package server import ( "bufio" "bytes" "encoding/json" "errors" "fmt" "github.com/dotcloud/docker" "github.com/dotcloud/docker/future" "github.com/dotcloud/docker/image" "github.com/dotcloud/docker/rcli" "io" "net/http" "net/url" "os" "path" "strconv" "strings" "sync" "text/tabwriter" "time" ) const VERSION = "0.0.1" func (srv *Server) ListenAndServe() error { go rcli.ListenAndServeHTTP("127.0.0.1:8080", srv) // FIXME: we want to use unix sockets here, but net.UnixConn doesn't expose // CloseWrite(), which we need to cleanly signal that stdin is closed without // closing the connection. // See http://code.google.com/p/go/issues/detail?id=3345 return rcli.ListenAndServe("tcp", "127.0.0.1:4242", srv) } func (srv *Server) Name() string { return "docker" } func (srv *Server) Help() string { help := "Usage: docker COMMAND [arg...]\n\nA self-sufficient runtime for linux containers.\n\nCommands:\n" for _, cmd := range [][]interface{}{ {"run", "Run a command in a container"}, {"ps", "Display a list of containers"}, {"pull", "Download a tarball and create a container from it"}, {"put", "Upload a tarball and create a container from it"}, {"rm", "Remove containers"}, {"kill", "Kill a running container"}, {"wait", "Wait for the state of a container to change"}, {"stop", "Stop a running container"}, {"start", "Start a stopped container"}, {"restart", "Restart a running container"}, {"logs", "Fetch the logs of a container"}, {"diff", "Inspect changes on a container's filesystem"}, {"commit", "Save the state of a container"}, {"attach", "Attach to the standard inputs and outputs of a running container"}, {"wait", "Block until a container exits, then print its exit code"}, {"info", "Display system-wide information"}, {"tar", "Stream the contents of a container as a tar archive"}, {"web", "Generate a web UI"}, {"images", "List images"}, } { help += fmt.Sprintf(" %-10.10s%s\n", cmd...) } return help } // 'docker wait': block until a container stops func (srv *Server) CmdWait(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "wait", "[OPTIONS] NAME", "Block until a container stops, then print its exit code.") if err := cmd.Parse(args); err != nil { cmd.Usage() return nil } if cmd.NArg() < 1 { cmd.Usage() return nil } for _, name := range cmd.Args() { if container := srv.containers.Get(name); container != nil { fmt.Fprintln(stdout, container.Wait()) } else { return errors.New("No such container: " + name) } } return nil } // 'docker info': display system-wide information. func (srv *Server) CmdInfo(stdin io.ReadCloser, stdout io.Writer, args ...string) error { fmt.Fprintf(stdout, "containers: %d\nversion: %s\nimages: %d\n", len(srv.containers.List()), VERSION, len(srv.images.ById)) return nil } func (srv *Server) CmdStop(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "stop", "[OPTIONS] NAME", "Stop a running container") if err := cmd.Parse(args); err != nil { cmd.Usage() return nil } if cmd.NArg() < 1 { cmd.Usage() return nil } for _, name := range cmd.Args() { if container := srv.containers.Get(name); container != nil { if err := container.Stop(); err != nil { return err } fmt.Fprintln(stdout, container.Id) } else { return errors.New("No such container: " + name) } } return nil } func (srv *Server) CmdRestart(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "restart", "[OPTIONS] NAME", "Restart a running container") if err := cmd.Parse(args); err != nil { cmd.Usage() return nil } if cmd.NArg() < 1 { cmd.Usage() return nil } for _, name := range cmd.Args() { if container := srv.containers.Get(name); container != nil { if err := container.Restart(); err != nil { return err } fmt.Fprintln(stdout, container.Id) } else { return errors.New("No such container: " + name) } } return nil } func (srv *Server) CmdStart(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "start", "[OPTIONS] NAME", "Start a stopped container") if err := cmd.Parse(args); err != nil { cmd.Usage() return nil } if cmd.NArg() < 1 { cmd.Usage() return nil } for _, name := range cmd.Args() { if container := srv.containers.Get(name); container != nil { if err := container.Start(); err != nil { return err } fmt.Fprintln(stdout, container.Id) } else { return errors.New("No such container: " + name) } } return nil } func (srv *Server) CmdUmount(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "umount", "[OPTIONS] NAME", "umount a container's filesystem (debug only)") if err := cmd.Parse(args); err != nil { cmd.Usage() return nil } if cmd.NArg() < 1 { cmd.Usage() return nil } for _, name := range cmd.Args() { if container := srv.containers.Get(name); container != nil { if err := container.Filesystem.Umount(); err != nil { return err } fmt.Fprintln(stdout, container.Id) } else { return errors.New("No such container: " + name) } } return nil } func (srv *Server) CmdMount(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "umount", "[OPTIONS] NAME", "mount a container's filesystem (debug only)") if err := cmd.Parse(args); err != nil { cmd.Usage() return nil } if cmd.NArg() < 1 { cmd.Usage() return nil } for _, name := range cmd.Args() { if container := srv.containers.Get(name); container != nil { if err := container.Filesystem.Mount(); err != nil { return err } fmt.Fprintln(stdout, container.Id) } else { return errors.New("No such container: " + name) } } return nil } func (srv *Server) CmdCat(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "cat", "[OPTIONS] CONTAINER PATH", "write the contents of a container's file to standard output") if err := cmd.Parse(args); err != nil { cmd.Usage() return nil } if cmd.NArg() < 2 { cmd.Usage() return nil } name, path := cmd.Arg(0), cmd.Arg(1) if container := srv.containers.Get(name); container != nil { if f, err := container.Filesystem.OpenFile(path, os.O_RDONLY, 0); err != nil { return err } else if _, err := io.Copy(stdout, f); err != nil { return err } return nil } return errors.New("No such container: " + name) } func (srv *Server) CmdWrite(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "write", "[OPTIONS] CONTAINER PATH", "write the contents of standard input to a container's file") if err := cmd.Parse(args); err != nil { cmd.Usage() return nil } if cmd.NArg() < 2 { cmd.Usage() return nil } name, path := cmd.Arg(0), cmd.Arg(1) if container := srv.containers.Get(name); container != nil { if f, err := container.Filesystem.OpenFile(path, os.O_WRONLY|os.O_CREATE, 0600); err != nil { return err } else if _, err := io.Copy(f, stdin); err != nil { return err } return nil } return errors.New("No such container: " + name) } func (srv *Server) CmdLs(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "ls", "[OPTIONS] CONTAINER PATH", "List the contents of a container's directory") if err := cmd.Parse(args); err != nil { cmd.Usage() return nil } if cmd.NArg() < 2 { cmd.Usage() return nil } name, path := cmd.Arg(0), cmd.Arg(1) if container := srv.containers.Get(name); container != nil { if files, err := container.Filesystem.ReadDir(path); err != nil { return err } else { for _, f := range files { fmt.Fprintln(stdout, f.Name()) } } return nil } return errors.New("No such container: " + name) } func (srv *Server) CmdInspect(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "inspect", "[OPTIONS] CONTAINER", "Return low-level information on a container") if err := cmd.Parse(args); err != nil { cmd.Usage() return nil } if cmd.NArg() < 1 { cmd.Usage() return nil } name := cmd.Arg(0) var obj interface{} if container := srv.containers.Get(name); container != nil { obj = container } else if image := srv.images.Find(name); image != nil { obj = image } else { return errors.New("No such container or image: " + name) } data, err := json.Marshal(obj) if err != nil { return err } indented := new(bytes.Buffer) if err = json.Indent(indented, data, "", " "); err != nil { return err } if _, err := io.Copy(stdout, indented); err != nil { return err } return nil } // 'docker rmi NAME' removes all images with the name NAME func (srv *Server) CmdRmi(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "rmimage", "[OPTIONS] IMAGE", "Remove an image") if err := cmd.Parse(args); err != nil { cmd.Usage() return nil } if cmd.NArg() < 1 { cmd.Usage() return nil } for _, name := range cmd.Args() { image := srv.images.Find(name) if image == nil { return errors.New("No such image: " + name) } if err := srv.images.Delete(name); err != nil { return err } } return nil } func (srv *Server) CmdRm(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "rm", "[OPTIONS] CONTAINER", "Remove a container") if err := cmd.Parse(args); err != nil { return nil } for _, name := range cmd.Args() { container := srv.containers.Get(name) if container == nil { return errors.New("No such container: " + name) } if err := srv.containers.Destroy(container); err != nil { fmt.Fprintln(stdout, "Error destroying container "+name+": "+err.Error()) } } return nil } // 'docker kill NAME' kills a running container func (srv *Server) CmdKill(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "kill", "[OPTIONS] CONTAINER [CONTAINER...]", "Kill a running container") if err := cmd.Parse(args); err != nil { return nil } for _, name := range cmd.Args() { container := srv.containers.Get(name) if container == nil { return errors.New("No such container: " + name) } if err := container.Kill(); err != nil { fmt.Fprintln(stdout, "Error killing container "+name+": "+err.Error()) } } return nil } func (srv *Server) CmdPull(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "pull", "[OPTIONS] NAME", "Download a new image from a remote location") if err := cmd.Parse(args); err != nil { return nil } name := cmd.Arg(0) if name == "" { return errors.New("Not enough arguments") } u, err := url.Parse(name) if err != nil { return err } if u.Scheme == "" { u.Scheme = "http" } // FIXME: hardcode a mirror URL that does not depend on a single provider. if u.Host == "" { u.Host = "s3.amazonaws.com" u.Path = path.Join("/docker.io/images", u.Path) } fmt.Fprintf(stdout, "Downloading from %s\n", u.String()) // Download with curl (pretty progress bar) // If curl is not available, fallback to http.Get() archive, err := future.Curl(u.String(), stdout) if err != nil { if resp, err := http.Get(u.String()); err != nil { return err } else { archive = resp.Body } } fmt.Fprintf(stdout, "Unpacking to %s\n", name) img, err := srv.images.Import(name, archive, nil) if err != nil { return err } fmt.Fprintln(stdout, img.Id) return nil } func (srv *Server) CmdPut(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "put", "[OPTIONS] NAME", "Import a new image from a local archive.") if err := cmd.Parse(args); err != nil { return nil } name := cmd.Arg(0) if name == "" { return errors.New("Not enough arguments") } img, err := srv.images.Import(name, stdin, nil) if err != nil { return err } fmt.Fprintln(stdout, img.Id) return nil } func (srv *Server) CmdImages(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "images", "[OPTIONS] [NAME]", "List images") limit := cmd.Int("l", 0, "Only show the N most recent versions of each image") quiet := cmd.Bool("q", false, "only show numeric IDs") cmd.Parse(args) if cmd.NArg() > 1 { cmd.Usage() return nil } var nameFilter string if cmd.NArg() == 1 { nameFilter = cmd.Arg(0) } w := tabwriter.NewWriter(stdout, 20, 1, 3, ' ', 0) if !*quiet { fmt.Fprintf(w, "NAME\tID\tCREATED\tPARENT\n") } for _, name := range srv.images.Names() { if nameFilter != "" && nameFilter != name { continue } for idx, img := range *srv.images.ByName[name] { if *limit > 0 && idx >= *limit { break } if !*quiet { id := img.Id if !img.IdIsFinal() { id += "..." } for idx, field := range []string{ /* NAME */ name, /* ID */ id, /* CREATED */ future.HumanDuration(time.Now().Sub(img.Created)) + " ago", /* PARENT */ img.Parent, } { if idx == 0 { w.Write([]byte(field)) } else { w.Write([]byte("\t" + field)) } } w.Write([]byte{'\n'}) } else { stdout.Write([]byte(img.Id + "\n")) } } } if !*quiet { w.Flush() } return nil } func (srv *Server) CmdPs(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "ps", "[OPTIONS]", "List containers") quiet := cmd.Bool("q", false, "Only display numeric IDs") fl_all := cmd.Bool("a", false, "Show all containers. Only running containers are shown by default.") fl_full := cmd.Bool("notrunc", false, "Don't truncate output") if err := cmd.Parse(args); err != nil { return nil } w := tabwriter.NewWriter(stdout, 12, 1, 3, ' ', 0) if !*quiet { fmt.Fprintf(w, "ID\tIMAGE\tCOMMAND\tCREATED\tSTATUS\tCOMMENT\n") } for _, container := range srv.containers.List() { comment := container.GetUserData("comment") if !container.State.Running && !*fl_all { continue } if !*quiet { command := fmt.Sprintf("%s %s", container.Path, strings.Join(container.Args, " ")) if !*fl_full { command = docker.Trunc(command, 20) } for idx, field := range []string{ /* ID */ container.Id, /* IMAGE */ container.GetUserData("image"), /* COMMAND */ command, /* CREATED */ future.HumanDuration(time.Now().Sub(container.Created)) + " ago", /* STATUS */ container.State.String(), /* COMMENT */ comment, } { if idx == 0 { w.Write([]byte(field)) } else { w.Write([]byte("\t" + field)) } } w.Write([]byte{'\n'}) } else { stdout.Write([]byte(container.Id + "\n")) } } if !*quiet { w.Flush() } return nil } func (srv *Server) CmdLayers(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "layers", "[OPTIONS]", "List filesystem layers (debug only)") if err := cmd.Parse(args); err != nil { return nil } for _, layer := range srv.images.Layers.List() { fmt.Fprintln(stdout, layer) } return nil } func (srv *Server) CmdCp(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "cp", "[OPTIONS] IMAGE NAME", "Create a copy of IMAGE and call it NAME") if err := cmd.Parse(args); err != nil { return nil } if newImage, err := srv.images.Copy(cmd.Arg(0), cmd.Arg(1)); err != nil { return err } else { fmt.Fprintln(stdout, newImage.Id) } return nil } func (srv *Server) CmdCommit(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "commit", "[OPTIONS] CONTAINER [DEST]", "Create a new image from a container's changes") if err := cmd.Parse(args); err != nil { return nil } containerName, imgName := cmd.Arg(0), cmd.Arg(1) if containerName == "" || imgName == "" { cmd.Usage() return nil } if container := srv.containers.Get(containerName); container != nil { // FIXME: freeze the container before copying it to avoid data corruption? rwTar, err := image.Tar(container.Filesystem.RWPath, image.Uncompressed) if err != nil { return err } // Create a new image from the container's base layers + a new layer from container changes parentImg := srv.images.Find(container.GetUserData("image")) img, err := srv.images.Import(imgName, rwTar, parentImg) if err != nil { return err } fmt.Fprintln(stdout, img.Id) return nil } return errors.New("No such container: " + containerName) } func (srv *Server) CmdTar(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "tar", "CONTAINER", "Stream the contents of a container as a tar archive") fl_sparse := cmd.Bool("s", false, "Generate a sparse tar stream (top layer + reference to bottom layers)") if err := cmd.Parse(args); err != nil { return nil } if *fl_sparse { return errors.New("Sparse mode not yet implemented") // FIXME } name := cmd.Arg(0) if container := srv.containers.Get(name); container != nil { data, err := container.Filesystem.Tar() if err != nil { return err } // Stream the entire contents of the container (basically a volatile snapshot) if _, err := io.Copy(stdout, data); err != nil { return err } return nil } return errors.New("No such container: " + name) } func (srv *Server) CmdDiff(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "diff", "CONTAINER [OPTIONS]", "Inspect changes on a container's filesystem") if err := cmd.Parse(args); err != nil { return nil } if cmd.NArg() < 1 { return errors.New("Not enough arguments") } if container := srv.containers.Get(cmd.Arg(0)); container == nil { return errors.New("No such container") } else { changes, err := container.Filesystem.Changes() if err != nil { return err } for _, change := range changes { fmt.Fprintln(stdout, change.String()) } } return nil } func (srv *Server) CmdReset(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "reset", "CONTAINER [OPTIONS]", "Reset changes to a container's filesystem") if err := cmd.Parse(args); err != nil { return nil } if cmd.NArg() < 1 { return errors.New("Not enough arguments") } for _, name := range cmd.Args() { if container := srv.containers.Get(name); container != nil { if err := container.Filesystem.Reset(); err != nil { return errors.New("Reset " + container.Id + ": " + err.Error()) } } } return nil } func (srv *Server) CmdLogs(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "logs", "[OPTIONS] CONTAINER", "Fetch the logs of a container") if err := cmd.Parse(args); err != nil { return nil } if cmd.NArg() != 1 { cmd.Usage() return nil } name := cmd.Arg(0) if container := srv.containers.Get(name); container != nil { if _, err := io.Copy(stdout, container.StdoutLog()); err != nil { return err } if _, err := io.Copy(stdout, container.StderrLog()); err != nil { return err } return nil } return errors.New("No such container: " + cmd.Arg(0)) } func (srv *Server) CreateContainer(img *image.Image, ports []int, user string, tty bool, openStdin bool, comment string, cmd string, args ...string) (*docker.Container, error) { id := future.RandomId()[:8] container, err := srv.containers.Create(id, cmd, args, img.Layers, &docker.Config{Hostname: id, Ports: ports, User: user, Tty: tty, OpenStdin: openStdin}) if err != nil { return nil, err } if err := container.SetUserData("image", img.Id); err != nil { srv.containers.Destroy(container) return nil, errors.New("Error setting container userdata: " + err.Error()) } if err := container.SetUserData("comment", comment); err != nil { srv.containers.Destroy(container) return nil, errors.New("Error setting container userdata: " + err.Error()) } return container, nil } func (srv *Server) CmdAttach(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "attach", "[OPTIONS]", "Attach to a running container") fl_i := cmd.Bool("i", false, "Attach to stdin") fl_o := cmd.Bool("o", true, "Attach to stdout") fl_e := cmd.Bool("e", true, "Attach to stderr") if err := cmd.Parse(args); err != nil { return nil } if cmd.NArg() != 1 { cmd.Usage() return nil } name := cmd.Arg(0) container := srv.containers.Get(name) if container == nil { return errors.New("No such container: " + name) } var wg sync.WaitGroup if *fl_i { c_stdin, err := container.StdinPipe() if err != nil { return err } wg.Add(1) go func() { io.Copy(c_stdin, stdin); wg.Add(-1) }() } if *fl_o { c_stdout, err := container.StdoutPipe() if err != nil { return err } wg.Add(1) go func() { io.Copy(stdout, c_stdout); wg.Add(-1) }() } if *fl_e { c_stderr, err := container.StderrPipe() if err != nil { return err } wg.Add(1) go func() { io.Copy(stdout, c_stderr); wg.Add(-1) }() } wg.Wait() return nil } // Ports type - Used to parse multiple -p flags type ports []int func (p *ports) String() string { return fmt.Sprint(*p) } func (p *ports) Set(value string) error { port, err := strconv.Atoi(value) if err != nil { return fmt.Errorf("Invalid port: %v", value) } *p = append(*p, port) return nil } func (srv *Server) CmdRun(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "run", "[OPTIONS] IMAGE COMMAND [ARG...]", "Run a command in a new container") fl_user := cmd.String("u", "", "Username or UID") fl_attach := cmd.Bool("a", false, "Attach stdin and stdout") fl_stdin := cmd.Bool("i", false, "Keep stdin open even if not attached") fl_tty := cmd.Bool("t", false, "Allocate a pseudo-tty") fl_comment := cmd.String("c", "", "Comment") var fl_ports ports cmd.Var(&fl_ports, "p", "Map a network port to the container") if err := cmd.Parse(args); err != nil { return nil } name := cmd.Arg(0) var cmdline []string if len(cmd.Args()) >= 2 { cmdline = cmd.Args()[1:] } // Choose a default image if needed if name == "" { name = "base" } // Choose a default command if needed if len(cmdline) == 0 { *fl_stdin = true *fl_tty = true *fl_attach = true cmdline = []string{"/bin/bash", "-i"} } // Find the image img := srv.images.Find(name) if img == nil { return errors.New("No such image: " + name) } // Create new container container, err := srv.CreateContainer(img, fl_ports, *fl_user, *fl_tty, *fl_stdin, *fl_comment, cmdline[0], cmdline[1:]...) if err != nil { return errors.New("Error creating container: " + err.Error()) } if *fl_stdin { cmd_stdin, err := container.StdinPipe() if err != nil { return err } if *fl_attach { future.Go(func() error { _, err := io.Copy(cmd_stdin, stdin) cmd_stdin.Close() return err }) } } // Run the container if *fl_attach { cmd_stderr, err := container.StderrPipe() if err != nil { return err } cmd_stdout, err := container.StdoutPipe() if err != nil { return err } if err := container.Start(); err != nil { return err } sending_stdout := future.Go(func() error { _, err := io.Copy(stdout, cmd_stdout) return err }) sending_stderr := future.Go(func() error { _, err := io.Copy(stdout, cmd_stderr) return err }) err_sending_stdout := <-sending_stdout err_sending_stderr := <-sending_stderr if err_sending_stdout != nil { return err_sending_stdout } if err_sending_stderr != nil { return err_sending_stderr } container.Wait() } else { if err := container.Start(); err != nil { return err } fmt.Fprintln(stdout, container.Id) } return nil } func New() (*Server, error) { future.Seed() images, err := image.New("/var/lib/docker/images") if err != nil { return nil, err } containers, err := docker.New() if err != nil { return nil, err } srv := &Server{ images: images, containers: containers, } return srv, nil } func (srv *Server) CmdMirror(stdin io.ReadCloser, stdout io.Writer, args ...string) error { _, err := io.Copy(stdout, stdin) return err } func (srv *Server) CmdDebug(stdin io.ReadCloser, stdout io.Writer, args ...string) error { for { if line, err := bufio.NewReader(stdin).ReadString('\n'); err == nil { fmt.Printf("--- %s", line) } else if err == io.EOF { if len(line) > 0 { fmt.Printf("--- %s\n", line) } break } else { return err } } return nil } func (srv *Server) CmdWeb(stdin io.ReadCloser, stdout io.Writer, args ...string) error { cmd := rcli.Subcmd(stdout, "web", "[OPTIONS]", "A web UI for docker") showurl := cmd.Bool("u", false, "Return the URL of the web UI") if err := cmd.Parse(args); err != nil { return nil } if *showurl { fmt.Fprintln(stdout, "http://localhost:4242/web") } else { if file, err := os.Open("dockerweb.html"); err != nil { return err } else if _, err := io.Copy(stdout, file); err != nil { return err } } return nil } type Server struct { containers *docker.Docker images *image.Store }