1.OpenVPN for most commercial VPN providers)

Setting up a VPN on Ubuntu via the command line (shell) can be done using various methods, depending on the VPN protocol (e.g., OpenVPN, WireGuard, or IPsec). Below are instructions for common VPN setups: Many VPN providers (e.g., NordVPN, ProtonVPN) offer .ovpn configuration files.

Install OpenVPN

sudo apt update
sudo apt install openvpn

Download VPN Configuration

Get .ovpn files from your VPN provider (usually from their website), then place them in /etc/openvpn/:

sudo cp ~/Downloads/your-vpn-config.ovpn /etc/openvpn/client.conf

Start the VPN

sudo systemctl start openvpn@client

Enable Auto-Start (Optional)

sudo systemctl enable openvpn@client

Check Connection

ip a show tun0  # Check if tun0 interface exists
curl ifconfig.me  # Check your public IP

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WireGuard (Modern & Fast VPN)

WireGuard is lightweight and often faster than OpenVPN.

Install WireGuard

sudo apt update
sudo apt install wireguard resolvconf

Generate Keys

cd /etc/wireguard/
umask 077  # Restrict file permissions
wg genkey | tee privatekey | wg pubkey > publickey

Configure WireGuard

Create /etc/wireguard/wg0.conf (replace with your VPN provider's config):

[Interface]
PrivateKey = <your_private_key>
Address = 10.0.0.2/24
DNS = 1.1.1.1
[Peer]
PublicKey = <server_public_key>
Endpoint = vpn.example.com:51820
AllowedIPs = 0.0.0.0/0

Start WireGuard

sudo wg-quick up wg0

Enable Auto-Start

sudo systemctl enable wg-quick@wg0

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IPsec VPN (for Enterprise VPNs)

For IPsec (e.g., Cisco VPN), use strongSwan.

Install strongSwan

sudo apt install strongswan

Configure /etc/ipsec.conf

Example config (adjust as needed):

conn myvpn
    keyexchange=ikev2
    ike=aes256-sha256-modp2048!
    esp=aes256-sha256!
    left=%config
    leftsourceip=%config
    right=vpn.example.com
    rightid=@vpn.example.com
    auto=start

Start the VPN

sudo ipsec start
sudo ipsec up myvpn

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Disconnect VPN

• OpenVPN: sudo systemctl stop openvpn@client
• WireGuard: sudo wg-quick down wg0
• IPsec: sudo ipsec down myvpn

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Troubleshooting

• Permissions: Ensure config files are readable only by root (chmod 600).
• Logs: Check logs with journalctl -u openvpn@client or sudo wg show.
• Firewall: Allow VPN ports (e.g., UDP 1194 for OpenVPN, UDP 51820 for WireGuard).

Let me know if you need help with a specific VPN provider or protocol!