Function pivot_root

src/linux/fs.cpp:587–622

Try<Nothing> pivot_root(
    const string& newRoot,
    const string& putOld)
{
  // These checks are done in the syscall but we'll do them here to
  // provide less cryptic error messages. See 'man 2 pivot_root'.
  if (!os::stat::isdir(newRoot)) {
    return Error("newRoot '" + newRoot + "' is not a directory");
  }

  if (!os::stat::isdir(putOld)) {
    return Error("putOld '" + putOld + "' is not a directory");
  }

  // TODO(idownes): Verify that newRoot (and putOld) is on a different
  // filesystem to the current root. st_dev distinguishes the device
  // an inode is on, but bind mounts (which are acceptable to
  // pivot_root) share the same st_dev as the source of the mount so
  // st_dev is not generally sufficient.

  if (!strings::startsWith(putOld, newRoot)) {
    return Error("putOld '" + putOld +
                 "' must be beneath newRoot '" + newRoot);
  }

#ifdef __NR_pivot_root
  int ret = ::syscall(__NR_pivot_root, newRoot.c_str(), putOld.c_str());
#else
#error "pivot_root is not available"
#endif
  if (ret == -1) {
    return ErrnoError();
  }

  return Nothing();
}


namespace chroot {