Tutorial: Restoring Networking on cPanel/WHM on CloudLinux after an Automated Upgrade

If you have recently undergone an automated upgrade and reboot on your cPanel/WHM installation on CloudLinux and lost networking, you’re not alone. Here is a comprehensive guide to help you get your networking back on track.

Symptoms

You might notice:

• No internet access from your server.
• Inability to connect via SSH.
• cPanel/WHM interfaces are not loading.

Cause

This issue may arise due to incorrect network configuration settings that were overwritten or misconfigured during the upgrade.

Solution

Here’s a step-by-step guide to restore your networking:

1. Remote Access

Before you can edit any configurations, you need to access your server:

• Log in to your Linode Manager.
• Navigate to the “Remote Access” tab.

From here, make a note of your default gateway, which is usually the same as your IP address, but with the last octet set to .1 (for example, if your IP is 172.123.12.45, your gateway is likely 172.123.12.1).

2. Disable the Network Helper

This is important because it might interfere with manual configurations:

• Go to the summary page for your Linode in the Cloud Manager.
• Disable the “Network Helper”.

3. Edit Network Configuration

Now, you’ll have to manually set the network configuration:

a. Set the Default Gateway

• Open the network configuration file using the nano editor (or any other text editor you’re comfortable with):

nano /etc/sysconfig/network

• Add/modify the following lines:

NETWORKING=yes
GATEWAY=172.123.12.1  # Replace this with your actual default gateway

• Save and exit.

b. Edit the Interface Configuration

• Open the interface configuration file:

nano /etc/sysconfig/network-scripts/ifcfg-eth0

• Add/modify the following lines:

NETWORKING=yes
GATEWAY=172.123.12.1  # Again, replace this with your actual default gateway

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Troubleshooting and Additional Tips

If after following the steps above you’re still facing network connectivity issues, here are some troubleshooting steps and additional tips to help you diagnose and potentially fix the problem:

1. Verify Network Service Status

Before proceeding with more drastic measures, verify if the network service is running:

service network status

If it’s not running, try to start it:

service network start

2. Check Firewall Settings

Sometimes, a firewall may block incoming or outgoing traffic:

• List the current firewall rules:

iptables -L -n -v

• If you notice any suspicious rules that might be blocking traffic, consider disabling the firewall temporarily to see if it’s the root cause:

service iptables stop

If this fixes the issue, you’ll need to revisit your firewall rules and adjust them accordingly.

3. Inspect Network Interfaces

It might be helpful to inspect your network interfaces using:

ifconfig

Make sure your primary network interface (usually eth0) has the correct IP address and other settings.

4. Examine the Route Table

Check the routing table to ensure your default gateway is set correctly:

route -n

The gateway you’ve set should appear here.

5. Test Connectivity Locally

Ping the localhost to see if the network stack is responding:

ping 127.0.0.1

If this doesn’t work, there might be deeper issues with the system’s network stack.

6. Test Connectivity Externally

Ping a well-known address, such as one of Google’s public DNS servers:

ping 8.8.8.8

If this works, but you can’t connect to domain names (like google.com), there may be a DNS resolution issue.

7. Check DNS Settings

Inspect the /etc/resolv.conf file to see your DNS servers:

cat /etc/resolv.conf

Ensure the nameservers listed are accessible and functional.

8. Review Upgrade Logs

Review the logs related to the upgrade process. There might be clues or error messages indicating what went wrong.

cat /var/log/yum.log

This command will show you logs related to package installations and updates.

9. Consider Rolling Back

If you’ve recently taken a backup (which is always a good practice before major updates), consider rolling back to the last known good configuration.

Conclusion

Network issues can be intricate. However, with a systematic approach, they are solvable. If you’ve tried all of the above and still face issues, it might be time to reach out for professional help. Either contact Linode support, CloudLinux support, or a knowledgeable sysadmin to dive deeper into the problem. Always remember, regular backups and monitoring are essential to mitigate such challenges.