implement ignite exec

cmd/ignite/cmd/exec.go

@@ -0,0 +1,13 @@
+package cmd
+
+import (
+	"io"
+
+	"github.com/spf13/cobra"
+	"github.com/weaveworks/ignite/cmd/ignite/cmd/vmcmd"
+)
+
+// NewCmdExec is an alias for vmcmd.NewCmdExec
+func NewCmdExec(out io.Writer, err io.Writer, in io.Reader) *cobra.Command {
+	return vmcmd.NewCmdExec(out, err, in)
+}

cmd/ignite/cmd/root.go

@@ -93,6 +93,7 @@ func NewIgniteCommand(in io.Reader, out, err io.Writer) *cobra.Command {
 	root.AddCommand(NewCmdRmk(os.Stdout))
 	root.AddCommand(NewCmdRun(os.Stdout))
 	root.AddCommand(NewCmdSSH(os.Stdout))
+	root.AddCommand(NewCmdExec(os.Stdout, os.Stderr, os.Stdin))
 	root.AddCommand(NewCmdStart(os.Stdout))
 	root.AddCommand(NewCmdStop(os.Stdout))
 	root.AddCommand(NewCmdVersion(os.Stdout))

cmd/ignite/cmd/vmcmd/exec.go

@@ -0,0 +1,46 @@
+package vmcmd
+
+import (
+	"io"
+
+	"github.com/lithammer/dedent"
+	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
+	"github.com/weaveworks/ignite/cmd/ignite/run"
+	"github.com/weaveworks/ignite/pkg/errutils"
+)
+
+// NewCmdExec exec's into a running VM
+func NewCmdExec(out io.Writer, err io.Writer, in io.Reader) *cobra.Command {
+	ef := &run.ExecFlags{}
+
+	cmd := &cobra.Command{
+		Use:   "exec <vm> <command...>",
+		Short: "execute a command in a running VM",
+		Long: dedent.Dedent(`
+			Execute a command in a running VM using SSH and the private key created for it during generation.
+			If no private key was created or wanting to use a different identity file,
+			use the identity file flag (-i, --identity) to override the used identity file.
+			The given VM is matched by prefix based on its ID and name.
+		`),
+		Args: cobra.MinimumNArgs(2),
+		Run: func(cmd *cobra.Command, args []string) {
+			errutils.Check(func() error {
+				eo, err := ef.NewExecOptions(args[0], args[1:]...)
+				if err != nil {
+					return err
+				}
+
+				return run.Exec(eo)
+			}())
+		},
+	}
+
+	addExecFlags(cmd.Flags(), ef)
+	return cmd
+}
+
+func addExecFlags(fs *pflag.FlagSet, ef *run.ExecFlags) {
+	fs.StringVarP(&ef.IdentityFile, "identity", "i", "", "Override the vm's default identity file")
+	fs.Uint32VarP(&ef.Timeout, "timeout", "t", 10, "Timeout waiting for connection in seconds")
+}

cmd/ignite/run/exec.go

@@ -0,0 +1,155 @@
+package run
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net"
+	"os"
+	"path"
+	"time"
+
+	api "github.com/weaveworks/ignite/pkg/apis/ignite"
+	"github.com/weaveworks/ignite/pkg/constants"
+	"github.com/weaveworks/ignite/pkg/util"
+	"golang.org/x/crypto/ssh"
+	shellescape "gopkg.in/alessio/shellescape.v1"
+)
+
+type ExecFlags struct {
+	Timeout      uint32
+	IdentityFile string
+}
+
+type execOptions struct {
+	*ExecFlags
+	vm      *api.VM
+	command []string
+}
+
+func (ef *ExecFlags) NewExecOptions(vmMatch string, command ...string) (eo *execOptions, err error) {
+	eo = &execOptions{
+		ExecFlags: ef,
+		command:   command,
+	}
+
+	eo.vm, err = getVMForMatch(vmMatch)
+	return
+}
+
+func Exec(eo *execOptions) error {
+	// Check if the VM is running
+	if !eo.vm.Running() {
+		return fmt.Errorf("VM %q is not running", eo.vm.GetUID())
+	}
+
+	// Get the IP address
+	ipAddrs := eo.vm.Status.IPAddresses
+	if len(ipAddrs) == 0 {
+		return fmt.Errorf("VM %q has no usable IP addresses", eo.vm.GetUID())
+	}
+
+	// If an external identity file is specified, use it instead of the internal one
+	privKeyFile := eo.IdentityFile
+	if len(privKeyFile) == 0 {
+		privKeyFile = path.Join(eo.vm.ObjectPath(), fmt.Sprintf(constants.VM_SSH_KEY_TEMPLATE, eo.vm.GetUID()))
+		if !util.FileExists(privKeyFile) {
+			return fmt.Errorf("no private key found for VM %q", eo.vm.GetUID())
+		}
+	}
+
+	signer, err := newSignerForKey(privKeyFile)
+	if err != nil {
+		return fmt.Errorf("unable to create signer for private key: %v", err)
+	}
+
+	// Create an SSH client, and connect, we will use this to exec
+	config := newSSHConfig(signer, eo.Timeout)
+	client, err := ssh.Dial("tcp", net.JoinHostPort(ipAddrs[0].String(), "22"), config)
+	if err != nil {
+		return fmt.Errorf("failed to dial: %v", err)
+	}
+
+	// Run the command, DO NOT wrap this error as the caller can check for the command exit
+	// code in the ssh.ExitError type
+	return runSSHCommand(client, eo.command)
+}
+
+func newSignerForKey(keyPath string) (ssh.Signer, error) {
+	key, err := ioutil.ReadFile(keyPath)
+	if err != nil {
+		return nil, fmt.Errorf("unable to read private key: %v", err)
+	}
+
+	// Create the Signer for this private key.
+	return ssh.ParsePrivateKey(key)
+}
+
+func newSSHConfig(publicKey ssh.Signer, timeout uint32) *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User: "root",
+		Auth: []ssh.AuthMethod{
+			ssh.PublicKeys(publicKey),
+		},
+		HostKeyCallback: ssh.InsecureIgnoreHostKey(), // TODO: use ssh.FixedPublicKey instead
+		Timeout:         time.Second * time.Duration(timeout),
+	}
+}
+
+func runSSHCommand(client *ssh.Client, command []string) error {
+	// create a session for the command
+	session, err := client.NewSession()
+	if err != nil {
+		return fmt.Errorf("failed to create session: %v", err)
+	}
+	defer session.Close()
+
+	// get a pty
+	// TODO: should these be based on the host terminal?
+	// TODO: should we request something other than xterm?
+	// TODO: we should probably configure the terminal modes
+	modes := ssh.TerminalModes{}
+	if err := session.RequestPty("xterm", 80, 40, modes); err != nil {
+		return fmt.Errorf("request for pseudo terminal failed: %v", err)
+	}
+
+	// connect input / output
+	// TODO: these should come from the cobra command instead of hardcoding os.Stderr etc.
+	stderr, err := session.StderrPipe()
+	if err != nil {
+		return fmt.Errorf("failed to connect stderr: %v", err)
+	}
+	go io.Copy(os.Stderr, stderr)
+	stdout, err := session.StdoutPipe()
+	if err != nil {
+		return fmt.Errorf("failed to connect stdout: %v", err)
+	}
+	go io.Copy(os.Stdout, stdout)
+	stdin, err := session.StdinPipe()
+	if err != nil {
+		return fmt.Errorf("failed to connect stdin: %v", err)
+	}
+	go io.Copy(stdin, os.Stdin)
+
+	/*
+		Do not wrap this error so the caller can check for the exit code
+		If the remote server does not send an exit status, an error of type *ExitMissingError is returned.
+		If the command completes unsuccessfully or is interrupted by a signal, the error is of type *ExitError.
+		Other error types may be returned for I/O problems.
+	*/
+	return session.Run(joinShellCommand(command))
+}
+
+// joinShellCommand joins command parts into a single string safe for passing to sh -c (or SSH)
+func joinShellCommand(command []string) string {
+	joined := command[0]
+	if len(command) == 1 {
+		return joined
+	}
+	for _, arg := range command[1:] {
+		// NOTE: we need to escape / quote to ensure that
+		// each component of command... is read as a single shell word
+		joined += " " + shellescape.Quote(arg)
+	}
+	return joined
+}

cmd/ignite/run/ssh.go

@@ -8,8 +8,6 @@ import (
 	api "github.com/weaveworks/ignite/pkg/apis/ignite"
 	"github.com/weaveworks/ignite/pkg/constants"
 	"github.com/weaveworks/ignite/pkg/util"
-
-	_ "golang.org/x/crypto/ssh"
 )
 
 type SSHFlags struct {

docs/cli/ignite.md

@@ -43,6 +43,7 @@ Example usage:
 * [ignite attach](ignite_attach.md)	 - Attach to a running VM
 * [ignite completion](ignite_completion.md)	 - Output bash completion for ignite to stdout
 * [ignite create](ignite_create.md)	 - Create a new VM without starting it
+* [ignite exec](ignite_exec.md)	 - execute a command in a running VM
 * [ignite gitops](ignite_gitops.md)	 - Run the GitOps feature of Ignite
 * [ignite image](ignite_image.md)	 - Manage base images for VMs
 * [ignite inspect](ignite_inspect.md)	 - Inspect an Ignite Object

docs/cli/ignite_exec.md

@@ -0,0 +1,36 @@
+## ignite exec
+
+execute a command in a running VM
+
+### Synopsis
+
+
+Execute a command in a running VM using SSH and the private key created for it during generation.
+If no private key was created or wanting to use a different identity file,
+use the identity file flag (-i, --identity) to override the used identity file.
+The given VM is matched by prefix based on its ID and name.
+
+
+```
+ignite exec <vm> <command...> [flags]
+```
+
+### Options
+
+```
+  -h, --help              help for exec
+  -i, --identity string   Override the vm's default identity file
+  -t, --timeout uint32    Timeout waiting for connection in seconds (default 10)
+```
+
+### Options inherited from parent commands
+
+```
+      --log-level loglevel   Specify the loglevel for the program (default info)
+  -q, --quiet                The quiet mode allows for machine-parsable output, by printing only IDs
+```
+
+### SEE ALSO
+
+* [ignite](ignite.md)	 - ignite: easily run Firecracker VMs
+

pkg/errutils/errors.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"os"
 	"strings"
+
+	"golang.org/x/crypto/ssh"
 )
 
 const (
@@ -34,6 +36,9 @@ func Check(err error) {
 	switch err.(type) {
 	case nil:
 		return
+	case *ssh.ExitError:
+		exitError := err.(*ssh.ExitError)
+		fatal(err.Error(), exitError.ExitStatus())
 	default:
 		fatal(err.Error(), DefaultErrorExitCode)
 	}