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Thread: OpenVPN - Cannot open TUN/TAP

  1. #1
    Join Date
    Jan 2020
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    OpenVPN - Cannot open TUN/TAP

    Hello all,
    I'm new to linux and the Ubuntu distribution to which I'm playing around and learning. I am more than at home with windows but have enough knowledge to be dangerous in linux. (I think I know what I'm doing but have no real clue).

    With that being said, my current setup is a linux container (Linux Station) on my QNAP. In an attempt to save resources, I decided to go with Ubunto 16.04 as I believe to have read some notes that its lighter weight due to GUI/Graphics requirements. I found some instructions online on how to install OpenVPN and create/configure a connection but for some reason, I cannot establish a connection. After some additional research, I found out how to view the system logs and filter them to just show the VPN Connection events/logs to which it seems I'm having trouble with a file or directory in '/dev/net/tun'. I tried to manually create this directly and set permissions (666) but the same error occurs. I have not had luck with researching this error to which I turn to the community. Please let me know if there is any information that you need and I would be happy to supply.



    SysLog:
    Jan 12 12:45:15 ubuntu_1604 NetworkManager[292]: nm-openvpn-Message: openvpn[6015] started
    Jan 12 12:45:15 ubuntu_1604 nm-openvpn[6015]: OpenVPN 2.3.10 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on Jan 9 2019
    Jan 12 12:45:15 ubuntu_1604 nm-openvpn[6015]: library versions: OpenSSL 1.0.2g 1 Mar 2016, LZO 2.08
    Jan 12 12:45:16 ubuntu_1604 nm-openvpn[6015]: NOTE: the current --script-security setting may allow this configuration to call user-defined scripts
    Jan 12 12:45:16 ubuntu_1604 nm-openvpn[6015]: NOTE: chroot will be delayed because of --client, --pull, or --up-delay
    Jan 12 12:45:16 ubuntu_1604 nm-openvpn[6015]: NOTE: UID/GID downgrade will be delayed because of --client, --pull, or --up-delay
    Jan 12 12:45:16 ubuntu_1604 nm-openvpn[6015]: UDPv4 link local: [undef]
    Jan 12 12:45:16 ubuntu_1604 nm-openvpn[6015]: UDPv4 link remote: [AF_INET]###.###.###.###:1194
    Jan 12 12:45:16 ubuntu_1604 nm-openvpn[6015]: [vpn] Peer Connection Initiated with [AF_INET]138.122.234.27:1194
    Jan 12 12:45:19 ubuntu_1604 nm-openvpn[6015]: ERROR: Cannot open TUN/TAP dev /dev/net/tun: No such file or directory (errno=2)
    Jan 12 12:45:19 ubuntu_1604 nm-openvpn[6015]: Exiting due to fatal error
    Jan 12 12:45:19 ubuntu_1604 NetworkManager[292]: (nm-openvpn-service:6007): nm-openvpn-WARNING **: openvpn[6015] exited with error code 1
    ^C

  2. #2
    Join Date
    Nov 2008
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    Metro Boston
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    14,701
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    Kubuntu Development Release

    Re: OpenVPN - Cannot open TUN/TAP

    I've seen this error before, but unfortunately the person posting the query never gave us an answer. You can read my post here: https://ubuntuforums.org/showthread....1#post13911243

    I would be surprised if you don't have /dev/net/tun though. However it is not a directory but a device. So delete whatever you put there and follow the instructions in that post to create the device. Please tell us if that resolved the problem.
    If you ask for help, do not abandon your request. Please have the courtesy to check for responses and thank the people who helped you.

    Blog · Linode System Administration Guides · Android Apps for Ubuntu Users

  3. #3
    Join Date
    Jan 2020
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    2

    Re: OpenVPN - Cannot open TUN/TAP

    I appreciate the quick reply but it didn't seem to help. I first removed the directories that I manually created by using the following commands.
    Code:
    sudo rmdir /dev/net/tun
    sudo rmdir /dev/net
    Afterwards, I tried following your steps to recreate the directory and file but VPN still won't establish a connection. I did receive a warning while following your steps
    Code:
    sudo mknod /dev/net/tun c 10 200
    "mknod: /dev/net/tun: file exists"

    I receive a slightly different error messages when trying to connect.
    ERROR: Cannot open TUN/TAP dev /dev/net/tun: Is a directory (errno=21)


    PS. When I run 'ls /dev/net" "tun" is has a green text with a green highlight. Not sure what that means or if this information is useful.
    Last edited by mpit52; 2 Weeks Ago at 08:19 PM.

  4. #4
    Join Date
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    14,701
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    Kubuntu Development Release

    Re: OpenVPN - Cannot open TUN/TAP

    On my system, /dev/net is an ordinary directory with root ownership and 755 permisssions.
    Code:
    phl@fuzzface:/dev$ ls -l | grep net
    drwxr-xr-x  2 root root          60 Jan 10 19:44 net
    /dev/net/tun is a device
    Code:
    phl@fuzzface:/dev$ ls -l net
    total 0
    crw-rw-rw- 1 root root 10, 200 Jan 10 19:44 tun
    I would remove /dev/net again, then reconstruct it and the tun device as follows:
    Code:
    cd /dev
    sudo rm -rf net
    sudo mkdir net
    cd net
    sudo mknod  tun c 10 200
    /dev/net/tun appears on my machine in green text with black reverse-video. (My terminal uses black on light yellow as the default.)
    If you ask for help, do not abandon your request. Please have the courtesy to check for responses and thank the people who helped you.

    Blog · Linode System Administration Guides · Android Apps for Ubuntu Users

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