How to load tun module in linux?

This answer is probably a bit late, but I ran into the problem, exactly as described, myself.

Running OpenVPN would produce:

Note: Cannot open TUN/TAP dev /dev/net/tun: No such file or directory (errno=2)

And running tunctl would produce:

Failed to open '/dev/net/tun' : No such file or directory

And this command had no output:

lsmod | grep tun

When attempting to add the tun module via:

modprobe tun

modprobe would exit with a failure error code (1), and nothing changed.

I found an alternate way of activating the tun module via insmod. First locate the module with this command:

find /lib/modules/ -iname 'tun.ko.gz'

Then use insmod with the returned path (I only got one match), for example:

insmod /lib/modules/3.6.9-1-ARCH/kernel/drivers/net/tun.ko.gz

For me, running that command worked, and tunctl and OpenVPN worked okay afterwards.

I ran into a similar problem when trying to run openvpn on OVH Cloud VPS, openvpn complains that cannot find TUN interface.

modprobe will always return module not found :

$ sudo modprobe tun
FATAL: Module tun not found.

Finally, I found that tun is not a module but built in kernel, so what I do to solve was created the missing dir and nod:

$ sudo mkdir /dev/net
$ sudo mknod /dev/net/tun c 10 200

And then openvpn can find and use the tun device.

To be noted that afterward, modprobe will still return an error, because tun is not a module.

$ sudo modprobe tun
FATAL: Module tun not found.

In Arch linux installing the networkmanager-vpnc package will solve the problem