The Fortinet SSLVPN client for Linux can be downloaded on the Fortinet support portal. Linux CentOS 6.5 (32-bit & 64-bit)
Linux Ubuntu 12.0.4 (32-bit & 64-bit) are officially supported, you may also get it working on other versions and Linux flavours but don’t expect support from Fortinet for those.

The package can be found under the latest Fortigate firmware in the VPN –> SSLVPNTools subfolders. In this example I’m using the following package forticlientsslvpn_linux_4.4.2323.tar.gz with Ubuntu 15.10.

Download the SSLVPN package to your computer. Extract the forticlientsslvpn folder using Archive Manager or via cli:

$tar xvf forticlientsslvpn_linux_4.4.2323.tar.gz

The forticlientsslvpn directory contains the fortisslvpn.sh script which determines if the 32bit or 64bit binaries should be run. When executing this script via Nautilus by default it will open your text editor so it may be easiest to run the forticlientsslvpn executable within the 32bit or 64bit subdirectories. The first time the client is run you’ll be presented with a disclaimer popup and will need to enter the root password (user password with sudo privileges).

Once the disclaimer has been accepted and root password entered you’ll have the default settings.

Create a new profile by selecting “settings” and hitting “+”

Choose a name for your connection, the server, username and optionally the password. Then “create”

You should now be able to connect.

If two factor authentication is enabled an extra popup will prompt you to enter the one-time token code. Alternatively the one time token can be entered immediately following the password in the password box