the command, which should start the docker daemon.

You can use youki in a different terminal to start the container.

```console
$ 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:

```console
$ systemctl start docker # might need root permission
```

### Integration Tests

Go and node-tap are required to run integration tests. See the [opencontainers/runtime-tools](https://github.com/opencontainers/runtime-tools) README for details.

```console
$ git submodule update --init --recursive
$ make oci-integration-test
```

### Setting up Vagrant

You can try youki on platforms other than Linux by using the Vagrantfile we have prepared. We have prepared two environments for vagrant, namely rootless mode and rootful mode

```console
$ git clone git@github.com:containers/youki.git
$ cd youki

# If you want to develop in rootless mode, and this is the default mode
$ vagrant up
$ vagrant ssh

# or if you want to develop in rootful mode
$ VAGRANT_VAGRANTFILE=Vagrantfile.root vagrant up
$ VAGRANT_VAGRANTFILE=Vagrantfile.root vagrant ssh

# in virtual machine
$ cd youki
$ make build # or release-build
```

# 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!

<a href="https://github.com/containers/youki/graphs/contributors">
  <img src="https://contributors-img.web.app/image?repo=containers/youki" />
</a>
