How to Connect to Wi-Fi Using `wpa_supplicant` on Arch Linux

Arch Linux is a lightweight and flexible Linux distribution aimed at more experienced users who enjoy building their system from the ground up. When it comes to networking, Arch gives you full control — including the ability to connect to Wi-Fi networks manually without relying on graphical utilities or network managers.

One of the most powerful tools for managing wireless networks in a command-line environment is wpa_supplicant. This article provides a comprehensive, step-by-step guide on how to connect to a Wi-Fi network using wpa_supplicant on Arch Linux.

Why Use wpa_supplicant?

Before diving in, it’s helpful to understand why one might choose wpa_supplicant over a GUI-based solution:

• Minimalist Setup: Ideal for servers, headless systems, or minimal desktop environments.
• Full Control: You configure and control every aspect of the connection.
• No Bloat: Avoid installing full network managers like NetworkManager or ConnMan.
• Learning Opportunity: You gain a deeper understanding of how Linux handles wireless networking.

Prerequisites

Before starting, make sure your system meets the following requirements:

1. A Wireless Interface

Run the following to list your network interfaces:

ip link

Wireless interfaces are usually named wlan0, wlp2s0, or something similar, depending on your hardware and naming scheme.

2. Required Packages

Ensure the necessary packages are installed:

sudo pacman -Syu wpa_supplicant wireless_tools dialog iw

Explanation of each package:

• wpa_supplicant: The main daemon that handles WPA/WPA2 authentication.
• wireless_tools: Utilities like iwconfig.
• dialog: Provides text-based GUI elements (used by wifi-menu).
• iw: Modern utility for configuring wireless devices.

Step-by-Step Guide to Connect Using wpa_supplicant

Step 1: Bring Up the Wireless Interface

First, check if your wireless device is recognized and enabled:

ip link show

If your wireless interface (say, wlp2s0) is down, bring it up:

sudo ip link set wlp2s0 up

Use your interface name in place of wlp2s0.

Step 2: Scan for Available Networks

Use iw to scan for available Wi-Fi networks:

sudo iw dev wlp2s0 scan | less

This command returns a lot of data, but you’re looking for lines like:

SSID: YourNetworkName

Note the SSID of the network you want to connect to.

Step 3: Create a WPA Configuration File

You’ll need a configuration file for wpa_supplicant. You can generate one using wpa_passphrase:

wpa_passphrase "YourNetworkName" "YourPassword"

Example:

wpa_passphrase "HomeWiFi" "StrongPass123"

This will output:

network={
    ssid="HomeWiFi"
    #psk="StrongPass123"
    psk=7e0c9a60d82b2f0000d0b3df87fcfd49f84e27e0dfebf2ddfd019e67c4b8cbfc
}

Redirect the output to a file:

wpa_passphrase "HomeWiFi" "StrongPass123" | sudo tee /etc/wpa_supplicant/wpa_supplicant.conf

Step 4: Start wpa_supplicant

Now you can start wpa_supplicant with the correct options. The basic syntax is:

sudo wpa_supplicant -B -i wlp2s0 -c /etc/wpa_supplicant/wpa_supplicant.conf

Explanation:

• -B: Run in the background.
• -i: Interface to use.
• -c: Path to the configuration file.

Check the output of:

sudo journalctl -u wpa_supplicant

To ensure the connection process started correctly.

Step 5: Obtain an IP Address

Once authenticated, you need to get an IP address using a DHCP client:

sudo dhcpcd wlp2s0

Alternatively, you can use:

sudo dhclient wlp2s0

Depending on which DHCP client you prefer (make sure it’s installed).

To verify connectivity:

ping archlinux.org

If you receive replies, you’re online!

Optional: Run as a Systemd Service

If you want wpa_supplicant to connect automatically at boot, you can enable it as a systemd service.

Step 1: Create a Service File (Optional)

You can use the built-in service file:

sudo systemctl enable wpa_supplicant@wlp2s0.service

And start it with:

sudo systemctl start wpa_supplicant@wlp2s0.service

This will automatically read the default config file at /etc/wpa_supplicant/wpa_supplicant.conf.

Step 2: Enable DHCP at Boot

Also enable a DHCP client to get an IP address automatically:

sudo systemctl enable dhcpcd@wlp2s0.service

Or if you’re using systemd-networkd, configure that instead.

Troubleshooting

Problem: Could not read interface or No such device

Make sure your interface is listed and brought up using:

ip link set wlp2s0 up

If still not found, you may need firmware drivers for your Wi-Fi chip. Check the output of:

dmesg | grep firmware

Install firmware packages such as linux-firmware or specific ones like broadcom-wl.

Problem: No IP Address After Connecting

After wpa_supplicant succeeds, make sure you’ve requested an IP:

sudo dhcpcd wlp2s0

Or check ip a to see if an address was assigned.

Problem: Authentication Fails

• Double-check your SSID and password.
• Ensure no typos in the wpa_supplicant.conf.
• Look for errors in:

sudo journalctl -xeu wpa_supplicant

Advanced Options

Using a Temporary Config File

You don’t have to save a config to disk. This is useful for testing:

wpa_passphrase "MySSID" "MyPassword" > temp.conf
sudo wpa_supplicant -B -i wlp2s0 -c temp.conf

Open Networks (No Password)

For open networks, create a minimal config like:

network={
    ssid="OpenWiFi"
    key_mgmt=NONE
}

Save it and use it with wpa_supplicant.

Wrapping Up

Connecting to Wi-Fi using wpa_supplicant on Arch Linux may seem intimidating at first, but it’s a powerful and transparent method that grants full control over your system’s network behavior. Whether you’re managing a headless device or simply prefer command-line tools, mastering wpa_supplicant is a valuable skill for any Arch Linux user.

To recap:

1. Bring up the interface.
2. Scan for networks.
3. Create a wpa_supplicant config.
4. Start wpa_supplicant.
5. Obtain an IP address via DHCP.
6. Optionally, automate the process with systemd services.

Arch’s philosophy of simplicity and user-centric control shines through in how it handles networking. By learning to use wpa_supplicant, you’re aligning with the Arch way — and becoming a more knowledgeable Linux user in the process.