Add "k0sctl exec" (alias ssh) to open a remote console by kke · Pull Request #1027 · k0sproject/k0sctl

kke · 2026-02-12T11:33:27Z

Likely works as base for #985

Signed-off-by: Kimmo Lehto <klehto@mirantis.com>

Copilot

Pull request overview

Adds a new k0sctl exec CLI command (alias ssh) to open an interactive remote shell or run a non-interactive command across one or more hosts defined in the k0sctl config, which can serve as a building block for future “fetch logs” workflows (e.g., #985).

Changes:

Register a new top-level exec command in the root CLI.
Implement k0sctl exec / k0sctl ssh with host filtering (--address, --role, --first) and optional parallel execution (--parallel).
Add command/stdin forwarding and prefixed multi-host output formatting.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
cmd/root.go	Registers the new `exec` command in the CLI command list.
cmd/exec.go	Implements the new `exec`/`ssh` command, including host selection, connect/exec logic, and output handling.

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

Copilot · 2026-02-12T11:38:48Z

cmd/exec.go

+		hosts := cfg.Spec.Hosts
+
+		if addresses := ctx.StringSlice("address"); len(addresses) > 0 {
+			hosts = hosts.Filter(func(h *cluster.Host) bool {
+				for _, a := range addresses {
+					if h.Address() == a {
+						return true
+					}
+				}
+				return false
+			})
+		}
+		if role := ctx.String("role"); role != "" {
+			hosts = hosts.WithRole(role)
+		}
+		if ctx.Bool("first") && len(hosts) > 0 {
+			hosts = hosts[:1]
+		}
+
+		if len(hosts) == 0 {
+			return fmt.Errorf("no hosts matched the given filters")
+		}


This command introduces new host filtering/execution behavior (address/role/first/parallel, interactive single-host restriction, stdin forwarding), but there are no unit tests covering these cases. Adding cmd-level tests similar to apply/init would help prevent regressions (e.g., filter matching, error messages for 0/many hosts, and parallel vs sequential execution paths).

Copilot · 2026-02-12T11:38:48Z

cmd/exec.go

+		defer func() {
+			_ = hosts.Each(ctx.Context, func(_ context.Context, h *cluster.Host) error {
+				h.Disconnect()
+				return nil
+			})
+		}()


The deferred disconnect uses ctx.Context, so if the command context is canceled (timeout/Ctrl-C), hosts.Each will stop early and some hosts may never be disconnected. Use a non-canceling context for cleanup (e.g., context.WithoutCancel(ctx.Context) or context.Background()) so all connections are reliably closed.

Copilot · 2026-02-12T11:38:48Z

cmd/exec.go

+		if err := hosts.ParallelEach(ctx.Context, func(_ context.Context, h *cluster.Host) error {
+			log.Debugf("connecting to %s", h.Address())
+			if err := h.Connect(); err != nil {
+				return fmt.Errorf("failed to connect to %s: %w", h.Address(), err)
+			}
+			return nil
+		}); err != nil {
+			return err
+		}


Host connections are always established via hosts.ParallelEach, which spawns one goroutine per host with no concurrency limit. This ignores the command’s --parallel flag and can overwhelm SSH/WinRM limits on large clusters. Consider connecting sequentially when --parallel is false, and/or using BatchedParallelEach with a configurable concurrency limit (reusing the existing --concurrency flag or config Spec.Options.Concurrency.Limit).

cmd/exec.go

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

Copilot · 2026-02-12T13:24:57Z

cmd/exec.go

+var execCommand = &cli.Command{
+	Name:      "exec",
+	Aliases:   []string{"ssh"},
+	Usage:     "Open a remote terminal or run a command on hosts",
+	ArgsUsage: "[-- COMMAND ...]",
+	Flags: []cli.Flag{
+		configFlag,
+		&cli.StringSliceFlag{
+			Name:    "address",
+			Usage:   "Target host address (can be given multiple times)",
+			Aliases: []string{"a"},
+		},
+		&cli.StringFlag{
+			Name:    "role",
+			Usage:   "Filter hosts by role",
+			Aliases: []string{"r"},
+		},
+		&cli.BoolFlag{
+			Name:    "first",
+			Usage:   "Use only the first matching host",
+			Aliases: []string{"f"},
+		},
+		&cli.BoolFlag{
+			Name:    "parallel",
+			Usage:   "Run command on hosts in parallel",
+			Aliases: []string{"p"},
+		},
+		debugFlag,
+		traceFlag,
+		redactFlag,
+	},


The command is missing a Usage description. Other commands in the codebase provide a concise description of what the command does. Consider adding a brief description similar to how other commands document their purpose, for example: "Usage: "Open a remote terminal or run a command on cluster hosts","

Copilot · 2026-02-12T13:24:57Z

cmd/exec.go

+var execCommand = &cli.Command{
+	Name:      "exec",
+	Aliases:   []string{"ssh"},
+	Usage:     "Open a remote terminal or run a command on hosts",
+	ArgsUsage: "[-- COMMAND ...]",
+	Flags: []cli.Flag{
+		configFlag,
+		&cli.StringSliceFlag{
+			Name:    "address",
+			Usage:   "Target host address (can be given multiple times)",
+			Aliases: []string{"a"},
+		},
+		&cli.StringFlag{
+			Name:    "role",
+			Usage:   "Filter hosts by role",
+			Aliases: []string{"r"},
+		},
+		&cli.BoolFlag{
+			Name:    "first",
+			Usage:   "Use only the first matching host",
+			Aliases: []string{"f"},
+		},
+		&cli.BoolFlag{
+			Name:    "parallel",
+			Usage:   "Run command on hosts in parallel",
+			Aliases: []string{"p"},
+		},
+		debugFlag,
+		traceFlag,
+		redactFlag,
+	},
+	Before: actions(initLogging, initConfig),
+	Action: func(ctx *cli.Context) error {
+		cfg, err := readConfig(ctx)
+		if err != nil {
+			return err
+		}
+
+		hosts := cfg.Spec.Hosts
+
+		if addresses := ctx.StringSlice("address"); len(addresses) > 0 {
+			hosts = hosts.Filter(func(h *cluster.Host) bool {
+				for _, a := range addresses {
+					if h.Address() == a {
+						return true
+					}
+				}
+				return false
+			})
+		}
+		if role := ctx.String("role"); role != "" {
+			hosts = hosts.WithRole(role)
+		}
+		if ctx.Bool("first") && len(hosts) > 0 {
+			hosts = hosts[:1]
+		}
+
+		if len(hosts) == 0 {
+			return fmt.Errorf("no hosts matched the given filters")
+		}
+
+		args := ctx.Args().Slice()
+		var command string
+		if len(args) > 0 {
+			quoted := make([]string, len(args))
+			for i, a := range args {
+				quoted[i] = shellescape.Quote(a)
+			}
+			command = strings.Join(quoted, " ")
+		}
+
+		if command == "" && len(hosts) > 1 {
+			return fmt.Errorf("interactive shell requires a single host, %d hosts matched (use --first to select the first one)", len(hosts))
+		}
+
+		if err := hosts.ParallelEach(ctx.Context, func(_ context.Context, h *cluster.Host) error {
+			log.Debugf("connecting to %s", h.Address())
+			if err := h.Connect(); err != nil {
+				return fmt.Errorf("failed to connect to %s: %w", h.Address(), err)
+			}
+			return nil
+		}); err != nil {
+			return err
+		}
+		defer func() {
+			_ = hosts.Each(ctx.Context, func(_ context.Context, h *cluster.Host) error {
+				h.Disconnect()
+				return nil
+			})
+		}()
+
+		if command == "" {
+			return hosts[0].ExecInteractive("")
+		}
+
+		var stdinData string
+		if f, ok := ctx.App.Reader.(*os.File); ok {
+			if stat, err := f.Stat(); err == nil && (stat.Mode()&os.ModeCharDevice) == 0 {
+				data, err := io.ReadAll(f)
+				if err != nil {
+					return fmt.Errorf("failed to read stdin: %w", err)
+				}
+				stdinData = string(data)
+			}
+		}
+
+		multiHost := len(hosts) > 1
+		var mu sync.Mutex
+		execOnHost := func(_ context.Context, h *cluster.Host) error {
+			var opts []exec.Option
+			if stdinData != "" {
+				opts = append(opts, exec.Stdin(stdinData))
+			}
+
+			output, err := h.ExecOutput(command, opts...)
+			if output != "" {
+				mu.Lock()
+				if multiHost {
+					for _, line := range strings.Split(strings.TrimRight(output, "\n"), "\n") {
+						fmt.Fprintf(ctx.App.Writer, "%s: %s\n", h.Address(), line)
+					}
+				} else {
+					fmt.Fprint(ctx.App.Writer, output)
+					if !strings.HasSuffix(output, "\n") {
+						fmt.Fprintln(ctx.App.Writer)
+					}
+				}
+				mu.Unlock()
+			}
+			if err != nil {
+				return fmt.Errorf("%s: command failed: %w", h.Address(), err)
+			}
+			return nil
+		}
+
+		if ctx.Bool("parallel") {
+			return hosts.ParallelEach(ctx.Context, execOnHost)
+		}
+		return hosts.Each(ctx.Context, execOnHost)
+	},
+}


There is no test coverage for the new exec command. Given that the repository has test coverage for other commands (apply_test.go, init_test.go, flags_test.go), the exec command should also have unit tests to verify its functionality, particularly around host filtering logic, command execution paths, and error handling.

Copilot · 2026-02-12T13:24:58Z

cmd/exec.go

+		},
+		&cli.BoolFlag{
+			Name:    "parallel",
+			Usage:   "Run command on hosts in parallel",


The parallel execution flag is ignored when running in interactive mode (when no command is provided), but this is not documented in the flag's Usage text. Consider adding a note to the Usage that indicates this flag only applies when running a command, not in interactive mode, to avoid user confusion.

Suggested change

Usage: "Run command on hosts in parallel",

Usage: "Run command on hosts in parallel (only applies when a command is provided, not in interactive mode)",

Copilot · 2026-02-12T13:24:58Z

cmd/exec.go

+	Action: func(ctx *cli.Context) error {
+		cfg, err := readConfig(ctx)
+		if err != nil {
+			return err
+		}
+
+		hosts := cfg.Spec.Hosts
+
+		if addresses := ctx.StringSlice("address"); len(addresses) > 0 {
+			hosts = hosts.Filter(func(h *cluster.Host) bool {
+				for _, a := range addresses {
+					if h.Address() == a {
+						return true
+					}
+				}
+				return false
+			})
+		}
+		if role := ctx.String("role"); role != "" {
+			hosts = hosts.WithRole(role)
+		}
+		if ctx.Bool("first") && len(hosts) > 0 {
+			hosts = hosts[:1]
+		}
+
+		if len(hosts) == 0 {
+			return fmt.Errorf("no hosts matched the given filters")
+		}
+
+		args := ctx.Args().Slice()
+		var command string
+		if len(args) > 0 {
+			quoted := make([]string, len(args))
+			for i, a := range args {
+				quoted[i] = shellescape.Quote(a)
+			}
+			command = strings.Join(quoted, " ")
+		}
+
+		if command == "" && len(hosts) > 1 {
+			return fmt.Errorf("interactive shell requires a single host, %d hosts matched (use --first to select the first one)", len(hosts))
+		}
+
+		if err := hosts.ParallelEach(ctx.Context, func(_ context.Context, h *cluster.Host) error {
+			log.Debugf("connecting to %s", h.Address())
+			if err := h.Connect(); err != nil {
+				return fmt.Errorf("failed to connect to %s: %w", h.Address(), err)
+			}
+			return nil
+		}); err != nil {
+			return err
+		}
+		defer func() {
+			_ = hosts.Each(ctx.Context, func(_ context.Context, h *cluster.Host) error {
+				h.Disconnect()
+				return nil
+			})
+		}()
+
+		if command == "" {
+			return hosts[0].ExecInteractive("")
+		}
+
+		var stdinData string
+		if f, ok := ctx.App.Reader.(*os.File); ok {
+			if stat, err := f.Stat(); err == nil && (stat.Mode()&os.ModeCharDevice) == 0 {
+				data, err := io.ReadAll(f)
+				if err != nil {
+					return fmt.Errorf("failed to read stdin: %w", err)
+				}
+				stdinData = string(data)
+			}
+		}
+
+		multiHost := len(hosts) > 1
+		var mu sync.Mutex
+		execOnHost := func(_ context.Context, h *cluster.Host) error {
+			var opts []exec.Option
+			if stdinData != "" {
+				opts = append(opts, exec.Stdin(stdinData))
+			}
+
+			output, err := h.ExecOutput(command, opts...)
+			if output != "" {
+				mu.Lock()
+				if multiHost {
+					for _, line := range strings.Split(strings.TrimRight(output, "\n"), "\n") {
+						fmt.Fprintf(ctx.App.Writer, "%s: %s\n", h.Address(), line)
+					}
+				} else {
+					fmt.Fprint(ctx.App.Writer, output)
+					if !strings.HasSuffix(output, "\n") {
+						fmt.Fprintln(ctx.App.Writer)
+					}
+				}
+				mu.Unlock()
+			}
+			if err != nil {
+				return fmt.Errorf("%s: command failed: %w", h.Address(), err)
+			}
+			return nil
+		}
+
+		if ctx.Bool("parallel") {
+			return hosts.ParallelEach(ctx.Context, execOnHost)
+		}
+		return hosts.Each(ctx.Context, execOnHost)
+	},


Error messages should include the log file location for consistency with other commands that use initLogging. Commands like apply, backup, reset, and kubeconfig all include "log file saved to" in their error messages. Consider wrapping major errors with a reference to the log file location using ctx.Context.Value(ctxLogFileKey{}).(string).

Add "k0sctl exec" (alias ssh) to open a remote console

c3e3c60

Signed-off-by: Kimmo Lehto <klehto@mirantis.com>

kke requested a review from Copilot February 12, 2026 11:34

Copilot started reviewing on behalf of kke February 12, 2026 11:35 View session

Copilot AI reviewed Feb 12, 2026

View reviewed changes

kke requested a review from Copilot February 12, 2026 13:19

Copilot started reviewing on behalf of kke February 12, 2026 13:20 View session

Copilot AI reviewed Feb 12, 2026

View reviewed changes

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Add "k0sctl exec" (alias ssh) to open a remote console#1027

Add "k0sctl exec" (alias ssh) to open a remote console#1027
kke wants to merge 1 commit intomainfrom
k0sctl-ssh

kke commented Feb 12, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI Feb 12, 2026

Uh oh!

Copilot AI Feb 12, 2026

Uh oh!

Copilot AI Feb 12, 2026

Uh oh!

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI Feb 12, 2026

Uh oh!

Copilot AI Feb 12, 2026

Uh oh!

Copilot AI Feb 12, 2026

Uh oh!

Copilot AI Feb 12, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

1 participant

	Usage: "Run command on hosts in parallel",
	Usage: "Run command on hosts in parallel (only applies when a command is provided, not in interactive mode)",

Conversation

kke commented Feb 12, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Copilot AI Feb 12, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Feb 12, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Feb 12, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Copilot AI Feb 12, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Feb 12, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Feb 12, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Feb 12, 2026

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

1 participant