.TH IP\-NETNS 8 "16 Jan 2013" "iproute2" "Linux"

.SH NAME

ip-netns \- process network namespace management

.SH SYNOPSIS

.sp

.ad l

.in +8

.ti -8

.B ip

.RI "[ " OPTIONS " ]"

.B netns

.RI  " { " COMMAND " | "

.BR help " }"

.sp

.ti -8

.BR "ip netns" " [ " list " ]"

.ti -8

.B ip netns add

.I NETNSNAME

.ti -8

.B ip netns attach

.I NETNSNAME PID

.ti -8

.B ip [-all] netns del

.RI "[ " NETNSNAME " ]"

.ti -8

.B ip netns set

.I NETNSNAME NETNSID

.ti -8

.IR NETNSID " := " auto " | " POSITIVE-INT

.ti -8

.BR "ip netns identify"

.RI "[ " PID " ]"

.ti -8

.BR "ip netns pids"

.I NETNSNAME

.ti -8

.BR "ip [-all] netns exec "

.RI "[ " NETNSNAME " ] " command ...

.ti -8

.BR "ip netns monitor"

.ti -8

.BR "ip netns list-id"

.RI "[ target-nsid " POSITIVE-INT " ] [ nsid " POSITIVE-INT " ]"

.SH DESCRIPTION

A network namespace is logically another copy of the network stack,

with its own routes, firewall rules, and network devices.

By default a process inherits its network namespace from its parent. Initially all

the processes share the same default network namespace from the init process.

By convention a named network namespace is an object at

.BR "@NETNS_RUN_DIR@/" NAME

that can be opened. The file descriptor resulting from opening

.BR "@NETNS_RUN_DIR@/" NAME

refers to the specified network namespace. Holding that file

descriptor open keeps the network namespace alive. The file

descriptor can be used with the

.B setns(2)

system call to change the network namespace associated with a task.

For applications that are aware of network namespaces, the convention

is to look for global network configuration files first in

.BR "@NETNS_ETC_DIR@/" NAME "/"

then in

.BR "/etc/".

For example, if you want a different version of

.BR /etc/resolv.conf

for a network namespace used to isolate your vpn you would name it

.BR @NETNS_ETC_DIR@/myvpn/resolv.conf.

.B ip netns exec

automates handling of this configuration, file convention for network

namespace unaware applications, by creating a mount namespace and

bind mounting all of the per network namespace configure files into

their traditional location in /etc.

.TP

.B ip netns list - show all of the named network namespaces

.sp

This command displays all of the network namespaces in @NETNS_RUN_DIR@

.TP

.B ip netns add NAME - create a new named network namespace

.sp

If NAME is available in @NETNS_RUN_DIR@ this command creates a new

network namespace and assigns NAME.

.TP

.B ip netns attach NAME PID - create a new named network namespace

.sp

If NAME is available in @NETNS_RUN_DIR@ this command attaches the network

namespace of the process PID to NAME as if it were created with ip netns.

.TP

.B ip [-all] netns delete [ NAME ] - delete the name of a network namespace(s)

.sp

If NAME is present in @NETNS_RUN_DIR@ it is umounted and the mount

point is removed. If this is the last user of the network namespace the

network namespace will be freed and all physical devices will be moved to the

default one, otherwise the network namespace persists until it has no more

users. ip netns delete may fail if the mount point is in use in another mount

namespace.

If

.B -all

option was specified then all the network namespace names will be removed.

It is possible to lose the physical device when it was moved to netns and

then this netns was deleted with a running process:

.RS 10

$ ip netns add net0

.RE

.RS 10

$ ip link set dev eth0 netns net0

.RE

.RS 10

$ ip netns exec net0 SOME_PROCESS_IN_BACKGROUND

.RE

.RS 10

$ ip netns del net0

.RE

.RS

and eth0 will appear in the default netns only after SOME_PROCESS_IN_BACKGROUND

will exit or will be killed. To prevent this the processes running in net0

should be killed before deleting the netns:

.RE

.RS 10

$ ip netns pids net0 | xargs kill

.RE

.RS 10

$ ip netns del net0

.RE

.TP

.B ip netns set NAME NETNSID - assign an id to a peer network namespace

.sp

This command assigns a id to a peer network namespace. This id is valid

only in the current network namespace.

If the keyword "auto" is specified an available nsid will be chosen.

This id will be used by the kernel in some netlink messages. If no id is

assigned when the kernel needs it, it will be automatically assigned by

the kernel.

Once it is assigned, it's not possible to change it.

.TP

.B ip netns identify [PID] - Report network namespaces names for process

.sp

This command walks through @NETNS_RUN_DIR@ and finds all the network

namespace names for network namespace of the specified process, if PID is

not specified then the current process will be used.

.TP

.B ip netns pids NAME - Report processes in the named network namespace

.sp

This command walks through proc and finds all of the process who have

the named network namespace as their primary network namespace.

.TP

.B ip [-all] netns exec [ NAME ] cmd ... - Run cmd in the named network namespace

.sp

This command allows applications that are network namespace unaware

to be run in something other than the default network namespace with

all of the configuration for the specified network namespace appearing

in the customary global locations. A network namespace and bind mounts

are used to move files from their network namespace specific location

to their default locations without affecting other processes.

If

.B -all

option was specified then

.B cmd

will be executed synchronously on the each named network namespace even if

.B cmd

fails on some of them. Network namespace name is printed on each

.B cmd

executing.

.TP

.B ip netns monitor - Report as network namespace names are added and deleted

.sp

This command watches network namespace name addition and deletion events

and prints a line for each event it sees.

.TP

.B ip netns list-id [target-nsid POSITIVE-INT] [nsid POSITIVE-INT] - list network namespace ids (nsid)

.sp

Network namespace ids are used to identify a peer network namespace. This

command displays nsids of the current network namespace and provides the

corresponding iproute2 netns name (from @NETNS_RUN_DIR@) if any.

The

.B target-nsid

option enables to display nsids of the specified network namespace instead of the current network

namespace. This

.B target-nsid

is a nsid from the current network namespace.

The

.B nsid

option enables to display only this nsid. It is a nsid from the current network namespace. In

combination with the

.B target-nsid

option, it enables to convert a specific nsid from the current network namespace to a nsid of the

.B target-nsid

network namespace.

.SH EXAMPLES

.PP

ip netns list

.RS

Shows the list of current named network namespaces

.RE

.PP

ip netns add vpn

.RS

Creates a network namespace and names it vpn

.RE

.PP

ip netns exec vpn ip link set lo up

.RS

Bring up the loopback interface in the vpn network namespace.

.RE

.PP

ip netns add foo

.br

ip netns add bar

.br

ip netns set foo 12

.br

ip netns set bar 13

.br

ip -n foo netns set foo 22

.br

ip -n foo netns set bar 23

.br

ip -n bar netns set foo 32

.br

ip -n bar netns set bar 33

.br

ip netns list-id target-nsid 12

.RS

Shows the list of nsids from the network namespace foo.

.RE

ip netns list-id target-nsid 12 nsid 13

.RS

Get nsid of bar from the network namespace foo (result is 23).

.RE

.SH SEE ALSO

.br

.BR ip (8)

.SH AUTHOR

Original Manpage by Eric W. Biederman

.br

Manpage revised by Nicolas Dichtel <nicolas.dichtel@6wind.com>