Nydus Snapshotter

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

Pulling and unpacking OCI container image are time consuming when start a container. Nydus is a vendor-neutral project aiming at mitigating the problem. It designs a new container image oriented and optimized file system format with capability of on-demand read. For instructions on how to build nydus container image, please refer to nydusify conversion tool.

Building

Just invoke make and find output 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 beyond 1.4.0.
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. Because nydus container images are likely stored in a registry, where auth has to be provided.
Please follow instructions to configure nydus configure nydus making it work properly in your environment.

Start Nydus Snapshotter

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

A example of starting nydus-snapshotter:

# `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/containerd-nydus-grpc.sock \
    --nydusd-path /usr/local/bin/nydusd \
    --nydusimg-path /usr/local/bin/nydus-image \
    --log-to-stdout

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 legacy method like 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`
$ sudo ctr-remote run --snapshotter nydus ghcr.io/dragonflyoss/image-service/nginx:nydus-latest

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

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 like below:

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

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

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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GitHub

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