There area unit some vital security updates area unit through with the OpenVPN version a pair of.4 compared with 2.3. therefore if you're victimisation the previous version, you'll be able to upgrade it to 2.4 by keeping this configurations as well as the files, certificates, and alternative settings.

How to Upgrade OpenVPN version 2.3 to 2.4 on Debian or Ubuntu

Here i'm providing the steps to try to to the upgrade:

1. Backup the current configuration files for safety. 
2. Check the current version using the command:

   # openvpn --version

3. Import the public GPG key that is used to sign the packages:

   # wget -O - https://swupdate.openvpn.net/repos/repo-public.gpg|apt-key add -

4. Create a new source list to find the updated OpenVPN packages:

   # echo "deb http://build.openvpn.net/debian/openvpn/<version> <osrelease> main" > /etc/apt/sources.list.d/openvpn-aptrepo.list 

Where the <version> can be one of the following:

stable: stable releases only - no alphas, betas or RCs

testing: latest releases, including alphas/betas/RCs

release/2.3: OpenVPN 2.3 releases

release/2.4: OpenVPN 2.4 releases, including alphas/betas/RCs

Replace <osrelease> with the required one from the above list.

The area <osrelease> depends your distribution:

wheezy 

jessie

precise 

trusty 

xenial

You can check it from your OS and use the appropriate one.

Eg: # echo "deb http://build.openvpn.net/debian/openvpn/stable jessie main" > /etc/apt/sources.list.d/openvpn-aptrepo.list

5. Run an update.

# apt-get update

6. The upgrade the OpenVPN package:

# apt-get --only-upgrade install openvpn

7. Once the upgrade is done, please verify the new version and also check if the old configurations are still there.