After a recent upgrade to Debian Stretch, my OpenVPN server stopped working. Checking the relevant log file,
/var/log/openvpn.log, I found the following not very helpful error message.
Fri Nov 23 16:46:37 2018 OpenVPN 2.4.0 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [PKCS11] [MH/PKTINFO] [AEAD] built on Jul 18 2017 Fri Nov 23 16:46:37 2018 library versions: OpenSSL 1.0.2l 25 May 2017, LZO 2.08 Fri Nov 23 16:46:37 2018 daemon() failed or unsupported: Resource temporarily unavailable (errno=11) Fri Nov 23 16:46:37 2018 Exiting due to fatal error
Fortunately, someone already reported this error to debian and found out that the error is caused by the
LimintNPROC directive in systemd is used to limit the number of forks a service is allowed to make. Removing this limit, might not be the best idea. So, I would suggest that instead of commenting it out, to find out the minimal value that allows OpenVPN to start and work. After some testing, I found that the minimal value that worked for me is
After editing the
/lib/systemd/system/openvpn@.service, you need to reload the systemd service files and restart the OpenVPN server process.
$ sudo systemctl daemon-reload $ sudo systemctl restart openvpn@server