add nerdctl namespace ls

Also enable bash completion for `nerdctl --namespace`

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

Author: AkihiroSuda

README.md

@@ -190,6 +190,8 @@ It does not necessarily mean that the corresponding features are missing in cont
     - [:whale: nerdctl volume ls](#whale-nerdctl-volume-ls)
     - [:whale: nerdctl volume inspect](#whale-nerdctl-volume-inspect)
     - [:whale: nerdctl volume rm](#whale-nerdctl-volume-rm)
+  - [Namespace management](#namespace-management)
+    - [:nerd_face: nerdctl namespace ls](#nerd_face-nerdctl-namespace-ls)
   - [System](#system)
     - [:whale: nerdctl events](#whale-nerdctl-events)
     - [:whale: nerdctl info](#whale-nerdctl-info)
@@ -444,6 +446,13 @@ Display detailed information on one or more volumes
 ### :whale: nerdctl volume rm
 Remove one or more volumes
 
+## Namespace management
+
+### :nerd_face: nerdctl namespace ls
+List containerd namespaces such as "default", "moby", or "k8s.io".
+
+- `-q, --quiet`: Only display namespace names
+
 ## System
 ### :whale: nerdctl events
 Get real time events from the server.

main.go

@@ -18,6 +18,7 @@
 package main
 
 import (
+	"fmt"
 	"os"
 	"strings"
 
@@ -171,6 +172,7 @@ func newApp() *cli.App {
 		networkCommand,
 		volumeCommand,
 		systemCommand,
+		namespaceCommand,
 		// Internal
 		internalCommand,
 		// login
@@ -180,6 +182,7 @@ func newApp() *cli.App {
 		// Completion
 		completionCommand,
 	}
+	app.BashComplete = appBashComplete
 	return app
 }
 
@@ -188,3 +191,37 @@ type Category = string
 const (
 	CategoryManagement = Category("Management")
 )
+
+func appBashComplete(clicontext *cli.Context) {
+	if current, ok := isFlagCompletionContext(); ok {
+		switch current {
+		case "-n", "--namespace":
+			bashCompleteNamespaceNames(clicontext)
+			return
+		}
+	}
+	defaultBashComplete(clicontext)
+}
+
+func bashCompleteNamespaceNames(clicontext *cli.Context) {
+	if rootlessutil.IsRootlessParent() {
+		_ = rootlessutil.ParentMain()
+		return
+	}
+
+	client, ctx, cancel, err := newClient(clicontext)
+	if err != nil {
+		logrus.Warn(err)
+		return
+	}
+	defer cancel()
+	nsService := client.NamespaceService()
+	nsList, err := nsService.List(ctx)
+	if err != nil {
+		logrus.Warn(err)
+		return
+	}
+	for _, ns := range nsList {
+		fmt.Fprintln(clicontext.App.Writer, ns)
+	}
+}

namespace.go

@@ -0,0 +1,76 @@
+/*
+   Copyright (C) nerdctl authors.
+   Copyright (C) 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 main
+
+import (
+	"fmt"
+	"text/tabwriter"
+
+	"github.com/urfave/cli/v2"
+)
+
+var namespaceCommand = &cli.Command{
+	Name:        "namespace",
+	Usage:       "Manage containerd namespaces",
+	Description: "Unrelated to Linux namespaces and Kubernetes namespaces",
+	Category:    CategoryManagement,
+	Subcommands: []*cli.Command{
+		namespaceLsCommand,
+	},
+}
+
+var namespaceLsCommand = &cli.Command{
+	Name:    "ls",
+	Aliases: []string{"list"},
+	Usage:   "List containerd namespaces",
+	Action:  namespaceLsAction,
+	Flags: []cli.Flag{
+		&cli.BoolFlag{
+			Name:    "quiet",
+			Aliases: []string{"q"},
+			Usage:   "Only display namespace names",
+		},
+	},
+}
+
+func namespaceLsAction(clicontext *cli.Context) error {
+	client, ctx, cancel, err := newClient(clicontext)
+	if err != nil {
+		return err
+	}
+	defer cancel()
+
+	nsService := client.NamespaceService()
+	nsList, err := nsService.List(ctx)
+	if err != nil {
+		return err
+	}
+	if clicontext.Bool("q") {
+		for _, ns := range nsList {
+			fmt.Fprintln(clicontext.App.Writer, ns)
+		}
+		return nil
+	}
+
+	w := tabwriter.NewWriter(clicontext.App.Writer, 4, 8, 4, ' ', 0)
+	fmt.Fprintln(w, "NAME")
+	for _, ns := range nsList {
+		fmt.Fprintf(w, "%ss\n", ns)
+	}
+	return w.Flush()
+}