run: automatically generate a container name from image ref

e.g., `nerdctl run nginx` creates a container named "nginx-62edd".
See `pkg/referenceutil/referenceutil_test.go` for more examples.

The generated names are more meaningful than Docker/Podman-generated names such as "jolly_kepler".
However, the generated names MUST NOT be parsed.

The name can be unset by specifying `--name=""` explicitly.

Signed-off-by: Akihiro Suda <[email protected]>

Author: AkihiroSuda

cmd/nerdctl/run.go

@@ -51,6 +51,7 @@ import (
 	"github.com/containerd/nerdctl/pkg/netutil/nettype"
 	"github.com/containerd/nerdctl/pkg/platformutil"
 	"github.com/containerd/nerdctl/pkg/portutil"
+	"github.com/containerd/nerdctl/pkg/referenceutil"
 	"github.com/containerd/nerdctl/pkg/resolvconf"
 	"github.com/containerd/nerdctl/pkg/rootlessutil"
 	"github.com/containerd/nerdctl/pkg/strutil"
@@ -523,6 +524,14 @@ func createContainer(cmd *cobra.Command, ctx context.Context, client *containerd
 	if err != nil {
 		return nil, "", nil, err
 	}
+	if name == "" && !cmd.Flags().Changed("name") {
+		// Automatically set the container name, unless `--name=""` was explicitly specified.
+		var imageRef string
+		if ensuredImage != nil {
+			imageRef = ensuredImage.Ref
+		}
+		name = referenceutil.SuggestContainerName(imageRef, id)
+	}
 	if name != "" {
 		containerNameStore, err = namestore.New(dataStore, ns)
 		if err != nil {

pkg/referenceutil/referenceutil.go

@@ -18,6 +18,7 @@ package referenceutil
 
 import (
 	"fmt"
+	"path"
 	"strings"
 
 	refdocker "github.com/containerd/containerd/reference/docker"
@@ -35,8 +36,8 @@ type Reference interface {
 // If the ref has IPFS scheme or can be parsed as CID, it's parsed as an IPFS reference.
 // Otherwise it's parsed as a docker reference.
 func ParseAny(rawRef string) (Reference, error) {
-	if _, ref, err := ParseIPFSRefWithScheme(rawRef); err == nil {
-		return stringRef{ref}, nil
+	if scheme, ref, err := ParseIPFSRefWithScheme(rawRef); err == nil {
+		return stringRef{scheme: scheme, s: ref}, nil
 	}
 	if c, err := cid.Decode(rawRef); err == nil {
 		return c, nil
@@ -58,9 +59,39 @@ func ParseIPFSRefWithScheme(name string) (scheme, ref string, err error) {
 }
 
 type stringRef struct {
-	s string
+	scheme string
+	s      string
 }
 
 func (s stringRef) String() string {
 	return s.s
 }
+
+// SuggestContainerName generates a container name from name.
+// The result MUST NOT be parsed.
+func SuggestContainerName(rawRef, containerID string) string {
+	const shortIDLength = 5
+	if len(containerID) < shortIDLength {
+		panic(fmt.Errorf("got too short (< %d) container ID: %q", shortIDLength, containerID))
+	}
+	name := "untitled-" + containerID[:shortIDLength]
+	if rawRef != "" {
+		r, err := ParseAny(rawRef)
+		if err == nil {
+			switch rr := r.(type) {
+			case refdocker.Named:
+				if rrName := rr.Name(); rrName != "" {
+					imageNameBased := path.Base(rrName)
+					if imageNameBased != "" {
+						name = imageNameBased + "-" + containerID[:shortIDLength]
+					}
+				}
+			case cid.Cid:
+				name = "ipfs" + "-" + rr.String()[:shortIDLength] + "-" + containerID[:shortIDLength]
+			case stringRef:
+				name = rr.scheme + "-" + rr.s[:shortIDLength] + "-" + containerID[:shortIDLength]
+			}
+		}
+	}
+	return name
+}

pkg/referenceutil/referenceutil_test.go

@@ -0,0 +1,35 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package referenceutil
+
+import (
+	"testing"
+
+	"gotest.tools/v3/assert"
+)
+
+func TestSuggestContainerName(t *testing.T) {
+	const containerID = "16f6d167d4f4743e48affb86e7097222b7992b34a29dab5f8c10cd6a90cdd990"
+	assert.Equal(t, "alpine-16f6d", SuggestContainerName("alpine", containerID))
+	assert.Equal(t, "alpine-16f6d", SuggestContainerName("alpine:3.15", containerID))
+	assert.Equal(t, "alpine-16f6d", SuggestContainerName("docker.io/library/alpine:3.15", containerID))
+	assert.Equal(t, "alpine-16f6d", SuggestContainerName("docker.io/library/alpine:latest", containerID))
+	assert.Equal(t, "ipfs-bafkr-16f6d", SuggestContainerName("bafkreicq4dg6nkef5ju422ptedcwfz6kcvpvvhuqeykfrwq5krazf3muze", containerID))
+	assert.Equal(t, "ipfs-bafkr-16f6d", SuggestContainerName("ipfs://bafkreicq4dg6nkef5ju422ptedcwfz6kcvpvvhuqeykfrwq5krazf3muze", containerID))
+	assert.Equal(t, "untitled-16f6d", SuggestContainerName("invalid://alpine", containerID))
+	assert.Equal(t, "untitled-16f6d", SuggestContainerName("", containerID))
+}