Mount on VPN Connect

I use a VPN to my server from my laptop which can happen from effectively "anywhere". But I also don't always want to connect to my server so I use the KDE Network Manager to manually connect with through GUI only when needed. This causes issues when it comes to mounting remote drives because the server isn't always available.

This is my solution for an adhoc drive mount over and unpredictable VPN connection. This uses Systemd due to its ability to add dependencies which make it more robust. I'm also only going to be covering SMB. In my experience NFS is inferior in performance consistency even in an all Linux environment.

Starting Point

On your server you need to setup a typical Samba setup[1]. Make sure you can mount your share on your client computer using other methods like mount or /etc/fstab.

I'm also going to be using Wireguard[2] but there isn't anything unique to that for this setup. Note we do not need proxy forwarding for this.

VPN Network Interface Target

In order to prevent the mounts from attempting to access the server when it is unreachable we need to set the VPN connection as a dependancy of the Systemd mount. This is not the same as network-online.target. We can use a specific network interface as a target, but you need to find what yours is called.

You can list all targetable NICs for Systemd using the following command:

systemctl list-units --no-pager | grep net-device

You'll be given a result similar to this:

sys-subsystem-net-devices-docker0.device                 loaded active plugged   /sys/subsystem/net/devices/docker0
sys-subsystem-net-devices-enp45s0.device                 loaded active plugged   Killer E3000 2.5GbE Controller
sys-subsystem-net-devices-enx9cebe850e460.device         loaded active plugged   Dell D3100 Docking Station

The list can be much longer depending on your system. To more easily find your VPN interface you can run the command before and after connecting and look for the new line that will be added. For reference, here is how my Wireguard connection was shown:

sys-subsystem-net-devices-Videos\x2dLocal.device         loaded active plugged   /sys/subsystem/net/devices/Videos-Local

I will be using sys-subsystem-net-devices-Videos\x2dLocal.device as my target for service unit scripts.

Systemd Mount and Automount

Systemd can manage the mounting of filesystems as unit files. These are just plain text files that are easily configurable for different needed. On Ubuntu as an example they are located in /etc/systemd/system/. We are going to make a mount and automount service for each share you want to mount to after connecting to the VPN.

Mount Service File

The SMB/CIFS settings for the mount go in the mount script. The settings you need for this will be dependent on your server setup but the one I'm using here are a decent general purpose solution.

opt-videos.mount

[Unit] Description=SMB Share OnFailure=automount-restarter@%N.service [Mount] # Server share path over VPN What=//10.0.10.1/videos # Local mount directory Where=/opt/videos # SMB mount options Options=credentials=/etc/smb.conf,vers=3.1.1,uid=1000,iocharset=utf8 Type=cifs TimeoutSec=30

Some notes about different settings in there:

• credentials : The path to a file that stores the user auth for connecting to the samba server[3]
• uid : The user ID number for the user on the server you want the file modifications to be saved as.
• opt-videos.mount : The filename for the unit file must match the path set in Where=

We'll get to OnFailure below as it is a workaround for a Systemd quirk, you will need it though.

Automount Service File

The mount file earlier lacks an [Install] directive meaning it is never run. The automount file does and by sharing the same filename will watch for filesystem access of the mount path to automatically call the mount file. It also has the dependencies to know to run only after the network interface is connected.

opt-videos.automount

[Unit] Description=SMB Share Automount OnFailure=automount-restarter@%N.service # Network interface target dependancies After=sys-subsystem-net-devices-Videos\x2dLocal.device Requisite=sys-subsystem-net-devices-Videos\x2dLocal.device [Automount] Where=/opt/videos [Install] WantedBy=multi-user.target

Self Starting

automount-restarter@%N.service

[Unit] Description=automount restarter for %i [Service] Type=oneshot ExecStartPre=/usr/bin/sleep 10 ExecStart=/usr/bin/systemctl restart %i.automount