How to let the entries in fstab to be mounted after VPN become up?

2 min read 24-10-2024

the ifix

How to let the entries in fstab to be mounted after VPN become up?

When working with a VPN (Virtual Private Network), you may encounter situations where you need specific file systems or directories to be mounted only after the VPN is established. This is particularly useful when you're accessing network resources that are only available when connected to the VPN. In this article, we'll explore how to achieve this by configuring the fstab file and adjusting some network settings.

Original Code Scenario

The original problem may look like this:

# /etc/fstab
192.168.1.100:/data /mnt/data nfs defaults 0 0

This fstab entry aims to mount an NFS share from a server with the IP address 192.168.1.100 to the local directory /mnt/data. However, if the VPN is not active, this mount will fail because the server is unreachable.

Understanding the Problem

To solve this issue, we need to ensure that the entries in the fstab file are only mounted after the VPN connection is established. This requires some additional configuration since the standard fstab mount behavior does not account for VPN connections.

Step-by-Step Solution

Identify VPN Connection: The first step is to determine how to know when your VPN connection is up. This can usually be done with a script that checks the status of the VPN interface.
Create a Custom Script: Write a script that mounts the necessary file systems only after the VPN connection is established. For example, you can create a script like this:
```
#!/bin/bash

# Check if the VPN is active
if ifconfig | grep 'tun0' > /dev/null; then
    mount -a
else
    echo "VPN is not connected."
fi
```
In this script, tun0 represents the typical name for a VPN interface. You may need to modify it based on your system's VPN configuration.
Automate with Systemd: To ensure that the script runs after the VPN connection is established, you can create a systemd service. Here’s how to do that:
- Create a new service file in /etc/systemd/system/mount-after-vpn.service.
```
[Unit]
Description=Mount fstab entries after VPN
Requires=your-vpn.service
After=your-vpn.service

[Service]
Type=oneshot
ExecStart=/path/to/your/script.sh
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target
```
Replace your-vpn.service with the name of your actual VPN service, and point ExecStart to the path of the script you created.
Enable the Service: Run the following command to enable your new service:
```
sudo systemctl enable mount-after-vpn.service
```

Practical Example

To illustrate this, let's consider a practical example. Suppose you work for a company that provides an NFS share containing important documents. This share is only accessible via a VPN. Using the steps outlined above, you can ensure that every time you connect to your VPN, the NFS share is automatically mounted, allowing you easy access to your work files.

Conclusion

By leveraging scripts and systemd services, you can effectively manage how your fstab entries are mounted in relation to your VPN connection. This process allows for a seamless workflow, reducing the need for manual mounting and ensuring you are always connected to the resources you need.

Additional Resources

Implementing these steps will greatly enhance your productivity, particularly if your work heavily depends on network resources accessed through a VPN. Happy mounting!