Implement containers
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""" Container objects """
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from . import settings
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from . import util
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from .xml_template import XMLTemplate
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import libvirt
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import tempfile
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import subprocess
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from pathlib import Path
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import getpass
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import weakref
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class OverlayDirectory:
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""" Allocates an overlayfs with a given lower dir and a temporary upper dir. The
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overlayfs is destroyed when this object is deallocated """
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class DoesNotExist(Exception):
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""" Raised if `lower` does not exist """
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def __init__(self, path):
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self.path = path
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def __str__(self):
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return "Path {} does not exist".format(self.path)
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def __init__(self, lower, name=None):
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if not name:
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name = ""
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self.lower = Path(lower)
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if not self.lower.exists():
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raise self.DoesNotExist(self.lower)
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root_temp_dir = Path(settings.OVERLAYFS_BASE_DIR)
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if not root_temp_dir.exists():
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root_temp_dir.mkdir()
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self.overlay_temp_dir = tempfile.TemporaryDirectory(
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prefix=name + ("_" if name else ""), dir=root_temp_dir.resolve(),
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)
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self.temp_dir = Path(self.overlay_temp_dir.name)
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self.temp_dir_cleaner = None
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self.upper = self.temp_dir / "upper"
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self.work = self.temp_dir / "work"
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self.mount_point = self.temp_dir / "mount"
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self.upper.mkdir()
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self.work.mkdir()
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self.mount_point.mkdir()
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self.mounted = False
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self._mount()
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def _mount(self):
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if self.mounted:
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return
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command = [
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"sudo",
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"mount",
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"-t",
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"overlay",
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"overlay",
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"-o",
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"lowerdir={lower},upperdir={upper},workdir={work}".format(
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lower=self.lower.resolve(),
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upper=self.upper.resolve(),
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work=self.work.resolve(),
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),
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self.mount_point,
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]
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subprocess.run(command)
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self.mounted = True
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self.temp_dir_cleaner = weakref.finalize(
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self.overlay_temp_dir, self.cleanup_mount
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)
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def _umount(self):
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if not self.mounted:
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return
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command = [
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"sudo",
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"umount",
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self.mount_point,
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]
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subprocess.run(command)
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self.mounted = False
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def _set_perms_for_cleanup(self):
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""" Sets the permissions to allow cleanup """
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if not self.temp_dir.exists():
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return # Already deleted
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# The overlayfs runs as root, so we need to allow our current user to delete
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# the temp directory files
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command_chown = [
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"sudo",
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"chown",
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"-R",
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getpass.getuser(),
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self.temp_dir.resolve(),
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]
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subprocess.run(command_chown)
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command_chmod = [
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"sudo",
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"chmod",
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"-R",
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"700",
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self.temp_dir.resolve(),
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]
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subprocess.run(command_chmod)
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def cleanup_mount(self):
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self._umount()
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self._set_perms_for_cleanup()
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class Container(util.LibvirtObject):
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class AlreadyExists(Exception):
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def __str__(self):
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return "This container is already instanciated"
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def __init__(self, conn, networks, name=None, mem=int(1e6)):
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super().__init__(conn)
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if not name:
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name = str(self.id)
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self.name = settings.PREFIX + "_dom_" + name
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self.networks = networks
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self.mem = mem
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self.overlay_root = None
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self.lxc_container = None
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def get_jinja_networks(self):
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""" Get a jinja2 environment-compatible network list """
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return [
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{"mac": util.MACAddress(net.id, self.id), "name": net.name, "net": net}
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for net in self.networks
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]
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def create(self):
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if self.lxc_container:
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raise self.AlreadyExists()
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self.overlay_root = OverlayDirectory(settings.BASE_SYSTEM_ROOT, name=self.name)
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xml = XMLTemplate("container.xml").inst(
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name=self.name,
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uuid=self.uuid,
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mem=self.mem,
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filesystem_root=self.overlay_root.mount_point,
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networks=self.get_jinja_networks(),
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)
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self.lxc_container = self.conn.createXML(xml)
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def cleanup(self):
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if self.lxc_container:
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try:
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self.lxc_container.destroy()
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except libvirt.libvirtError as exn:
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if not str(exn).startswith("Domain not found:"):
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raise exn
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# Else, the machine was already stopped: everything is fine
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def __enter__(self):
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self.create()
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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self.cleanup()
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def __del__(self):
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self.cleanup()
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@ -7,7 +7,10 @@ PREFIX = "testnw"
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CONTAINER_BASE_ROOT = "/var/lib/machines/lxc-base-" + PREFIX
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# Overlayfs mount dir
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OVERLAYFS_MOUNT_DIR = "/tmp/{}-overlays/".format(PREFIX)
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OVERLAYFS_BASE_DIR = "/tmp/{}-overlays/".format(PREFIX)
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# Base root
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BASE_SYSTEM_ROOT = "/home/tobast/Machines/lxc-network/_base"
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# The ID of the whole generated network -- below 0xff
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NETWORK_ID = 132
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@ -0,0 +1,36 @@
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<domain type="lxc">
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<name>{{ name }}</name>
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<uuid>{{ uuid }}</uuid>
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<memory unit="KiB">{{ mem }}</memory>
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<vcpu placement="static">1</vcpu>
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<os>
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<type arch="x86_64">exe</type>
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<init>/sbin/init</init>
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</os>
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<features>
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<privnet/>
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</features>
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<clock offset="utc"/>
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<on_poweroff>destroy</on_poweroff>
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<on_reboot>restart</on_reboot>
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<on_crash>destroy</on_crash>
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<devices>
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<emulator>/usr/lib/libvirt/libvirt_lxc</emulator>
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<filesystem type="mount" accessmode="mapped">
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<source dir="{{ filesystem_root }}"/>
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<target dir="/"/>
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</filesystem>
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{% for net in networks %}
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<interface type="network">
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<mac address="{{ net.mac }}"/>
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<source network="{{ net.name }}"/>
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</interface>
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{% endfor %}
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<console type="pty">
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<target type="lxc" port="0"/>
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</console>
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</devices>
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</domain>
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