// setupNewMountNamespace is used to initialize a new mount namespace for an new
// container in the rootfs that is specified.
//
// There is no need to unmount the new mounts because as soon as the mount namespace
// is no longer in use, the mounts will be removed automatically
func setupNewMountNamespace(rootfs, console string, readonly bool) error {
// mount as slave so that the new mounts do not propagate to the host
if err := system.Mount("", "/", "", syscall.MS_SLAVE|syscall.MS_REC, ""); err != nil {
return fmt.Errorf("mounting / as slave %s", err)
}
if err := system.Mount(rootfs, rootfs, "bind", syscall.MS_BIND|syscall.MS_REC, ""); err != nil {
return fmt.Errorf("mouting %s as bind %s", rootfs, err)
}
if readonly {
if err := system.Mount(rootfs, rootfs, "bind", syscall.MS_BIND|syscall.MS_REMOUNT|syscall.MS_RDONLY|syscall.MS_REC, ""); err != nil {
return fmt.Errorf("mounting %s as readonly %s", rootfs, err)
}
}
if err := mountSystem(rootfs); err != nil {
return fmt.Errorf("mount system %s", err)
}
if err := copyDevNodes(rootfs); err != nil {
return fmt.Errorf("copy dev nodes %s", err)
}
// In non-privileged mode, this fails. Discard the error.
setupLoopbackDevices(rootfs)
if err := setupDev(rootfs); err != nil {
return err
}
if console != "" {
if err := setupPtmx(rootfs, console); err != nil {
return err
}
}
if err := system.Chdir(rootfs); err != nil {
return fmt.Errorf("chdir into %s %s", rootfs, err)
}
pivotDir, err := ioutil.TempDir(rootfs, ".pivot_root")
if err != nil {
return fmt.Errorf("can't create pivot_root dir %s", pivotDir, err)
}
if err := system.Pivotroot(rootfs, pivotDir); err != nil {
return fmt.Errorf("pivot_root %s", err)
}
if err := system.Chdir("/"); err != nil {
return fmt.Errorf("chdir / %s", err)
}
// path to pivot dir now changed, update
pivotDir = filepath.Join("/", filepath.Base(pivotDir))
if err := system.Unmount(pivotDir, syscall.MNT_DETACH); err != nil {
return fmt.Errorf("unmount pivot_root dir %s", err)
}
if err := os.Remove(pivotDir); err != nil {
return fmt.Errorf("remove pivot_root dir %s", err)
}
system.Umask(0022)
return nil
}
// remountProc is used to detach and remount the proc filesystem
// commonly needed with running a new process inside an existing container
func remountProc() error {
if err := system.Unmount("/proc", syscall.MNT_DETACH); err != nil {
return err
}
if err := system.Mount("proc", "/proc", "proc", uintptr(defaultMountFlags), ""); err != nil {
return err
}
return nil
}
func remountSys() error {
if err := system.Unmount("/sys", syscall.MNT_DETACH); err != nil {
if err != syscall.EINVAL {
return err
}
} else {
if err := system.Mount("sysfs", "/sys", "sysfs", uintptr(defaultMountFlags), ""); err != nil {
return err
}
}
return nil
}
func PivotRoot(rootfs string) error {
pivotDir, err := ioutil.TempDir(rootfs, ".pivot_root")
if err != nil {
return fmt.Errorf("can't create pivot_root dir %s", pivotDir, err)
}
if err := system.Pivotroot(rootfs, pivotDir); err != nil {
return fmt.Errorf("pivot_root %s", err)
}
if err := system.Chdir("/"); err != nil {
return fmt.Errorf("chdir / %s", err)
}
// path to pivot dir now changed, update
pivotDir = filepath.Join("/", filepath.Base(pivotDir))
if err := system.Unmount(pivotDir, syscall.MNT_DETACH); err != nil {
return fmt.Errorf("unmount pivot_root dir %s", err)
}
return os.Remove(pivotDir)
}