IP-NETNS(8) Linux IP-NETNS(8)
NAME
ip-netns - process network namespace management
SYNOPSIS
ip [ OPTIONS ] netns { COMMAND | help }
ip netns { list }
ip netns add NETNSNAME
ip [-all] netns del [ NETNSNAME ]
ip netns { set } NETNSNAME NETNSID
ip netns identify [ PID ]
ip netns pids NETNSNAME
ip [-all] netns exec [ NETNSNAME ] command...
ip netns monitor
ip netns list-id
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 /var/run/netns/NAME that can be
opened. The file descriptor resulting from opening /var/run/netns/NAME refers to the spec‐
ified 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 you want a different version of /etc/resolv.conf for a network namespace used to iso‐
late your vpn you would name it /etc/netns/myvpn/resolv.conf.
ip netns exec automates handling of this configuration, file convention for network names‐
pace 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 of the named network namespaces
This command displays all of the network namespaces in /var/run/netns
ip netns add NAME - create a new named network namespace
If NAME is available in /var/run/netns/ this command creates a new network names‐
pace and assigns NAME.
ip [-all] netns delete [ NAME ] - delete the name of a network namespace(s)
If NAME is present in /var/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 net‐
work 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
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 - assign an id to a peer network namespace
This command assigns a id to a peer network namespace. This id is valid only in the
current network namespace. This id will be used by the kernel in some netlink mes‐
sages. 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 network namespaces names for process
This command walks through /var/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 processes in the named network namespace
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 ] cmd ... - Run cmd in the named network namespace
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 names‐
pace specific location to their default locations without affecting other pro‐
cesses.
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.
ip netns monitor - Report as network namespace names are added and deleted
This command watches network namespace name addition and deletion events and prints
a line for each event it sees.
ip netns list-id - list network namespace ids (nsid)
Network namespace ids are used to identify a peer network namespace. This command
displays nsid of the current network namespace and provides the corresponding
iproute2 netns name (from /var/run/netns) if any.
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.
SEE ALSO
ip(8)
AUTHOR
Original Manpage by Eric W. Biederman
iproute2 16 Jan 2013 IP-NETNS(8)
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