IP-NETNS(8) (16 Jan 2013) IP-NETNS(8)
NAME
ip-netns - process network namespace management
SYNOPSIS
ip [ OPTIONS ] netns { COMMAND | help }
ip netns [ list ]
ip netns add NETNSNAME
ip netns attach NETNSNAME PID
ip [-all] netns del [ NETNSNAME ]
ip netns set NETNSNAME NETNSID
NETNSID := auto | POSITIVE-INT
ip netns identify [ PID ]
ip netns pids NETNSNAME
ip [-all] netns exec [ NETNSNAME ] command...
ip netns monitor
ip netns list-id [ target-nsid POSITIVE-INT ] [ nsid
POSITIVE-INT ]
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
/run/netns/NAME that can be opened. The file descriptor
resulting from opening /run/netns/NAME refers to the speci-
fied network namespace. Holding that file descriptor open
keeps the network namespace alive. The file descriptor can
be used with the 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 /etc/netns/NAME/ then in /etc/. For example, if
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you want a different version of /etc/resolv.conf for a net-
work namespace used to isolate your vpn you would name it
/etc/netns/myvpn/resolv.conf.
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.
ip netns list - show all
This command displays all of the network namespaces in
/run/netns
ip netns add NAME - create
If NAME is available in /run/netns this command creates
a new network namespace and assigns NAME.
ip netns attach NAME PID -
If NAME is available in /run/netns this command
attaches the network namespace of the process PID to
NAME as if it were created with ip netns.
ip [-all] netns delete [ NAME
If NAME is present in /run/netns 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 -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:
$ ip netns add net0
$ ip link set dev eth0 netns net0
$ ip netns exec net0 SOME_PROCESS_IN_BACKGROUND
$ ip netns del net0
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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:
$ ip netns pids net0 | xargs kill
$ ip netns del net0
ip netns set NAME NETNSID -
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.
ip netns identify [PID] - Report
This command walks through /run/netns 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.
ip netns pids NAME - Report
This command walks through proc and finds all of the
process who have the named network namespace as their
primary network namespace.
ip [-all] netns exec [ NAME
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 -all option was specified then cmd will be executed
synchronously on the each named network namespace even
if cmd fails on some of them. Network namespace name is
printed on each cmd executing.
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ip netns monitor - Report as
This command watches network namespace name addition
and deletion events and prints a line for each event it
sees.
ip netns list-id [target-nsid POSITIVE-INT] [nsid
Network namespace ids are used to identify a peer net-
work namespace. This command displays nsids of the cur-
rent network namespace and provides the corresponding
iproute2 netns name (from /run/netns) if any.
The target-nsid option enables to display nsids of the
specified network namespace instead of the current net-
work namespace. This target-nsid is a nsid from the
current network namespace.
The nsid option enables to display only this nsid. It
is a nsid from the current network namespace. In combi-
nation with the target-nsid option, it enables to con-
vert a specific nsid from the current network namespace
to a nsid of the target-nsid network namespace.
EXAMPLES
ip netns list
Shows the list of current named network namespaces
ip netns add vpn
Creates a network namespace and names it vpn
ip netns exec vpn ip link set lo up
Bring up the loopback interface in the vpn network
namespace.
ip netns add foo
ip netns add bar
ip netns set foo 12
ip netns set bar 13
ip -n foo netns set foo 22
ip -n foo netns set bar 23
ip -n bar netns set foo 32
ip -n bar netns set bar 33
ip netns list-id target-nsid 12
Shows the list of nsids from the network namespace foo.
ip netns list-id target-nsid 12 nsid 13
Get nsid of bar from the network namespace foo (result
is 23).
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SEE ALSO
ip(8)
AUTHOR
Original Manpage by Eric W. Biederman
Manpage revised by Nicolas Dichtel
<nicolas.dichtel@6wind.com>
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