Create draft of FreeBSD runtime spec

Ref. opencontainers#364

oci/config/convert/default.go

@@ -24,9 +24,9 @@ import (
 	"github.com/pkg/errors"
 )
 
-// Example returns an example spec file, used as a "good sane default".
+// Example returns an example spec file for Linux images, used as a "good sane default".
 // XXX: Really we should just use runc's directly.
-func Example() rspec.Spec {
+func Example_Linux() rspec.Spec {
 	return rspec.Spec{
 		Version: rspec.Version,
 		Root: &rspec.Root{
@@ -172,6 +172,53 @@ func Example() rspec.Spec {
 	}
 }
 
+// Example returns an example spec file for FreeBSD images, used as a "good sane default".
+// XXX: Really we should just use runc's directly.
+func Example_FreeBSD() rspec.Spec {
+	return rspec.Spec{
+		Version: rspec.Version,
+		Root: &rspec.Root{
+			Path:     "rootfs",
+			Readonly: false,
+		},
+		Process: &rspec.Process{
+			Terminal: true,
+			User:     rspec.User{},
+			Args: []string{
+				"sh",
+			},
+			Env: []string{
+				"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
+				"TERM=xterm",
+			},
+			Cwd:             "/",
+			NoNewPrivileges: true,
+			Rlimits: []rspec.POSIXRlimit{
+				{
+					Type: "RLIMIT_NOFILE",
+					Hard: uint64(1024),
+					Soft: uint64(1024),
+				},
+			},
+		},
+		Hostname: "umoci-default",
+		Mounts: []rspec.Mount{
+			{
+				Destination: "/dev",
+				Type:        "devfs",
+				Source:      "devfs",
+				Options:     []string{},
+			},
+			{
+				Destination: "/dev/fd",
+				Type:        "fdescfs",
+				Source:      "fdescfs",
+				Options:     []string{},
+			},
+		},
+	}
+}
+
 // ToRootless converts a specification to a version that works with rootless
 // containers. This is done by removing options and other settings that clash
 // with unprivileged user namespaces.

oci/config/convert/runtime.go

@@ -46,7 +46,13 @@ const (
 // configuration specified by the OCI runtime-tools. It is equivalent to
 // MutateRuntimeSpec("runtime-tools/generate".New(), image).Spec().
 func ToRuntimeSpec(rootfs string, image ispec.Image) (rspec.Spec, error) {
-	spec := Example()
+	var spec rspec.Spec
+	switch image.OS {
+		case "linux": spec = Example_Linux()
+		case "freebsd": spec = Example_FreeBSD()
+		default: return rspec.Spec{}, errors.Errorf("unsupported OS: %s", image.OS)
+	}
+
 	if err := MutateRuntimeSpec(&spec, rootfs, image); err != nil {
 		return rspec.Spec{}, err
 	}
@@ -110,10 +116,6 @@ func MutateRuntimeSpec(spec *rspec.Spec, rootfs string, image ispec.Image) error
 		return errors.Wrap(err, "creating image generator")
 	}
 
-	if ig.OS() != "linux" {
-		return errors.Errorf("unsupported OS: %s", image.OS)
-	}
-
 	allocateNilStruct(spec)
 
 	// FIXME: We need to figure out if we're modifying an incompatible runtime spec.