src/lxc/lxc-start-ephemeral.in

	lxc-start-ephemeral.in revision 95a717e9b907de94bf29c91abca13012ec47d088
#!/usr/bin/python3
#
# lxc-start-ephemeral: Start a copy of a container using an overlay
#
# This python implementation is based on the work done in the original
# shell implementation done by Serge Hallyn in Ubuntu (and other contributors)
#
# (C) Copyright Canonical Ltd. 2012
#
# Authors:
# Stéphane Graber <stgraber@ubuntu.com>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#

# NOTE: To remove once the API is stabilized
import warnings
warnings.filterwarnings("ignore", "The python-lxc API isn't yet stable")

import argparse
import gettext
import lxc
import os
import sys
import subprocess
import tempfile

_ = gettext.gettext
gettext.textdomain("lxc-start-ephemeral")


# Other functions
def randomMAC():
    import random

    mac = [0x00, 0x16, 0x3e,
        random.randint(0x00, 0x7f),
        random.randint(0x00, 0xff),
        random.randint(0x00, 0xff)]
    return ':'.join(map(lambda x: "%02x" % x, mac))

# Begin parsing the command line
parser = argparse.ArgumentParser(
            description=_("LXC: Start an ephemeral container"),
            formatter_class=argparse.RawTextHelpFormatter, epilog=_(
"""If a COMMAND is given, then the container will run only as long
as the command runs.
If no COMMAND is given, this command will attach to tty1 and stop the
container when exiting (with ctrl-a-q).

If no COMMAND is given and -d is used, the name and IP addresses of the
container will be printed to the console."""))

parser.add_argument("--orig", "-o", type=str, required=True,
    help=_("name of the original container"))

parser.add_argument("--bdir", "-b", type=str,
    help=_("directory to bind mount into container"))

parser.add_argument("--user", "-u", type=str,
    help=_("the user to connect to the container as"))

parser.add_argument("--key", "-S", type=str,
    help=_("the path to the SSH key to use to connect"))

parser.add_argument("--daemon", "-d", action="store_true",
    help=_("run in the background"))

parser.add_argument("--union-type", "-U", type=str, default="overlayfs",
    choices=("overlayfs", "aufs"),
    help=_("type of union (overlayfs or aufs), defaults to overlayfs."))

parser.add_argument("--keep-data", "-k", action="store_true",
    help=_("Use a persistent backend instead of tmpfs."))

parser.add_argument("command", metavar='CMD', type=str, nargs="*",
    help=_("Run specific command in container (command as argument)"))

args = parser.parse_args()

# Basic requirements check
## Check that -d and CMD aren't used at the same time
if args.command and args.daemon:
    print(_("You can't use -d and a command at the same time."))
    sys.exit(1)

## The user needs to be uid 0
if not os.geteuid() == 0:
    print(_("You must be root to run this script. Try running: sudo %s" %
            (sys.argv[0])))
    sys.exit(1)

# Load the orig container
orig = lxc.Container(args.orig)
if not orig.defined:
    print(_("Source container '%s' doesn't exist." % args.orig))
    sys.exit(1)

# Create the new container paths
dest_path = tempfile.mkdtemp(prefix="%s-" % args.orig, dir="@LXCPATH@")
os.mkdir(os.path.join(dest_path, "rootfs"))

# Setup the new container's configuration
dest = lxc.Container(os.path.basename(dest_path))
dest.load_config(orig.config_file_name)
dest.set_config_item("lxc.utsname", dest.name)
dest.set_config_item("lxc.rootfs", os.path.join(dest_path, "rootfs"))
dest.set_config_item("lxc.network.hwaddr", randomMAC())

overlay_dirs = [(orig.get_config_item("lxc.rootfs"), "%s/rootfs/" % dest_path)]

# Generate a new fstab
if orig.get_config_item("lxc.mount"):
    dest.set_config_item("lxc.mount", os.path.join(dest_path, "fstab"))
    with open(orig.get_config_item("lxc.mount"), "r") as orig_fd:
        with open(dest.get_config_item("lxc.mount"), "w+") as dest_fd:
            for line in orig_fd.read().split("\n"):
                # Start by replacing any reference to the container rootfs
                line.replace(orig.get_config_item("lxc.rootfs"),
                                dest.get_config_item("lxc.rootfs"))

                # Skip any line that's not a bind mount
                fields = line.split()
                if len(fields) < 4:
                    dest_fd.write("%s\n" % line)
                    continue

                if fields[2] != "bind" and "bind" not in fields[3]:
                    dest_fd.write("%s\n" % line)
                    continue

                # Process any remaining line
                dest_mount = os.path.abspath(os.path.join("%s/rootfs/" % (
                                dest_path), fields[1]))

                if dest_mount == os.path.abspath("%s/rootfs/%s" % (
                    dest_path, args.bdir)):

                    dest_fd.write("%s\n" % line)
                    continue

                if "%s/rootfs/" % dest_path not in dest_mount:
                    print(_(
"Skipping mount entry '%s' as it's outside of the container rootfs.") % line)

                overlay_dirs += [(fields[0], dest_mount)]

# Generate pre-mount script
with open(os.path.join(dest_path, "pre-mount"), "w+") as fd:
    os.fchmod(fd.fileno(), 0o755)
    fd.write("""#!/bin/sh
LXC_DIR="%s"
LXC_BASE="%s"
LXC_NAME="%s"
""" % (dest_path, orig.name, dest.name))

    count = 0
    for entry in overlay_dirs:
        target = "%s/delta%s" % (dest_path, count)
        fd.write("mkdir -p %s %s\n" % (target, entry[1]))

        if not args.keep_data:
            fd.write("mount -n -t tmpfs none %s\n" % (target))

        if args.union_type == "overlayfs":
            fd.write("mount -n -t overlayfs"
                        " -oupperdir=%s,lowerdir=%s none %s\n" % (
                        target,
                        entry[0],
                        entry[1]))
        elif args.union_type == "aufs":
            fd.write("mount -n -t aufs "
                        "-o br=${upper}=rw:${lower}=ro,noplink none %s\n" % (
                        target,
                        entry[0],
                        entry[1]))
        count += 1

    if args.bdir:
        if not os.path.exists(args.bdir):
            print(_("Path '%s' doesn't exist, won't be bind-mounted.") %
                    args.bdir)
        else:
            src_path = os.path.abspath(args.bdir)
            dst_path = "%s/rootfs/%s" % (dest_path, os.path.abspath(args.bdir))
            fd.write("mkdir -p %s\nmount -n --bind %s %s\n" % (
                            dst_path, src_path, dst_path))

    fd.write("""
[ -e $LXC_DIR/configured ] && exit 0
for file in $LXC_DIR/rootfs/etc/hostname \\
            $LXC_DIR/rootfs/etc/hosts \\
            $LXC_DIR/rootfs/etc/sysconfig/network \\
            $LXC_DIR/rootfs/etc/sysconfig/network-scripts/ifcfg-eth0; do
        [ -f "$file" ] && sed -i -e "s/$LXC_BASE/$LXC_NAME/" $file
done
touch $LXC_DIR/configured
""")

dest.set_config_item("lxc.hook.pre-mount",
                        os.path.join(dest_path, "pre-mount"))

# Generate post-stop script
if not args.keep_data:
    with open(os.path.join(dest_path, "post-stop"), "w+") as fd:
        os.fchmod(fd.fileno(), 0o755)
        fd.write("""#!/bin/sh
[ -d "%s" ] && rm -Rf "%s"
""" % (dest.get_config_item("lxc.rootfs"), dest.get_config_item("lxc.rootfs"))

    dest.set_config_item("lxc.hook.post-stop",
                            os.path.join(dest_path, "post-stop"))

dest.save_config()

# Start the container
if not dest.start() or not dest.wait("RUNNING", timeout=5):
    print(_("The container '%s' failed to start.") % dest.name)
    dest.stop()
    if dest.defined:
        dest.destroy()
    sys.exit(1)

# Try to get the IP addresses
ips = dest.get_ips(timeout=5)

# Deal with the case where we don't start a command in the container
if not args.command:
    if args.daemon:
        print(_("""The ephemeral container is now started.

You can enter it from the command line with: lxc-console -n %s
The following IP addresses have be found in the container:
%s""") % (
                dest.name,
                "\n".join([" - %s" % entry for entry in ips]
                            or [" - %s" % _("No address could be found")])
            ))
        sys.exit(0)
    else:
        dest.console(tty=1)
        if not dest.shutdown(timeout=5):
            dest.stop()
        sys.exit(0)

# Now deal with the case where we want to run a command in the container
if not ips:
    print(_("Failed to get an IP for container '%s'.") % dest.name)
    dest.stop()
    if dest.defined:
        dest.destroy()
    sys.exit(1)

# NOTE: To replace by .attach() once the kernel supports it
cmd = ["ssh",
        "-o", "StrictHostKeyChecking=no",
        "-o", "UserKnownHostsFile=/dev/null"]

if args.user:
    cmd += ["-l", args.user]

if args.key:
    cmd += ["-k", args.key]

for ip in ips:
    ssh_cmd = cmd + [ip] + args.command
    retval = subprocess.call(ssh_cmd, universal_newlines=True)
    if retval == 255:
        print(_("SSH failed to connect, trying next IP address."))
        continue

    if retval != 0:
        print(_("Command returned with non-zero return code: %s") % retval)
    break

# Shutdown the container
if not dest.shutdown(timeout=5):
    dest.stop()