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<!ENTITY seealso SYSTEM "@builddir@/see_also.sgml">

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<refentry>

<docinfo><date>@LXC_GENERATE_DATE@</date></docinfo>

<refmeta>

<refentrytitle>lxc.conf</refentrytitle>

<manvolnum>5</manvolnum>

</refmeta>

<refnamediv>

<refname>lxc.conf</refname>

<refpurpose>

linux container configuration file

</refpurpose>

</refnamediv>

<refsect1>

<title>Description</title>

<para>

The linux containers (<command>lxc</command>) are always created

before being used. This creation defines a set of system

resources to be virtualized / isolated when a process is using

the container. By default, the pids, sysv ipc and mount points

are virtualized and isolated. The other system resources are

shared across containers, until they are explicitly defined in

the configuration file. For example, if there is no network

configuration, the network will be shared between the creator of

the container and the container itself, but if the network is

specified, a new network stack is created for the container and

the container can no longer use the network of its ancestor.

</para>

<para>

The configuration file defines the different system resources to

be assigned for the container. At present, the utsname, the

network, the mount points, the root file system and the control

groups are supported.

</para>

<para>

Each option in the configuration file has the form <command>key

= value</command> fitting in one line. The '#' character means

the line is a comment.

</para>

<refsect2>

<title>Hostname</title>

<para>

The utsname section defines the hostname to be set for the

container. That means the container can set its own hostname

without changing the one from the system. That makes the

hostname private for the container.

</para>

<variablelist>

<varlistentry>

<term>

<option>lxc.utsname</option>

</term>

<listitem>

<para>

specify the hostname for the container

</para>

</listitem>

</varlistentry>

</variablelist>

</refsect2>

<refsect2>

<title>Network</title>

<para>

The network section defines how the network is virtualized in

the container. The network virtualization acts at layer

two. In order to use the network virtualization, parameters

must be specified to define the network interfaces of the

container. Several virtual interfaces can be assigned and used

in a container even if the system has only one physical

network interface.

</para>

<variablelist>

<varlistentry>

<term>

<option>lxc.network.type</option>

</term>

<listitem>

<para>

specify what kind of network virtualization to be used

for the container. Each time

a <option>lxc.network.type</option> field is found a new

round of network configuration begins. In this way,

several network virtualization types can be specified

for the same container, as well as assigning several

network interfaces for one container. The different

virtualization types can be:

</para>

<para>

<option>empty:</option> will create only the loopback

interface.

</para>

<para>

<option>veth:</option> a peer network device is created

with one side assigned to the container and the other

side is attached to a bridge specified by

the <option>lxc.network.link</option>. If the bridge is

not specified, then the veth pair device will be created

but not attached to any bridge. Otherwise, the bridge

has to be setup before on the

system, <command>lxc</command> won't handle any

configuration outside of the container. By

default <command>lxc</command> choose a name for the

network device belonging to the outside of the

container, this name is handled

by <command>lxc</command>, but if you wish to handle

this name yourself, you can tell <command>lxc</command>

to set a specific name with

the <option>lxc.network.veth.pair</option> option.

</para>

<para>

<option>vlan:</option> a vlan interface is linked with

the interface specified by

the <option>lxc.network.link</option> and assigned to

the container. The vlan identifier is specified with the

option <option>lxc.network.vlan.id</option>.

</para>

<para>

<option>macvlan:</option> a macvlan interface is linked

with the interface specified by

the <option>lxc.network.link</option> and assigned to

the container.

<option>lxc.network.macvlan.mode</option> specifies the

mode the macvlan will use to communicate between

different macvlan on the same upper device. The accepted

modes are <option>private</option>, the device never

communicates with any other device on the same upper_dev (default),

<option>vepa</option>, the new Virtual Ethernet Port

Aggregator (VEPA) mode, it assumes that the adjacent

bridge returns all frames where both source and

destination are local to the macvlan port, i.e. the

bridge is set up as a reflective relay. Broadcast

frames coming in from the upper_dev get flooded to all

macvlan interfaces in VEPA mode, local frames are not

delivered locallay, or <option>bridge</option>, it

provides the behavior of a simple bridge between

different macvlan interfaces on the same port. Frames

from one interface to another one get delivered directly

and are not sent out externally. Broadcast frames get

flooded to all other bridge ports and to the external

interface, but when they come back from a reflective

relay, we don't deliver them again. Since we know all

the MAC addresses, the macvlan bridge mode does not

require learning or STP like the bridge module does.

</para>

<para>

<option>phys:</option> an already existing interface

specified by the <option>lxc.network.link</option> is

assigned to the container.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

<option>lxc.network.flags</option>

</term>

<listitem>

<para>

specify an action to do for the

network.

</para>

<para><option>up:</option> activates the interface.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

<option>lxc.network.link</option>

</term>

<listitem>

<para>

specify the interface to be used for real network

traffic.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

<option>lxc.network.name</option>

</term>

<listitem>

<para>

the interface name is dynamically allocated, but if

another name is needed because the configuration files

being used by the container use a generic name,

eg. eth0, this option will rename the interface in the

container.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

<option>lxc.network.hwaddr</option>

</term>

<listitem>

<para>

the interface mac address is dynamically allocated by

default to the virtual interface, but in some cases,

this is needed to resolve a mac address conflict or to

always have the same link-local ipv6 address

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

<option>lxc.network.ipv4</option>

</term>

<listitem>

<para>

specify the ipv4 address to assign to the virtualized

interface. Several lines specify several ipv4 addresses.

The address is in format x.y.z.t/m,

eg. 192.168.1.123/24.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

<option>lxc.network.ipv6</option>

</term>

<listitem>

<para>

specify the ipv6 address to assign to the virtualized

interface. Several lines specify several ipv6 addresses.

The address is in format x::y/m,

eg. 2003:db8:1:0:214:1234:fe0b:3596/64

</para>

</listitem>

</varlistentry>

</variablelist>

</refsect2>

<refsect2>

<title>New pseudo tty instance (devpts)</title>

<para>

For stricter isolation the container can have its own private

instance of the pseudo tty.

</para>

<variablelist>

<varlistentry>

<term>

<option>lxc.pts</option>

</term>

<listitem>

<para>

If set, the container will have a new pseudo tty

instance, making this private to it. The value specifies

the maximum number of pseudo ttys allowed for a pts

instance (this limitation is not implemented yet).

</para>

</listitem>

</varlistentry>

</variablelist>

</refsect2>

<refsect2>

<title>Console through the ttys</title>

<para>

If the container is configured with a root filesystem and the

inittab file is setup to launch a getty on the ttys. This

option will specify the number of ttys to be available for the

container. The number of getty in the inittab file of the

container should not be greater than the number of ttys

specified in this configuration file, otherwise the excess

getty sessions will die and respawn indefinitly giving

annoying messages on the console.

</para>

<variablelist>

<varlistentry>

<term>

<option>lxc.tty</option>

</term>

<listitem>

<para>

Specify the number of tty to make available to the

container.

</para>

</listitem>

</varlistentry>

</variablelist>

</refsect2>

<refsect2>

<title>Mount points</title>

<para>

The mount points section specifies the different places to be

mounted. These mount points will be private to the container

and won't be visible by the processes running outside of the

container. This is useful to mount /etc, /var or /home for

examples.

</para>

<variablelist>

<varlistentry>

<term>

<option>lxc.mount</option>

</term>

<listitem>

<para>

specify a file location in

the <filename>fstab</filename> format, containing the

mount informations.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

<option>lxc.mount.entry</option>

</term>

<listitem>

<para>

specify a mount point corresponding to a line in the

fstab format.

</para>

</listitem>

</varlistentry>

</variablelist>

</refsect2>

<refsect2>

<title>Root file system</title>

<para>

The root file system of the container can be different than that

of the host system.

</para>

<variablelist>

<varlistentry>

<term>

<option>lxc.rootfs</option>

</term>

<listitem>

<para>

specify a directory to become the root of the container.

If not specified, the container shares its root file

system with the host.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

<option>lxc.rootfs.mount</option>

</term>

<listitem>

<para>

where to recursively bind <option>lxc.rootfs</option>

before pivoting. This is to ensure success of the

<citerefentry>

<refentrytitle><command>pivot_root</command></refentrytitle>

<manvolnum>8</manvolnum>

</citerefentry>

syscall. Any directory suffices, the default should

generally work.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

<option>lxc.pivotdir</option>

</term>

<listitem>

<para>

where to pivot the original root file system under

<option>lxc.rootfs</option>, specified relatively to

that. The default is <filename>oldrootfs</filename>.

It is created if necessary, and also removed after

unmounting everything from it during container setup.

</para>

</listitem>

</varlistentry>

</variablelist>

</refsect2>

<refsect2>

<title>Control group</title>

<para>

The control group section contains the configuration for the

different subsystem. <command>lxc</command> does not check the

correctness of the subsystem name. This has the disadvantage

of not detecting configuration errors until the container is

started, but has the advantage of permitting any future

subsystem.

</para>

<variablelist>

<varlistentry>

<term>

<option>lxc.cgroup.[subsystem name]</option>

</term>

<listitem>

<para>

specify the control group value to be set. The

subsystem name is the literal name of the control group

subsystem. The permitted names and the syntax of their

values is not dictated by LXC, instead it depends on the

features of the Linux kernel running at the time the

container is started,

eg. <option>lxc.cgroup.cpuset.cpus</option>

</para>

</listitem>

</varlistentry>

</variablelist>

</refsect2>

<refsect2>

<title>Capabilities</title>

<para>

The capabilities can be dropped in the container if this one

is run as root.

</para>

<variablelist>

<varlistentry>

<term>

<option>lxc.cap.drop</option>

</term>

<listitem>

<para>

Specify the capability to be dropped in the container. A

single line defining several capabilities with a space

separation is allowed. The format is the lower case of

the capability definition without the "CAP_" prefix,

eg. CAP_SYS_MODULE should be specified as

sys_module. See

<citerefentry>

<refentrytitle><command>capabilities</command></refentrytitle>

<manvolnum>7</manvolnum>

</citerefentry>,

</para>

</listitem>

</varlistentry>

</variablelist>

</refsect2>

</refsect1>

<refsect1>

<title>Examples</title>

<para>

In addition to the few examples given below, you will find

some other examples of configuration file in @DOCDIR@/examples

</para>

<refsect2>

<title>Network</title>

<para>This configuration sets up a container to use a veth pair

device with one side plugged to a bridge br0 (which has been

configured before on the system by the administrator). The

virtual network device visible in the container is renamed to

eth0.</para>

<programlisting>

lxc.utsname = myhostname

lxc.network.type = veth

lxc.network.flags = up

lxc.network.link = br0

lxc.network.name = eth0

lxc.network.hwaddr = 4a:49:43:49:79:bf

lxc.network.ipv4 = 1.2.3.5/24

lxc.network.ipv6 = 2003:db8:1:0:214:1234:fe0b:3597

</programlisting>

</refsect2>

<refsect2>

<title>Control group</title>

<para>This configuration will setup several control groups for

the application, cpuset.cpus restricts usage of the defined cpu,

cpus.share prioritize the control group, devices.allow makes

usable the specified devices.</para>

<programlisting>

lxc.cgroup.cpuset.cpus = 0,1

lxc.cgroup.cpu.shares = 1234

lxc.cgroup.devices.deny = a

lxc.cgroup.devices.allow = c 1:3 rw

lxc.cgroup.devices.allow = b 8:0 rw

</programlisting>

</refsect2>

<refsect2>

<title>Complex configuration</title>

<para>This example show a complex configuration making a complex

network stack, using the control groups, setting a new hostname,

mounting some locations and a changing root file system.</para>

<programlisting>

lxc.utsname = complex

lxc.network.type = veth

lxc.network.flags = up

lxc.network.link = br0

lxc.network.hwaddr = 4a:49:43:49:79:bf

lxc.network.ipv4 = 1.2.3.5/24

lxc.network.ipv6 = 2003:db8:1:0:214:1234:fe0b:3597

lxc.network.ipv6 = 2003:db8:1:0:214:5432:feab:3588

lxc.network.type = macvlan

lxc.network.flags = up

lxc.network.link = eth0

lxc.network.hwaddr = 4a:49:43:49:79:bd

lxc.network.ipv4 = 1.2.3.4/24

lxc.network.ipv4 = 192.168.10.125/24

lxc.network.ipv6 = 2003:db8:1:0:214:1234:fe0b:3596

lxc.network.type = phys

lxc.network.flags = up

lxc.network.link = dummy0

lxc.network.hwaddr = 4a:49:43:49:79:ff

lxc.network.ipv4 = 1.2.3.6/24

lxc.network.ipv6 = 2003:db8:1:0:214:1234:fe0b:3297

lxc.cgroup.cpuset.cpus = 0,1

lxc.cgroup.cpu.shares = 1234

lxc.cgroup.devices.deny = a

lxc.cgroup.devices.allow = c 1:3 rw

lxc.cgroup.devices.allow = b 8:0 rw

lxc.mount = /etc/fstab.complex

lxc.mount.entry = /lib /root/myrootfs/lib none ro,bind 0 0

lxc.rootfs = /mnt/rootfs.complex

lxc.cap.drop = sys_module mknod setuid net_raw

lxc.cap.drop = mac_override

</programlisting>

</refsect2>

</refsect1>

<refsect1>

<title>See Also</title>

<simpara>

<citerefentry>

<refentrytitle><command>chroot</command></refentrytitle>

<manvolnum>1</manvolnum>

</citerefentry>,

<citerefentry>

<refentrytitle><command>pivot_root</command></refentrytitle>

<manvolnum>8</manvolnum>

</citerefentry>,

<citerefentry>

<refentrytitle><filename>fstab</filename></refentrytitle>

<manvolnum>5</manvolnum>

</citerefentry>

</simpara>

</refsect1>

&seealso;

<refsect1>

<title>Author</title>

<para>Daniel Lezcano <email>daniel.lezcano@free.fr</email></para>

</refsect1>

</refentry>