Running OpenVPN on Ubuntu without root privileges is challenging because OpenVPN typically requires root to create network interfaces (e.g., tun/tap). However, you can achieve this using Apptainer (formerly Singularity) to run OpenVPN in a container with the necessary permissions, even as a non-root user. Here’s how:

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Method: Run OpenVPN in an Apptainer Container

Apptainer allows you to run containers with elevated privileges (e.g., --fakeroot or --userns) without requiring root on the host system.

Prerequisites

1. Apptainer installed on your Ubuntu system. If not, install it:

   bash
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   sudo apt update && sudo apt install -y apptainer

2. OpenVPN configuration files (.ovpn or .conf) for your VPN provider.
3. User namespace support enabled on your system (usually is by default on Ubuntu).

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Step 1: Create an Apptainer Container for OpenVPN

You can use a pre-built OpenVPN image or create a custom one.

Option A: Use a Pre-Built OpenVPN Image

Pull an OpenVPN image from a trusted source (e.g., Docker Hub via Apptainer):

bash
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apptainer pull docker://kylemanna/openvpn

This will create a .sif file (e.g., openvpn_latest.sif).

Option B: Build a Custom OpenVPN Container

Create a definition file (openvpn.def) to build a custom container:

bash
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Bootstrap: docker
From: ubuntu:22.04

%post
    apt update && apt install -y openvpn
    mkdir -p /etc/openvpn

Then build the container:

bash
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apptainer build openvpn.sif openvpn.def

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Step 2: Copy VPN Configuration Files

Place your .ovpn or .conf files in a directory (e.g., ~/vpn-config) and ensure they are readable by your user.

Example:

bash
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mkdir -p ~/vpn-config
cp /path/to/your/config.ovpn ~/vpn-config/

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Step 3: Run OpenVPN in the Container

Use Apptainer to run the container with the following flags:

• --fakeroot: Simulates root inside the container (required for OpenVPN).
• --bind: Mount your VPN config directory into the container.
• --network=host: Allows the container to use the host’s network stack.

bash
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apptainer run --fakeroot --bind ~/vpn-config:/etc/openvpn --network=host openvpn.sif openvpn --config /etc/openvpn/config.ovpn

Explanation of Flags:

• --fakeroot: Allows OpenVPN to run as "root" inside the container.
• --bind ~/vpn-config:/etc/openvpn: Binds your local config directory to /etc/openvpn in the container.
• --network=host: Ensures the container can create network interfaces.

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Step 4: Verify the Connection

Check if the VPN is active:

bash
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ip a show tun0

Or test connectivity:

bash
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curl ifconfig.me

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Alternative: Use slirp4netns for Network Isolation

If --network=host is not allowed, use slirp4netns for user-mode networking:

bash
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apptainer run --fakeroot --bind ~/vpn-config:/etc/openvpn --network=slirp4netns openvpn.sif openvpn --config /etc/openvpn/config.ovpn

This is slower but works in restricted environments.

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Troubleshooting

1. Permission Errors: Ensure your user has access to /dev/net/tun:

   bash
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   sudo chmod 666 /dev/net/tun

   Or add your user to the tun group:

   bash
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   sudo usermod -aG tun $USER

2. Apptainer Errors: If Apptainer complains about --fakeroot, ensure your kernel supports user namespaces:

   bash
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   sudo sysctl -w kernel.unprivileged_userns_clone=1

3. OpenVPN Logs: Add --verb 4 to the OpenVPN command for detailed logs:

   bash
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   openvpn --config /etc/openvpn/config.ovpn --verb 4

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Security Notes

• Running OpenVPN in a container with --fakeroot is not as secure as running it natively as root. Use this only in trusted environments.
• Avoid binding sensitive host directories (e.g., /etc, /root) into the container.

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Summary

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Would you like help creating a custom OpenVPN configuration or debugging a specific issue?