youki: A container runtime in Rust
youki is an implementation of the OCI runtime-spec in Rust, similar to runc.
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 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, 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 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 - 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. 
| Feature | Description | State |
|---|---|---|
| Docker | Running via Docker | |
| Podman | Running via Podman | It works, but cgroups isn't supported. WIP on #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 |
| Seccomp | Filtering system calls | |
| Hooks | Add custom processing during container creation | |
| Rootless | Running a container without root privileges | It works, but cgroups isn't supported. WIP on #77 |
| OCI Compliance | Compliance with OCI Runtime Spec | |
Design and implementation of youki
More details are in the works #14
Getting Started
Local build is only supported on linux. For other platforms, please use Vagrantfile that we prepared.
Requires
Dependencies
Debian, Ubuntu and related distributions
$ sudo apt-get install \
pkg-config \
libsystemd-dev \
libdbus-glib-1-dev \
build-essential \
libelf-dev \
libseccomp-dev
Fedora, Centos, RHEL and related distributions
$ sudo dnf install \
pkg-config \
systemd-devel \
dbus-devel \
elfutils-libelf-devel \
libseccomp-devel
Build
$ git clone [email protected]: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.
$ git clone [email protected]: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.
$ ../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.
"process": {
...
"args": [
"sleep", "30"
],
...
}
Then we can explore the lifecycle of a container:
$ 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.
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 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. We have prepared two environments for vagrant, namely rootless mode and rootful mode
$ git clone [email protected]: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
$ ./build.sh
Community
We also have an active Discord 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.
Thanks to all the people who already contributed!
![[Tracking Issue] Support for cgroups v1](https://avatars.githubusercontent.com/u/13010913?v=4)
![[WIP] Async Cgroups v1, tokio_uring](https://avatars.githubusercontent.com/u/623753?v=4)
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