# phpman > man > tc-cgroup(8)

Cgroup classifier in [tc(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)                      Linux                     Cgroup classifier in [tc(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)



## NAME
       cgroup - control group based traffic control filter

## SYNOPSIS
       **tc** **filter** ... **cgroup** [ **match** _EMATCH_TREE_ ] [ **action** _ACTION_SPEC_ ]

## DESCRIPTION
       This  filter  serves  as a hint to **tc** that the assigned class ID of the net_cls control group
       the process the packet originates from belongs to should be used  for  classification.  Obvi‐
       ously, it is useful for locally generated packets only.

## OPTIONS
       **action** _ACTION_SPEC_
              Apply an action from the generic actions framework on matching packets.

       **match** _EMATCH_TREE_
              Match packets using the extended match infrastructure. See [**tc-ematch**(8)](https://www.chedong.com/phpMan.php/man/tc-ematch/8/markdown) for a detailed
              description of the allowed syntax in _EMATCH_TREE_.

## EXAMPLES
       In order to use this filter, a net_cls control group has to be created  first  and  class  as
       well as process ID(s) assigned to it. The following creates a net_cls cgroup named "foobar":

              modprobe cls_cgroup
              mkdir /sys/fs/cgroup/net_cls
              mount -t cgroup -onet_cls net_cls /sys/fs/cgroup/net_cls
              mkdir /sys/fs/cgroup/net_cls/foobar

       To  assign  a  class ID to the created cgroup, a file named _net_cls.classid_ has to be created
       which contains the class ID to be assigned as a hexadecimal, 64bit  wide  number.  The  upper
       32bits are reserved for the major handle, the remaining hold the minor. So a class ID of e.g.
       **ff:be** has to be written like so: **0xff00be** (leading zeroes may be omitted).  To  continue  the
       above example, the following assigns class ID 1:2 to foobar cgroup:

              echo 0x10002 > /sys/fs/cgroup/net_cls/foobar/net_cls.classid

       Finally some PIDs can be assigned to the given cgroup:

              echo 1234 > /sys/fs/cgroup/net_cls/foobar/tasks
              echo 5678 > /sys/fs/cgroup/net_cls/foobar/tasks

       Now  by  simply attaching a **cgroup** filter to a **qdisc** makes packets from PIDs 1234 and 5678 be
       pushed into class 1:2.


## SEE ALSO
       [**tc**(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown), [**tc-ematch**(8)](https://www.chedong.com/phpMan.php/man/tc-ematch/8/markdown),
       the file _Documentation/cgroups/net_cls.txt_ of the Linux kernel tree



iproute2                                     21 Oct 2015                  Cgroup classifier in [tc(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)