[转] Netns Beginning
11 Jun 2014一个net namespace有自己独立的路由表，iptables策略，设备管理机构，和其它的netns完全隔离。这对于做网络测试很有帮助，尤其是bridge。
Perpare
If fail with ip netns, then we have to update iproute2 to latest version.
git clone git://git.kernel.org/pub/scm/linux/kernel/git/shemminger/iproute2.git
pushd iproute2
make && make install
popd
Create / show / delete netns
ip netns add ns1
ip netns
ip netns del ns1
Attach / detach NIC to netns
Real device is not allowed to be attached, we use veth
ip link add name vethout type veth peer name vethin
Use the command to set vethin’s namespace
ip link set vethin netns ns1
To detach the veth, just ip link del .... Because veth are paired, delete one is OK
ip link del vethout
Execute commands in netns
Just ip netns exec NETNSNAME command ..., eg:
ip netns exec ns1 ifconfig -a`
Or ip netns exec ns1 bash, likes enter the namespace environment, can execute any command we like, finally use exit to leave the netns
Work with bridge
brctl addbr br0
brctl addif br0 eth0
brctl addif br0 vethout
ip link set vethout up
eth0 is a true NIC connect to a switch, by using the bridge, ns1’s vethin can connect to true network.