Revert "rootfs: remove unused functions"

This reverts commit 4e2337794c.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

rootfs/init.go

@@ -0,0 +1,99 @@
+package rootfs
+
+import (
+	"context"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	"github.com/containerd/containerd/log"
+	"github.com/containerd/containerd/mount"
+	"github.com/containerd/containerd/snapshot"
+	digest "github.com/opencontainers/go-digest"
+	"github.com/pkg/errors"
+)
+
+var (
+	initializers = map[string]initializerFunc{}
+)
+
+type initializerFunc func(string) error
+
+type Mounter interface {
+	Mount(target string, mounts ...mount.Mount) error
+	Unmount(target string) error
+}
+
+func InitRootFS(ctx context.Context, name string, parent digest.Digest, readonly bool, snapshotter snapshot.Snapshotter, mounter Mounter) ([]mount.Mount, error) {
+	_, err := snapshotter.Stat(ctx, name)
+	if err == nil {
+		return nil, errors.Errorf("rootfs already exists")
+	}
+	// TODO: ensure not exist error once added to snapshot package
+
+	parentS := parent.String()
+
+	initName := defaultInitializer
+	initFn := initializers[initName]
+	if initFn != nil {
+		parentS, err = createInitLayer(ctx, parentS, initName, initFn, snapshotter, mounter)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if readonly {
+		return snapshotter.View(ctx, name, parentS)
+	}
+
+	return snapshotter.Prepare(ctx, name, parentS)
+}
+
+func createInitLayer(ctx context.Context, parent, initName string, initFn func(string) error, snapshotter snapshot.Snapshotter, mounter Mounter) (string, error) {
+	initS := fmt.Sprintf("%s %s", parent, initName)
+	if _, err := snapshotter.Stat(ctx, initS); err == nil {
+		return initS, nil
+	}
+	// TODO: ensure not exist error once added to snapshot package
+
+	// Create tempdir
+	td, err := ioutil.TempDir("", "create-init-")
+	if err != nil {
+		return "", err
+	}
+	defer os.RemoveAll(td)
+
+	mounts, err := snapshotter.Prepare(ctx, td, parent)
+	if err != nil {
+		return "", err
+	}
+	defer func() {
+		if err != nil {
+			// TODO: once implemented uncomment
+			//if rerr := snapshotter.Remove(ctx, td); rerr != nil {
+			//	log.G(ctx).Errorf("Failed to remove snapshot %s: %v", td, merr)
+			//}
+		}
+	}()
+
+	if err = mounter.Mount(td, mounts...); err != nil {
+		return "", err
+	}
+
+	if err = initFn(td); err != nil {
+		if merr := mounter.Unmount(td); merr != nil {
+			log.G(ctx).Errorf("Failed to unmount %s: %v", td, merr)
+		}
+		return "", err
+	}
+
+	if err = mounter.Unmount(td); err != nil {
+		return "", err
+	}
+
+	if err := snapshotter.Commit(ctx, initS, td); err != nil {
+		return "", err
+	}
+
+	return initS, nil
+}

rootfs/init_linux.go

@@ -0,0 +1,114 @@
+package rootfs
+
+import (
+	"os"
+	"path/filepath"
+	"syscall"
+)
+
+const (
+	defaultInitializer = "linux-init"
+)
+
+func init() {
+	initializers[defaultInitializer] = initFS
+}
+
+func createDirectory(name string, uid, gid int) initializerFunc {
+	return func(root string) error {
+		dname := filepath.Join(root, name)
+		st, err := os.Stat(dname)
+		if err != nil && !os.IsNotExist(err) {
+			return err
+		} else if err == nil {
+			if st.IsDir() {
+				stat := st.Sys().(*syscall.Stat_t)
+				if int(stat.Gid) == gid && int(stat.Uid) == uid {
+					return nil
+				}
+			} else {
+				if err := os.Remove(dname); err != nil {
+					return err
+				}
+				if err := os.Mkdir(dname, 0755); err != nil {
+					return err
+				}
+			}
+		} else {
+			if err := os.Mkdir(dname, 0755); err != nil {
+				return err
+			}
+		}
+
+		return os.Chown(dname, uid, gid)
+	}
+}
+
+func touchFile(name string, uid, gid int) initializerFunc {
+	return func(root string) error {
+		fname := filepath.Join(root, name)
+
+		st, err := os.Stat(fname)
+		if err != nil && !os.IsNotExist(err) {
+			return err
+		} else if err == nil {
+			stat := st.Sys().(*syscall.Stat_t)
+			if int(stat.Gid) == gid && int(stat.Uid) == uid {
+				return nil
+			}
+			return os.Chown(fname, uid, gid)
+		}
+
+		f, err := os.OpenFile(fname, os.O_CREATE, 0644)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+
+		return f.Chown(uid, gid)
+	}
+}
+
+func symlink(oldname, newname string) initializerFunc {
+	return func(root string) error {
+		linkName := filepath.Join(root, newname)
+		if _, err := os.Stat(linkName); err != nil && !os.IsNotExist(err) {
+			return err
+		} else if err == nil {
+			return nil
+		}
+		return os.Symlink(oldname, linkName)
+	}
+}
+
+func initFS(root string) error {
+	st, err := os.Stat(root)
+	if err != nil {
+		return err
+	}
+	stat := st.Sys().(*syscall.Stat_t)
+	uid := int(stat.Uid)
+	gid := int(stat.Gid)
+
+	initFuncs := []initializerFunc{
+		createDirectory("/dev", uid, gid),
+		createDirectory("/dev/pts", uid, gid),
+		createDirectory("/dev/shm", uid, gid),
+		touchFile("/dev/console", uid, gid),
+		createDirectory("/proc", uid, gid),
+		createDirectory("/sys", uid, gid),
+		createDirectory("/etc", uid, gid),
+		touchFile("/etc/resolv.conf", uid, gid),
+		touchFile("/etc/hosts", uid, gid),
+		touchFile("/etc/hostname", uid, gid),
+		symlink("/proc/mounts", "/etc/mtab"),
+	}
+
+	for _, fn := range initFuncs {
+		if err := fn(root); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

rootfs/init_other.go

@@ -0,0 +1,7 @@
+// +build !linux
+
+package rootfs
+
+const (
+	defaultInitializer = ""
+)