Provided by: lxc_0.6.5-1_i386 bug


       lxc.conf - linux container configuration file


       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

       Each  option in the configuration file has the form key = value fitting
       in one line. The ’#’ character means the line is a comment.

       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.

              specify the hostname for the container

       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.

              specify what kind of network virtualization to be used  for  the
              container.  Each  time  a 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  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

              vlan: a vlan interface is linked with the interface specified by
              the and assigned to  the  container.  The  vlan
              identifier is specified with the option

              macvlan:  a  macvlan  interface  is  linked  with  the interface
              specified by the and assigned to the container.
     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
     is assigned to the container.

              specify an action to do for the network.

              up: activates the interface.

              specify the interface to be used for real network traffic.

              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.

              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

              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.

              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

       For  stricter isolation the container can have its own private instance
       of the pseudo tty.

              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).

       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.

              Specify the number of tty to make available to the container.

       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.

              specify a file location in  the  fstab  format,  containing  the
              mount informations.

              specify  a  mount  point  corresponding  to  a line in the fstab

       The root file system is the location where the container will chroot.

              specify a file location containing the new file tree for a  root
              file system.

       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.

       The capabilities can be dropped in the container if this one is run  as

              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),


       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 = veth = up = br0 = eth0 = 4a:49:43:49:79:bf = = 2003:db8:1:0:214:1234:fe0b:3597

       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

       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

       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 the root file system.

       lxc.utsname = complex = veth = up = br0 = 4a:49:43:49:79:bf = = 2003:db8:1:0:214:1234:fe0b:3597 = 2003:db8:1:0:214:5432:feab:3588 = macvlan = up = eth0 = 4a:49:43:49:79:bd = = = 2003:db8:1:0:214:1234:fe0b:3596 = phys = up = dummy0 = 4a:49:43:49:79:ff = = 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


       chroot(1), pivot_root(8), fstab(5)


       lxc(1),  lxc-create(1), lxc-destroy(1), lxc-start(1), lxc-stop(1), lxc-
       execute(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),


       Daniel Lezcano <>

                                22 January 2010                    LXC.CONF(5)