youki: A container runtime in Rust

youki is an implementation of the OCI runtime-spec in Rust, similar to runc.
Your ideas are welcome here.

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 about the benchmark

  • A command used for the benchmark

    $ 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

    $ ./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
    

• 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
Containerd	Running via Containerd	✅
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 #230
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/

Getting Started

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

Requires

• Rust(See here), edition 2021
• linux kernel ≥ 5.3

Dependencies

Debian, Ubuntu and related distributions

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

Fedora, Centos, RHEL and related distributions

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

Build

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

Tutorial

Requires

• Docker(See here)

Create and run a container

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

$ git clone git@github.com:containers/youki.git
$ cd youki
$ make youki-dev # or youki-release

$ 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.

Rootless container

youki provides the ability to run containers as non-root user(rootless mode). To run a container in rootless mode, we need to add some extra options in config.json, other steps are same with above:

$ 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.

$ dockerd --experimental --add-runtime="youki=$(pwd)/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.

$ 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 Tests

Go and node-tap are required to run integration tests. See the opencontainers/runtime-tools README for details.

$ git submodule update --init --recursive
$ make oci-tests

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 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 youki-dev # or youki-release

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!