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 specified network names-
pace. 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 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 names-
pace 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 namespace and assigns NAME.
ip [-all] netns delete [ NAME ] - delete the name of a network names-
pace(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 network
namespace persists until it has no more users. ip netns delete
may fail if the mount point is in use in another mount names-
pace.
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 pre-
vent 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 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 network namespaces names for process
This command walks through /var/run/netns and finds all the net-
work 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 names-
pace.
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 net-
work 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 loca-
tions without affecting other processes.
If -all option was specified then cmd will be executed syn-
chronously 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 dele-
tion 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 names-
pace. This command displays nsid of the current network names-
pace 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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