188 lines
10 KiB
Markdown
188 lines
10 KiB
Markdown
# Lazy-pulling using Stargz Snapshotter
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| :zap: Requirement | nerdctl >= 0.0.1 |
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Lazy-pulling is a technique to running containers before completion of pulling the images.
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See https://github.com/containerd/stargz-snapshotter to learn further information.
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[](https://asciinema.org/a/378377)
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## Enable lazy-pulling for `nerdctl run`
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> **NOTE**
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> For rootless installation, see [`rootless.md`](./rootless.md#stargz-snapshotter)
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- Install Stargz plugin (`containerd-stargz-grpc`) from https://github.com/containerd/stargz-snapshotter
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- Add the following to `/etc/containerd/config.toml`:
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```toml
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[proxy_plugins]
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[proxy_plugins.stargz]
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type = "snapshot"
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address = "/run/containerd-stargz-grpc/containerd-stargz-grpc.sock"
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```
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- Launch `containerd` and `containerd-stargz-grpc`
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- Run `nerdctl` with `--snapshotter=stargz`
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```console
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# nerdctl --snapshotter=stargz run -it --rm ghcr.io/stargz-containers/fedora:30-esgz
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```
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For the list of pre-converted Stargz images, see https://github.com/containerd/stargz-snapshotter/blob/main/docs/pre-converted-images.md
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### Benchmark result (Dec 9, 2020)
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For running `python3 -c print("hi")`, eStargz with Stargz Snapshotter is 3-4 times faster than the legacy OCI with overlayfs snapshotter.
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Legacy OCI with overlayfs snapshotter:
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```console
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# time nerdctl --snapshotter=overlayfs run -it --rm ghcr.io/stargz-containers/python:3.7-org python3 -c 'print("hi")'
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ghcr.io/stargz-containers/python:3.7-org: resolved |++++++++++++++++++++++++++++++++++++++|
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index-sha256:6008006c63b0a6043a11ac151cee572e0c8676b4ba3130ff23deff5f5d711237: done |++++++++++++++++++++++++++++++++++++++|
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manifest-sha256:48eafda05f80010a6677294473d51a530e8f15375b6447195b6fb04dc2a30ce7: done |++++++++++++++++++++++++++++++++++++++|
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layer-sha256:f860607a6cd9751ac8db2f33cbc3ce1777a44eb3c04853e116763441a304fbf6: done |++++++++++++++++++++++++++++++++++++++|
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layer-sha256:96b2c1e36db5f5910f58da2ca4f9311b0690810c7107fb055ee1541498b5061f: done |++++++++++++++++++++++++++++++++++++++|
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layer-sha256:c495e8de12d26c9843a7a2bf8c68de1e5652e66d80d9bc869279f9af6f86736a: done |++++++++++++++++++++++++++++++++++++++|
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layer-sha256:33382189822a108b249cf3ccd234d04c3a8dfe7d593df19c751dcfab3675d5f2: done |++++++++++++++++++++++++++++++++++++++|
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config-sha256:94c9a318e47ab8a318582e2712bb495f92f17a7c1e50f13cc8a3e362c1b09290: done |++++++++++++++++++++++++++++++++++++++|
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layer-sha256:6eaa0b6b8562fb4a02e140ae53b3910fc4d0db6e68660390eaef993f42e21102: done |++++++++++++++++++++++++++++++++++++++|
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layer-sha256:adbdcbacafe93bf0791e49c8d3689bb78d9e60d02d384d4e14433aedae39f52c: done |++++++++++++++++++++++++++++++++++++++|
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layer-sha256:756975cb9c7e7933d824af9319b512dd72a50894232761d06ef3be59981df838: done |++++++++++++++++++++++++++++++++++++++|
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layer-sha256:d77915b4e630d47296770ce4cf481894885978072432456615172af463433cc5: done |++++++++++++++++++++++++++++++++++++++|
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layer-sha256:5f37a0a41b6b03489dd7de0aa2a79e369fd8b219bbc36b52f3f9790dc128e74b: done |++++++++++++++++++++++++++++++++++++++|
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elapsed: 41.9s total: 321.3 (7.7 MiB/s)
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hi
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real 0m51.754s
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user 0m2.687s
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sys 0m5.533s
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```
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eStargz with Stargz Snapshotter:
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```console
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# time nerdctl --snapshotter=stargz run -it --rm ghcr.io/stargz-containers/python:3.7-esgz python3 -c 'print("hi")'
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fetching sha256:2ea0dd96... application/vnd.oci.image.index.v1+json
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fetching sha256:9612ff73... application/vnd.docker.distribution.manifest.v2+json
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fetching sha256:34e5920e... application/vnd.docker.container.image.v1+json
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hi
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real 0m13.589s
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user 0m0.132s
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sys 0m0.158s
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```
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## Enable lazy-pulling for pulling base images during `nerdctl build`
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- Launch `buildkitd` with `--oci-worker-snapshotter=stargz` (or `--containerd-worker-snapshotter=stargz` if you use containerd worker)
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- Launch `nerdctl build`. No need to specify `--snapshotter` for `nerdctl`.
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## Building stargz images using `nerdctl build`
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```console
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$ nerdctl build -t example.com/foo .
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$ nerdctl image convert --estargz --oci example.com/foo example.com/foo:estargz
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$ nerdctl push example.com/foo:estargz
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```
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NOTE: `--estargz` should be specified in conjunction with `--oci`
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Stargz Snapshotter is not needed for building stargz images.
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## Tips for image conversion
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### Tips 1: Creating smaller eStargz images
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`nerdctl image convert` allows the following flags for optionally creating a smaller eStargz image.
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The result image requires stargz-snapshotter >= v0.13.0 for lazy pulling.
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- `--estargz-min-chunk-size`: The minimal number of bytes of data must be written in one gzip stream. If it's > 0, multiple files and chunks can be written into one gzip stream. Smaller number of gzip header and smaller size of the result blob can be expected. `--estargz-min-chunk-size=0` produces normal eStargz.
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- `--estargz-external-toc`: Separate TOC JSON metadata into another image (called "TOC image"). The result eStargz doesn't contain TOC so we can expect a smaller size than normal eStargz. This is an [experimental](./experimental.md) feature.
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#### `--estargz-min-chunk-size` usage
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conversion:
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```console
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# nerdctl image convert --oci --estargz --estargz-min-chunk-size=50000 ghcr.io/stargz-containers/ubuntu:22.04 registry2:5000/ubuntu:22.04-chunk50000
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# nerdctl image ls
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REPOSITORY TAG IMAGE ID CREATED PLATFORM SIZE BLOB SIZE
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ghcr.io/stargz-containers/ubuntu 22.04 20fa2d7bb4de 14 seconds ago linux/amd64 83.4 MiB 29.0 MiB
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registry2:5000/ubuntu 22.04-chunk50000 562e09e1b3c1 2 seconds ago linux/amd64 0.0 B 29.2 MiB
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# nerdctl push --insecure-registry registry2:5000/ubuntu:22.04-chunk50000
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```
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Pull it lazily:
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```console
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# nerdctl pull --snapshotter=stargz --insecure-registry registry2:5000/ubuntu:22.04-chunk50000
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# mount | grep "stargz on"
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stargz on /var/lib/containerd-stargz-grpc/snapshotter/snapshots/1/fs type fuse.rawBridge (rw,nodev,relatime,user_id=0,group_id=0,allow_other)
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```
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#### `--estargz-external-toc` usage
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convert:
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```console
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# nerdctl image convert --oci --estargz --estargz-external-toc ghcr.io/stargz-containers/ubuntu:22.04 registry2:5000/ubuntu:22.04-ex
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INFO[0005] Extra image(0) registry2:5000/ubuntu:22.04-ex-esgztoc
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sha256:3059dd5d9c404344e0b7c43d9782de8cae908531897262b7772103a0b585bbee
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# nerdctl images
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REPOSITORY TAG IMAGE ID CREATED PLATFORM SIZE BLOB SIZE
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ghcr.io/stargz-containers/ubuntu 22.04 20fa2d7bb4de 9 seconds ago linux/amd64 83.4 MiB 29.0 MiB
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registry2:5000/ubuntu 22.04-ex 3059dd5d9c40 1 second ago linux/amd64 0.0 B 30.8 MiB
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registry2:5000/ubuntu 22.04-ex-esgztoc 18c042b6eb8b 1 second ago linux 0.0 B 151.3 KiB
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```
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Then push eStargz(`registry2:5000/ubuntu:22.04-ex`) and TOC image(`registry2:5000/ubuntu:22.04-ex-esgztoc`) to the same registry (`registry2` is used in this example but you can use arbitrary registries):
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```console
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# nerdctl push --insecure-registry registry2:5000/ubuntu:22.04-ex
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# nerdctl push --insecure-registry registry2:5000/ubuntu:22.04-ex-esgztoc
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```
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Pull it lazily:
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```console
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# nerdctl pull --insecure-registry --snapshotter=stargz registry2:5000/ubuntu:22.04-ex
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```
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Stargz Snapshotter automatically refers to the TOC image on the same registry.
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##### optional `--estargz-keep-diff-id` flag for conversion without changing layer diffID
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`nerdctl image convert` supports optional flag `--estargz-keep-diff-id` specified with `--estargz-external-toc`.
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This converts an image to eStargz without changing the diffID (uncompressed digest) so even eStargz-agnostic gzip decompressor (e.g. gunzip) can restore the original tar blob.
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```console
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# nerdctl image convert --oci --estargz --estargz-external-toc --estargz-keep-diff-id ghcr.io/stargz-containers/ubuntu:22.04 registry2:5000/ubuntu:22.04-ex-keepdiff
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# nerdctl push --insecure-registry registry2:5000/ubuntu:22.04-ex-keepdiff
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# nerdctl push --insecure-registry registry2:5000/ubuntu:22.04-ex-keepdiff-esgztoc
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# crane --insecure blob registry2:5000/ubuntu:22.04-ex-keepdiff@sha256:2dc39ba059dcd42ade30aae30147b5692777ba9ff0779a62ad93a74de02e3e1f | jq -r '.rootfs.diff_ids[]'
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sha256:7f5cbd8cc787c8d628630756bcc7240e6c96b876c2882e6fc980a8b60cdfa274
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# crane blob ghcr.io/stargz-containers/ubuntu:22.04@sha256:2dc39ba059dcd42ade30aae30147b5692777ba9ff0779a62ad93a74de02e3e1f | jq -r '.rootfs.diff_ids[]'
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sha256:7f5cbd8cc787c8d628630756bcc7240e6c96b876c2882e6fc980a8b60cdfa274
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```
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### Tips 2: Using zstd instead of gzip (a.k.a. zstd:chunked)
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You can use zstd compression with lazy pulling support (a.k.a zstd:chunked) instead of gzip.
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- Pros
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- [Faster](https://github.com/facebook/zstd/tree/v1.5.2#benchmarks) compression/decompression.
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- Cons
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- Old tools might not support. And unsupported by some tools yet.
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- zstd supported by OCI Image Specification is still under rc (2022/11). will be added to [v1.1.0](https://github.com/opencontainers/image-spec/commit/1a29e8675a64a5cdd2d93b6fa879a82d9a4d926a).
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- zstd supported by [docker >=v23.0.0](https://github.com/moby/moby/releases/tag/v23.0.0).
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- zstd supported by [containerd >= v1.5](https://github.com/containerd/containerd/releases/tag/v1.5.0).
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- `min-chunk-size`, `external-toc` (described in Tips 1) are unsupported yet.
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```console
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$ nerdctl build -t example.com/foo .
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$ nerdctl image convert --zstdchunked --oci example.com/foo example.com/foo:zstdchunked
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$ nerdctl push example.com/foo:zstdchunked
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```
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