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Refactor image management to use transfer service #4583

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c40fda5
Refactor image management to use transfer service
ChengyuZhu6 Nov 5, 2025
b4c6c8f
configure containerd config with remote snapshotter
ChengyuZhu6 Nov 5, 2025
7d8ab7c
Support legacy push/pull for containerd 1.7.x
ChengyuZhu6 Nov 26, 2025
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9 changes: 9 additions & 0 deletions Dockerfile.d/etc_containerd_config.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -5,3 +5,12 @@ version = 2
[proxy_plugins.stargz]
type = "snapshot"
address = "/run/containerd-stargz-grpc/containerd-stargz-grpc.sock"
[proxy_plugins.stargz.exports]
root = "/var/lib/containerd-stargz-grpc/"
enable_remote_snapshot_annotations = "true"
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "overlayfs"
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@AkihiroSuda AkihiroSuda Nov 28, 2025

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What happens if this config is not specified?
i.e., what happens with the default config?

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@ChengyuZhu6 ChengyuZhu6 Nov 28, 2025

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By default, it would be

[[plugins."io.containerd.transfer.v1.local".unpack_config]]
  platform = "linux/amd64"(matches the host's OS/Architecture)
  snapshotter = "overlayfs" 
  differ = "walking"

[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "stargz"
18 changes: 18 additions & 0 deletions Dockerfile.d/test-integration-etc_containerd_config.toml
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Expand Up @@ -5,8 +5,26 @@ version = 2
[proxy_plugins.stargz]
type = "snapshot"
address = "/run/containerd-stargz-grpc/containerd-stargz-grpc.sock"
[proxy_plugins.stargz.exports]
root = "/var/lib/containerd-stargz-grpc/"
enable_remote_snapshot_annotations = "true"

# Enable soci snapshotter
[proxy_plugins.soci]
type = "snapshot"
address = "/run/soci-snapshotter-grpc/soci-snapshotter-grpc.sock"
[proxy_plugins.soci.exports]
root = "/var/lib/soci-snapshotter-grpc"
enable_remote_snapshot_annotations = "true"

[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "overlayfs"

[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "soci"

[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "stargz"
9 changes: 9 additions & 0 deletions Dockerfile.d/test-integration-rootless.sh
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Expand Up @@ -53,6 +53,15 @@ else
[proxy_plugins."stargz"]
type = "snapshot"
address = "/run/user/$(id -u)/containerd-stargz-grpc/containerd-stargz-grpc.sock"
[proxy_plugins.stargz.exports]
root = "/home/rootless/.local/share/containerd-stargz-grpc/"
enable_remote_snapshot_annotations = "true"
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "overlayfs"
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "stargz"
EOF
systemctl --user restart containerd.service
containerd-rootless-setuptool.sh -- install-ipfs --init --offline # offline ipfs daemon for testing
Expand Down
1 change: 1 addition & 0 deletions README.md
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Expand Up @@ -287,6 +287,7 @@ Advanced features:

- [`./docs/stargz.md`](./docs/stargz.md): Lazy-pulling using Stargz Snapshotter
- [`./docs/nydus.md`](./docs/nydus.md): Lazy-pulling using Nydus Snapshotter
- [`./docs/soci.md`](./docs/soci.md): Lazy-pulling using SOCI Snapshotter
- [`./docs/overlaybd.md`](./docs/overlaybd.md): Lazy-pulling using OverlayBD Snapshotter
- [`./docs/ocicrypt.md`](./docs/ocicrypt.md): Running encrypted images
- [`./docs/gpu.md`](./docs/gpu.md): Using GPUs inside containers
Expand Down
2 changes: 1 addition & 1 deletion cmd/nerdctl/container/container_run_test.go
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Expand Up @@ -786,7 +786,7 @@ func TestRunFromOCIArchive(t *testing.T) {
tarPath := fmt.Sprintf("%s/%s.tar", buildCtx, imageName)

base.Cmd("build", "--tag", tag, fmt.Sprintf("--output=type=oci,dest=%s", tarPath), buildCtx).AssertOK()
base.Cmd("run", "--rm", fmt.Sprintf("oci-archive://%s", tarPath)).AssertOutContainsAll(fmt.Sprintf("Loaded image: %s", tag), sentinel)
base.Cmd("run", "--rm", fmt.Sprintf("oci-archive://%s", tarPath)).AssertOutContainsAll(tag, sentinel)
}

func TestRunDomainname(t *testing.T) {
Expand Down
5 changes: 2 additions & 3 deletions cmd/nerdctl/image/image_load_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,6 @@
package image

import (
"fmt"
"os"
"path/filepath"
"strings"
Expand Down Expand Up @@ -61,7 +60,7 @@ func TestLoadStdinFromPipe(t *testing.T) {
identifier := data.Identifier()
return &test.Expected{
Output: expect.All(
expect.Contains(fmt.Sprintf("Loaded image: %s:latest", identifier)),
expect.Contains(identifier),
func(stdout string, t tig.T) {
assert.Assert(t, strings.Contains(helpers.Capture("images"), identifier))
},
Expand Down Expand Up @@ -107,7 +106,7 @@ func TestLoadQuiet(t *testing.T) {
Expected: func(data test.Data, helpers test.Helpers) *test.Expected {
return &test.Expected{
Output: expect.All(
expect.Contains(fmt.Sprintf("Loaded image: %s:latest", data.Identifier())),
expect.Contains(data.Identifier()),
expect.DoesNotContain("Loading layer"),
),
}
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5 changes: 5 additions & 0 deletions docs/nydus.md
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Expand Up @@ -15,6 +15,11 @@ Nydus snapshotter is a remote snapshotter plugin of containerd for [Nydus](https
[proxy_plugins.nydus]
type = "snapshot"
address = "/run/containerd-nydus-grpc/containerd-nydus-grpc.sock"

# Optional: Configure nydus for image unpacking (allows automatic snapshotter selection)
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "nydus"
```

- Launch `containerd` and `containerd-nydus-grpc`
Expand Down
5 changes: 5 additions & 0 deletions docs/overlaybd.md
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Expand Up @@ -17,6 +17,11 @@ See https://github.com/containerd/accelerated-container-image to learn further i
[proxy_plugins.overlaybd]
type = "snapshot"
address = "/run/overlaybd-snapshotter/overlaybd.sock"

# Optional: Configure overlaybd for image unpacking (allows automatic snapshotter selection)
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "overlaybd"
```

- Launch `containerd` and `overlaybd-snapshotter`
Expand Down
10 changes: 10 additions & 0 deletions docs/rootless.md
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Expand Up @@ -73,6 +73,11 @@ Then, add the following config to `~/.config/containerd/config.toml`, and run `s
type = "snapshot"
# NOTE: replace "1000" with your actual UID
address = "/run/user/1000/containerd-fuse-overlayfs.sock"

# Optional: Configure fuse-overlayfs for image unpacking (allows automatic snapshotter selection)
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "fuse-overlayfs"
```

The snapshotter can be specified as `$CONTAINERD_SNAPSHOTTER`.
Expand All @@ -98,6 +103,11 @@ Then, add the following config to `~/.config/containerd/config.toml` and run `sy
type = "snapshot"
# NOTE: replace "1000" with your actual UID
address = "/run/user/1000/containerd-stargz-grpc/containerd-stargz-grpc.sock"

# Optional: Configure stargz for image unpacking (allows automatic snapshotter selection)
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "stargz"
```

The snapshotter can be specified as `$CONTAINERD_SNAPSHOTTER`.
Expand Down
5 changes: 5 additions & 0 deletions docs/soci.md
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Expand Up @@ -30,6 +30,11 @@ For detailed information about the differences between v1 and v2, see the [SOCI
[proxy_plugins.soci]
type = "snapshot"
address = "/run/soci-snapshotter-grpc/soci-snapshotter-grpc.sock"

# Optional: Configure soci for image unpacking (allows automatic snapshotter selection)
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "soci"
```

- Launch `containerd` and `soci-snapshotter-grpc`
Expand Down
5 changes: 5 additions & 0 deletions docs/stargz.md
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Expand Up @@ -22,6 +22,11 @@ See https://github.com/containerd/stargz-snapshotter to learn further informatio
[proxy_plugins.stargz]
type = "snapshot"
address = "/run/containerd-stargz-grpc/containerd-stargz-grpc.sock"

# Optional: Configure stargz for image unpacking (allows automatic snapshotter selection)
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "stargz"
```

- Launch `containerd` and `containerd-stargz-grpc`
Expand Down
18 changes: 18 additions & 0 deletions extras/rootless/containerd-rootless-setuptool.sh
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Expand Up @@ -404,6 +404,15 @@ cmd_entrypoint_install_fuse_overlayfs() {
[proxy_plugins."fuse-overlayfs"]
type = "snapshot"
address = "${XDG_RUNTIME_DIR}/containerd-fuse-overlayfs.sock"
[proxy_plugins."fuse-overlayfs".exports]
root = "${XDG_DATA_HOME}/containerd-fuse-overlayfs/"
enable_remote_snapshot_annotations = "true"
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "fuse-overlayfs"
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "overlayfs"
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@AkihiroSuda AkihiroSuda Nov 28, 2025

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Not a fan of complicating the config.
What happens if these lines are missing?
ctr doesn't need them AFAICS?

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@ChengyuZhu6 ChengyuZhu6 Nov 28, 2025

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By default, it would be

[[plugins."io.containerd.transfer.v1.local".unpack_config]]
  platform = "linux/amd64"(matches the host's OS/Architecture)
  snapshotter = "overlayfs" 
  differ = "walking"

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@ChengyuZhu6 ChengyuZhu6 Nov 28, 2025

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This config is required to specify which snapshotter the transfer service should use when unpacking images. We define multiple unpack targets:

  • overlayfs for standard OCI images
  • stargz / soci for lazy-pulling support

Without this, containerd defaults to basic unpacking and won't leverage stargz/soci snapshotters needed for lazy-pulling.

And if we only configure stargz in unpack_config, then all images would be forced to use the stargz snapshotter during transfer/unpacking, even standard OCI images that don't support lazy-pulling.

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@AkihiroSuda AkihiroSuda Dec 2, 2025

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Can you add that as comment lines, and update the relevant docs?
What about soci, nydus, etc?

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@ChengyuZhu6 ChengyuZhu6 Dec 2, 2025

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Sure.

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@ChengyuZhu6 ChengyuZhu6 Dec 3, 2025

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Done.

### END ###
EOT
INFO "Set \`export CONTAINERD_SNAPSHOTTER=\"fuse-overlayfs\"\` to use the fuse-overlayfs snapshotter."
Expand Down Expand Up @@ -449,6 +458,15 @@ cmd_entrypoint_install_stargz() {
[proxy_plugins."stargz"]
type = "snapshot"
address = "${XDG_RUNTIME_DIR}/containerd-stargz-grpc/containerd-stargz-grpc.sock"
[proxy_plugins.stargz.exports]
root = "${XDG_DATA_HOME}/containerd-stargz-grpc/"
enable_remote_snapshot_annotations = "true"
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "stargz"
[[plugins."io.containerd.transfer.v1.local".unpack_config]]
platform = "linux"
snapshotter = "overlayfs"
### END ###
EOT
INFO "Set \`export CONTAINERD_SNAPSHOTTER=\"stargz\"\` to use the stargz snapshotter."
Expand Down
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