NAME
lxc.conf - linux container configuration file
DESCRIPTION
The linux containers (lxc) 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.
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.
Each option in the configuration file has the form key = value fitting
in one line. The '#' character means the line is a comment.
HOSTNAME
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.
lxc.utsname
specify the hostname for the container
NETWORK
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.
lxc.network.type
specify what kind of network virtualization to be used for the
container. Each time a lxc.network.type 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:
empty: will create only the loopback interface.
veth: 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 lxc.network.link. 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, lxc won't handle any configuration outside
of the container. By default lxc choose a name for the network
device belonging to the outside of the container, this name is
handled by lxc, but if you wish to handle this name yourself,
you can tell lxc to set a specific name with the
lxc.network.veth.pair option.
vlan: a vlan interface is linked with the interface specified by
the lxc.network.link and assigned to the container. The vlan
identifier is specified with the option lxc.network.vlan.id.
macvlan: a macvlan interface is linked with the interface
specified by the lxc.network.link and assigned to the container.
lxc.network.macvlan.mode specifies the mode the macvlan will use
to communicate between different macvlan on the same upper
device. The accepted modes are private, the device never
communicates with any other device on the same upper_dev
(default), vepa, 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 bridge, 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.
phys: an already existing interface specified by the
lxc.network.link is assigned to the container.
lxc.network.flags
specify an action to do for the network.
up: activates the interface.
lxc.network.link
specify the interface to be used for real network traffic.
lxc.network.name
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.
lxc.network.hwaddr
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
lxc.network.ipv4
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.
lxc.network.ipv6
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
NEW PSEUDO TTY INSTANCE (DEVPTS)
For stricter isolation the container can have its own private instance
of the pseudo tty.
lxc.pts
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).
CONTAINER SYSTEM CONSOLE
If the container is configured with a root filesystem and the inittab
file is setup to use the console, you may want to specify where goes
the output of this console.
lxc.console
Specify a path to a file where the console output will be
written.
CONSOLE THROUGH THE TTYS
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.
lxc.tty
Specify the number of tty to make available to the container.
MOUNT POINTS
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.
lxc.mount
specify a file location in the fstab format, containing the
mount informations.
lxc.mount.entry
specify a mount point corresponding to a line in the fstab
format.
ROOT FILE SYSTEM
The root file system of the container can be different than that of the
host system.
lxc.rootfs
specify a directory to become the root of the container. If not
specified, the container shares its root file system with the
host.
lxc.rootfs.mount
where to recursively bind lxc.rootfs before pivoting. This is
to ensure success of the pivot_root(8) syscall. Any directory
suffices, the default should generally work.
lxc.pivotdir
where to pivot the original root file system under lxc.rootfs,
specified relatively to that. The default is mnt. It is
created if necessary, and also removed after unmounting
everything from it during container setup.
CONTROL GROUP
The control group section contains the configuration for the different
subsystem. lxc 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.
lxc.cgroup.[subsystem name]
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.
lxc.cgroup.cpuset.cpus
CAPABILITIES
The capabilities can be dropped in the container if this one is run as
root.
lxc.cap.drop
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 capabilities(7),
EXAMPLES
In addition to the few examples given below, you will find some other
examples of configuration file in /usr/share/doc/lxc/examples
NETWORK
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.
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
CONTROL GROUP
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.
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
COMPLEX CONFIGURATION
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.
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
SEE ALSO
chroot(1), pivot_root(8), fstab(5)
SEE ALSO
lxc(1), lxc-create(1), lxc-destroy(1), lxc-start(1), lxc-stop(1), lxc-
execute(1), lxc-kill(1), lxc-console(1), lxc-monitor(1), lxc-wait(1),
lxc-cgroup(1), lxc-ls(1), lxc-ps(1), lxc-info(1), lxc-freeze(1), lxc-
unfreeze(1), lxc.conf(5)
AUTHOR
Daniel Lezcano <daniel.lezcano@free.fr>
26 July 2010