Troubleshooting: Cannot open TUN/TAP dev /dev/net/tun

If you are getting error ‘Cannot open TUN/TAP dev /dev/net/tun‘ while starting OpenVPN server, it means that you should load ‘tun’ module which features TUN/TAP device driver:

OpenVPN 2.1.1 i386-redhat-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] built on Jan 26 2010
NOTE: the current –script-security setting may allow this configuration to call user-defined scripts
LZO compression initialized
Note: Cannot open TUN/TAP dev /dev/net/tun: No such device (errno=19)
Note: Attempting fallback to kernel 2.2 TUN/TAP interface
Cannot allocate TUN/TAP dev dynamically

To load module you should use modprobe command:

modprobe tun

If no error apeared you will be able to check it with lsmod:

[root@server1 ~]# lsmod | grep tun
tun 14455 2
[root@server1 ~]#

Afetr that you can start OpenVPN server:

[root@server1 ~]# /etc/init.d/openvpn start
Starting openvpn:                                             [ OK ]
[root@server1 ~]#

Note that if you use OpenVZ -based VPS you might need to contact your provider or enable it in control panel.

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