Add init and get mounts to rootfs service

Update rootfs package to add mount initializer function.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

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
+}