Nydus Snapshotter

Nydus-snapshotter is a non-core sub-project of containerd.

Nydus snapshotter is an external plugin of containerd for Nydus image service which implements a chunk-based content-addressable filesystem on top of a called RAFS (Registry Acceleration File System) format that improves the current OCI image specification, in terms of container launching speed, image space, and network bandwidth efficiency, as well as data integrity with several runtime backends: FUSE, virtiofs and in-kernel EROFS.

Nydus supports lazy pulling feature since pulling image is one of the time-consuming steps in the container lifecycle. Lazy pulling here means a container can run even the image is partially available and necessary chunks of the image are fetched on-demand. Apart from that, Nydus also supports (e)Stargz lazy pulling directly WITHOUT any explicit conversion.

For more details about how to build Nydus container image, please refer to nydusify conversion tool and acceld.

Building

Just invoke make and check out the output executable binary ./bin/containerd-nydus-grpc

make

Integrate Nydus-snapshotter into Containerd

Containerd provides a general mechanism to exploit different types of snapshotters. Please ensure your containerd's version is 1.4.0 or above. Add Nydus as a proxy plugin into containerd's configuration file which may be located at /etc/containerd/config.toml.

# The `address` field specifies through which socket snapshotter and containerd communicate.
[proxy_plugins]
  [proxy_plugins.nydus]
    type = "snapshot"
    address = "/run/containerd-nydus/containerd-nydus-grpc.sock"

Restart your containerd service making the change take effect. Assume that your node is systemd based, restart the service as below:

systemctl restart containerd

Get Nydusd Binary

Find a suitable nydusd release for you from nydus releases page.

nydusd-fusedev is FUSE userspace daemon handling linux kernel FUSE requests from /dev/fuse frontend. nydusd-virtiofs is a virtiofs daemon handling guest kernel FUSE requests.

Configure Nydus

Nydus is configured by a json file which is required now. Since Nydus container images are likely stored in a registry, where auth has to be provided. Please follow instructions to configure nydus configure Nydus in order to make it work properly in your environment.

Start Nydus Snapshotter

Nydus-snapshotter is implemented as a proxy plugin (containerd-nydus-grpc) for containerd.

Assume your server systemd based, install nydus-snapshotter: Note: nydusd and nydus-image should be found from $PATH.

make install
systemctl restart containerd

Or you can start nydus-snapshotter manually.

# `nydusd-path` is the path to nydusd binary
# `address` is the domain socket that you configured in containerd configuration file
# `root` is the path to Nydus snapshotter
# `config-path` is the path to Nydus configuration file
$ ./containerd-nydus-grpc \
    --config-path /etc/nydusd-config.json \
    --shared-daemon \
    --log-level info \
    --root /var/lib/containerd/io.containerd.snapshotter.v1.nydus \
    --cache-dir /var/lib/nydus/cache \
    --address /run/containerd-nydus/containerd-nydus-grpc.sock \
    --nydusd-path /usr/local/bin/nydusd \
    --nydusimg-path /usr/local/bin/nydus-image \
    --log-to-stdout

You could append --enable-stargz to the command line above in order to enable (e)Stargz support.

Validate Nydus-snapshotter Setup

Utilize containerd's ctr CLI command to validate if nydus-snapshotter is set up successfully.

$ ctr -a /run/containerd/containerd.sock plugin ls
TYPE                            ID                       PLATFORMS      STATUS
io.containerd.snapshotter.v1    nydus                    -              ok

Quickly Start Container with Lazy Pulling

Start Container on Node

Containerd can start container with specified snapshotter, so nerdctl or ctr needs to specify the Nydus snapshotter when start container.

A CLI tool ctr-remote is alongside. Use Nydus ctr-remote to pull Nydus image or start container based on nydus image.

$ sudo ctr-remote image rpull ghcr.io/dragonflyoss/image-service/nginx:nydus-latest
fetching sha256:75002dfe... application/vnd.oci.image.manifest.v1+json
fetching sha256:5a42e21c... application/vnd.oci.image.config.v1+json
fetching sha256:eb1af2e1... application/vnd.oci.image.layer.v1.tar+gzip

# Start container by `ctr-remote`
$ sudo ctr-remote run --snapshotter nydus ghcr.io/dragonflyoss/image-service/nginx:nydus-latest awesome-nydus

# Start container by `nerdctl`
nerdctl --snapshotter nydus run ghcr.io/dragonflyoss/image-service/nginx:nydus-latest

In addition that, nerdctl can now directly pull Nydus or (e)Stargz images with Nydus snapshotter without ctr-remote involved:

# Start an eStargz container with Nydus snapshotter by `nerdctl`
nerdctl --snapshotter nydus run -it --rm ghcr.io/stargz-containers/fedora:35-esgz

Start Container in Kubernetes

NOTE: A potential drawback using CRI is that we can hardly specify snapshotter to nydus-snapshotter. So we have to change containerd's default snapshotter in its configuration file and enable snapshot annotations like below:

[plugins."io.containerd.grpc.v1.cri".containerd]
   snapshotter = "nydus"
   disable_snapshot_annotations = false

Use crictl to debug starting container via Kubernetes CRI. Dry run steps of using crictl can be found in documents.

Setup with nydus-snapshotter image

We can also use the nydus-snapshotter container image when we want to put Nydus stuffs inside a container. See the nydus-snapshotter exmple for how to setup and use it.

Community

Nydus aims to form a vendor-neutral opensource image distribution solution to all communities. Questions, bug reports, technical discussion, feature requests and contribution are always welcomed!

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