Tip: How to start OpenVPN server when systemd based service start to refuse on boot

Posted on in Categories Howto, Open Source, Security last updated February 5, 2017

For some weird reason, I can not get my OpenVPN server to come up at boot time using systemd on an Ubuntu Linux 16.04 LTS server. I have tried a few settings but failed so far.

So I twitted about it:


Here is my /lib/systemd/system/openvpn.service file:
# cat /lib/systemd/system/openvpn.service 

# This service is actually a systemd target,
# but we are using a service since targets cannot be reloaded.
 
[Unit]
Description=OpenVPN service
After=network.target
 
[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/bin/true
ExecReload=/bin/true
WorkingDirectory=/etc/openvpn
 
[Install]
WantedBy=multi-user.target

I wanted to run services after the network is up so that OpenVPN can bind to specific IP and port. The After=network.target tells to wait until the nework is “up”.

My fix

I finally gave up and simply wrote cron job that will start after each system reboot:
@reboot sleep 100;/etc/init.d/openvpn restart;/etc/init.d/ssh restart;/etc/init.d/squid reload
The @reboot forces to run job once, at startup. In this case, restart the openvpn server, and bind sshd/squid to openvpn port:
$ ss -tulpn
OR
$ netstat -tulpn
Sample outputs:

tcp        0      0 10.8.0.1:80             0.0.0.0:*               LISTEN      1549/lighttpd   
tcp        0      0 0.0.0.0:53              0.0.0.0:*               LISTEN      1524/dnsmasq    
tcp        0      0 10.8.0.1:22             0.0.0.0:*               LISTEN      1756/sshd       
tcp        0      0 10.8.0.1:3128           0.0.0.0:*               LISTEN      1675/(squid-1)  
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN      1732/openvpn

There must be a way to run services (OpenVPN) after the network is up. However, I failed to figure it out. If anyone knows how to fix this problem without using cron, let me know in the comments section below.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

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  3. Vivek: Problem with openvpn and related services that bind to ip addresses are that it is started before network interface has assigned ip address.
    So, fix is very simple.

    You must:
    1. Enable NetworkManager-wait-online.service, or systemd-networkd-wait-online.service (depend which type you use)
    systemctl enable NetworkManager-wait-online.service
    or
    systemctl enable systemd-networkd-wait-online.service

    2. Tell openvpn service to start after network interfaces has ip addresses (after start network-online.target, which is started after NetworkManager-wait-online.service or systemd-networkd-wait-online.service), so add/change these to lines to service file to [Unit] section:
    [Unit]
    After=network-online.target
    Wants=network-online.target

    3. Don’t update openvpn service file directly in /lib directory, but make a local copy to /etc:
    sudo cp /lib/systemd/system/openvpn.service /etc/systemd/system/openvpn.service
    sudo vim /etc/systemd/system/openvpn.service
    4. Finally reload systemd daemon:
    sudo systemctl daemon-reload
    5. Check if openvpn.service symlink in directory /etc/systemd/system/multi-user.target.wants/ is pointed to /etc service file (copy), not to /lib, so:
    openvpn.service -> /etc/systemd/system/openvpn.service
    If not, simple disable and enable openvpn.service, so it point to right file:
    sudo systemctl disable openvpn.service && sudo systemctl enable openvpn.service
    5. Restart computer, and openvpn will start after network

    2. I had this issue before, even after the solution above. Netnomada is right about the service trying to bind to an IP not yet available and his solution will fix the issue in most installations.

      You’ll run into issues if you’ve IPv6 enabled, in that case, the solution won’t work because your system will run IPv6 DAD (duplicate address detection) and there’s an old bug where the IP won’t be available but the network-online.target would be fired.

      I reported that issue here: https://github.com/systemd/systemd/issues/2037 and seems to be patched. However it might take some time to get to your system.

      Tld;dr: apply the solution above and if you’ve IPv6, DAD might become an issue, disable it with net.ipv6.conf.eth0.accept_dad = 0 at /etc/sysctl.conf

    3. Instead of copying the whole file, you could just add a “fragment” file:

      mkdir /etc/systemd/system/openvpn.service.d
      cat </etc/systemd/system/openvpn.service.d/wait-online.conf
      [Unit]
      After=network-online.target
      Wants=network-online.target
      << EOF

  4. Same with me. Had to rc.local it. In my case it’s an openvz VPS. I’ve seen some people saying the same problem occurs with LXD.

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