cml2 alpine linux command for add interface

Daniel Parker

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26-02-2025

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Alpine Linux, known for its small footprint, uses the cml2 (Control Management Layer 2) utility for network interface management. This article details how to add network interfaces to Alpine Linux using cml2. We'll cover both static and DHCP configurations. Understanding this process is crucial for setting up network connectivity on your Alpine system.

Understanding cml2

cml2 is Alpine Linux's primary tool for configuring network interfaces. Unlike systemd-networkd used in many other distributions, cml2 offers a more direct and command-line-oriented approach. This gives you precise control over your network settings. It uses configuration files located in /etc/network/.

Adding a Static IP Address with cml2

This is the most common method for configuring a network interface with a static IP address, subnet mask, gateway, and DNS servers.

1. Create the Configuration File:

First, create a configuration file for your new interface in the /etc/network/ directory. Let's say you want to add an interface named eth1:

sudo nano /etc/network/ifcfg-eth1

2. Configure the Interface:

Add the following configuration within the file, replacing the placeholder values with your actual network settings:

DEVICE=eth1
BOOTPROTO=static
IPADDR=192.168.1.100
NETMASK=255.255.255.0
GATEWAY=192.168.1.1
DNS1=8.8.8.8
DNS2=8.8.4.4

• DEVICE: The name of the network interface.
• BOOTPROTO: Specifies the method of IP address acquisition (static in this case).
• IPADDR: Your static IP address.
• NETMASK: Your subnet mask.
• GATEWAY: Your default gateway IP address.
• DNS1, DNS2: Your preferred DNS servers.

3. Apply the Changes:

After saving the file, apply the changes using cml2:

sudo cml2 start eth1

4. Verify the Configuration:

Check if the interface is up and running with the correct IP address:

ip addr show eth1

Adding a DHCP Interface with cml2

If you want the interface to obtain its IP address automatically via DHCP, the configuration is simpler:

1. Create the Configuration File:

Create a configuration file as before:

sudo nano /etc/network/ifcfg-eth1

2. Configure the Interface (DHCP):

This time, use BOOTPROTO=dhcp:

DEVICE=eth1
BOOTPROTO=dhcp

3. Apply the Changes:

Apply the changes with cml2:

sudo cml2 start eth1

4. Verify the Configuration:

Verify the interface is up and receiving an IP address via DHCP:

ip addr show eth1

Troubleshooting

• Interface not found: Ensure the interface name (eth1 in our examples) is correct. Use ip link show to list available interfaces.
• Configuration errors: Double-check your configuration file for typos or incorrect values. Even a small mistake can prevent the interface from coming up.
• Permissions: Ensure you're running the cml2 commands with sudo for appropriate permissions.
• Conflicts: Check for conflicts with other network configurations or services.

Adding Multiple Interfaces

You can repeat the above steps for additional interfaces. Just create a separate configuration file (e.g., ifcfg-wlan0 for a wireless interface) with the appropriate settings for each.

This comprehensive guide explains how to add network interfaces to Alpine Linux using cml2. Remember to always verify your configuration after making changes to ensure proper network connectivity. If you encounter issues, consult the official Alpine Linux documentation for more detailed troubleshooting information.