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There is a process running in its own network namespace. I would like to telnet to the machine and run a command in this process network namespace, something like that (17543 is the pid of the process with its own network namespace):

# ip netns exec /proc/17543/ns/net ifconfig
Cannot open network namespace "/proc/17543/ns/net": No such file or directory
# ls /proc/17543/ns/net
/proc/17543/ns/net

It complains that the network namespace is not there, but it looks that the file is there. How can I run a command in another process network namespace?

wulujey
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2 Answers2

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$ sudo nsenter -t 16882 -n ip link show

where ip link show is an example of a command to run in the network namespace of the target program with pid 16882.

-t flag is for specifying the target program's pid

-n flag stands for network namespace of the target program

JenyaKh
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ip netns exec expects the name of the network namespace, not a file path.

You can find the network namespace name of a process using ip netns identify <pid>.

P.S. ifconfig may not be installed on modern Linux systems; use equivalent ip commands instead.

Michael Hampton
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    If the namespace wasn't setup with `ip netns`, then `ip netns` can't be used. Either `nsenter` is required, or mounting `/proc/17543/ns/net` at the proper place (on a dummy file in /var/run/netns/ ) to make `ip netns` believe it created it, can work. I do the later often to link a running lxc container with an `ip netns` name for convenience. – A.B Dec 12 '18 at 16:56