add --mount option to ctr

Signed-off-by: Evan Hazlett <ejhazlett@gmail.com>

cmd/ctr/run.go

@@ -54,6 +54,10 @@ var runCommand = cli.Command{
 			Name:  "net-host",
 			Usage: "enable host networking for the container",
 		},
+		cli.StringSliceFlag{
+			Name:  "mount",
+			Usage: "specify additional container mount (ex: type=bind,src=/tmp,dest=/host,options=rbind:ro)",
+		},
 		cli.BoolFlag{
 			Name:  "keep",
 			Usage: "keep container after running",

cmd/ctr/run_unix.go

@@ -222,6 +222,14 @@ func spec(id string, config *ocispec.ImageConfig, context *cli.Context, rootfs s
 			Type: "network",
 		})
 	}
+	for _, mount := range context.StringSlice("mount") {
+		m, err := parseMountFlag(mount)
+		if err != nil {
+			return nil, err
+		}
+
+		s.Mounts = append(s.Mounts, m)
+	}
 	return s, nil
 }
 

cmd/ctr/utils.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	gocontext "context"
+	"encoding/csv"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -26,6 +27,7 @@ import (
 	imagesservice "github.com/containerd/containerd/services/images"
 	snapshotservice "github.com/containerd/containerd/services/snapshot"
 	"github.com/containerd/containerd/snapshot"
+	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/urfave/cli"
 	"google.golang.org/grpc"
 )
@@ -152,3 +154,38 @@ func stopCatch(sigc chan os.Signal) {
 	signal.Stop(sigc)
 	close(sigc)
 }
+
+// parseMountFlag parses a mount string in the form "type=foo,source=/path,destination=/target,options=rbind:rw"
+func parseMountFlag(m string) (specs.Mount, error) {
+	mount := specs.Mount{}
+	r := csv.NewReader(strings.NewReader(m))
+
+	fields, err := r.Read()
+	if err != nil {
+		return mount, err
+	}
+
+	for _, field := range fields {
+		v := strings.Split(field, "=")
+		if len(v) != 2 {
+			return mount, fmt.Errorf("invalid mount specification: expected key=val")
+		}
+
+		key := v[0]
+		val := v[1]
+		switch key {
+		case "type":
+			mount.Type = val
+		case "source", "src":
+			mount.Source = val
+		case "destination", "dst":
+			mount.Destination = val
+		case "options":
+			mount.Options = strings.Split(val, ":")
+		default:
+			return mount, fmt.Errorf("mount option %q not supported", key)
+		}
+	}
+
+	return mount, nil
+}