# Copyright 2015 The Chromium Authors. All rights reserved. # Use of this source code is governed by a BSD-style license that can be # found in the LICENSE file. """This module provides some utilities used by LXC and its tools. """ import collections import os import shutil import tempfile from contextlib import contextmanager import common from autotest_lib.client.bin import utils from autotest_lib.client.common_lib import error from autotest_lib.client.common_lib.cros.network import interface from autotest_lib.site_utils.lxc import constants def path_exists(path): """Check if path exists. If the process is not running with root user, os.path.exists may fail to check if a path owned by root user exists. This function uses command `test -e` to check if path exists. @param path: Path to check if it exists. @return: True if path exists, otherwise False. """ try: utils.run('sudo test -e "%s"' % path) return True except error.CmdError: return False def get_host_ip(): """Get the IP address of the host running containers on lxcbr*. This function gets the IP address on network interface lxcbr*. The assumption is that lxc uses the network interface started with "lxcbr". @return: IP address of the host running containers. """ # The kernel publishes symlinks to various network devices in /sys. result = utils.run('ls /sys/class/net', ignore_status=True) # filter out empty strings interface_names = [x for x in result.stdout.split() if x] lxc_network = None for name in interface_names: if name.startswith('lxcbr'): lxc_network = name break if not lxc_network: raise error.ContainerError('Failed to find network interface used by ' 'lxc. All existing interfaces are: %s' % interface_names) netif = interface.Interface(lxc_network) return netif.ipv4_address def clone(lxc_path, src_name, new_path, dst_name, snapshot): """Clones a container. @param lxc_path: The LXC path of the source container. @param src_name: The name of the source container. @param new_path: The LXC path of the destination container. @param dst_name: The name of the destination container. @param snapshot: Whether or not to create a snapshot clone. """ snapshot_arg = '-s' if snapshot and constants.SUPPORT_SNAPSHOT_CLONE else '' # overlayfs is the default clone backend storage. However it is not # supported in Ganeti yet. Use aufs as the alternative. aufs_arg = '-B aufs' if utils.is_vm() and snapshot else '' cmd = (('sudo lxc-clone --lxcpath {lxcpath} --newpath {newpath} ' '--orig {orig} --new {new} {snapshot} {backing}') .format( lxcpath = lxc_path, newpath = new_path, orig = src_name, new = dst_name, snapshot = snapshot_arg, backing = aufs_arg )) utils.run(cmd) @contextmanager def TempDir(*args, **kwargs): """Context manager for creating a temporary directory.""" tmpdir = tempfile.mkdtemp(*args, **kwargs) try: yield tmpdir finally: shutil.rmtree(tmpdir) class BindMount(object): """Manages setup and cleanup of bind-mounts.""" def __init__(self, spec): """Sets up a new bind mount. Do not call this directly, use the create or from_existing class methods. @param spec: A two-element tuple (dir, mountpoint) where dir is the location of an existing directory, and mountpoint is the path under that directory to the desired mount point. """ self.spec = spec def __eq__(self, rhs): if isinstance(rhs, self.__class__): return self.spec == rhs.spec return NotImplemented def __ne__(self, rhs): return not (self == rhs) @classmethod def create(cls, src, dst, rename=None, readonly=False): """Creates a new bind mount. @param src: The path of the source file/dir. @param dst: The destination directory. The new mount point will be ${dst}/${src} unless renamed. If the mount point does not already exist, it will be created. @param rename: An optional path to rename the mount. If provided, the mount point will be ${dst}/${rename} instead of ${dst}/${src}. @param readonly: If True, the mount will be read-only. False by default. @return An object representing the bind-mount, which can be used to clean it up later. """ spec = (dst, (rename if rename else src).lstrip(os.path.sep)) full_dst = os.path.join(*list(spec)) if not path_exists(full_dst): utils.run('sudo mkdir -p %s' % full_dst) utils.run('sudo mount --bind %s %s' % (src, full_dst)) if readonly: utils.run('sudo mount -o remount,ro,bind %s' % full_dst) return cls(spec) @classmethod def from_existing(cls, host_dir, mount_point): """Creates a BindMount for an existing mount point. @param host_dir: Path of the host dir hosting the bind-mount. @param mount_point: Full path to the mount point (including the host dir). @return An object representing the bind-mount, which can be used to clean it up later. """ spec = (host_dir, os.path.relpath(mount_point, host_dir)) return cls(spec) def cleanup(self): """Cleans up the bind-mount. Unmounts the destination, and deletes it if possible. If it was mounted alongside important files, it will not be deleted. """ full_dst = os.path.join(*list(self.spec)) utils.run('sudo umount %s' % full_dst) # Ignore errors because bind mount locations are sometimes nested # alongside actual file content (e.g. SSPs install into # /usr/local/autotest so rmdir -p will fail for any mounts located in # /usr/local/autotest). utils.run('sudo bash -c "cd %s; rmdir -p --ignore-fail-on-non-empty %s"' % self.spec) MountInfo = collections.namedtuple('MountInfo', ['root', 'mount_point', 'tags']) def get_mount_info(mount_point=None): """Retrieves information about currently mounted file systems. @param mount_point: (optional) The mount point (a path). If this is provided, only information about the given mount point is returned. If this is omitted, info about all mount points is returned. @return A generator yielding one MountInfo object for each relevant mount found in /proc/self/mountinfo. """ with open('/proc/self/mountinfo') as f: for line in f.readlines(): # These lines are formatted according to the proc(5) manpage. # Sample line: # 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root \ # rw,errors=continue # Fields (descriptions omitted for fields we don't care about) # 3: the root of the mount. # 4: the mount point. # 5: mount options. # 6: tags. There can be more than one of these. This is where # shared mounts are indicated. # 7: a dash separator marking the end of the tags. mountinfo = line.split() if mount_point is None or mountinfo[4] == mount_point: tags = [] for field in mountinfo[6:]: if field == '-': break tags.append(field.split(':')[0]) yield MountInfo(root = mountinfo[3], mount_point = mountinfo[4], tags = tags) def is_subdir(parent, subdir): """Determines whether the given subdir exists under the given parent dir. @param parent: The parent directory. @param subdir: The subdirectory. @return True if the subdir exists under the parent dir, False otherwise. """ # Append a trailing path separator because commonprefix basically just # performs a prefix string comparison. parent = os.path.join(parent, '') return os.path.commonprefix([parent, subdir]) == parent