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Managing iptables as a Service and Integrating with Docker

firewall iptables

Reference: https://upcloud.com/resources/tutorials/configure-iptables-centos

Problem: Non-persistent iptables rule after system restarts.

This is how to add a rule to iptables:

sudo iptables -A INPUT -p tcp --dport ssh -j ACCEPT

Solution:

This command applies the rule immediately, but it won’t persist after a system restart.

To make iptables rules persistent, follow these steps:

  1. Install iptables-services:
sudo yum install iptables-services
  1. Start and enable iptables:
sudo systemctl start iptables
sudo systemctl enable iptables
  1. Save the current rules to a file:
sudo iptables-save > /etc/sysconfig/iptables

To restore the rules, you can either restart iptables or use iptables-restore:

sudo iptables-restore < /etc/sysconfig/iptables

If you need to manage iptables rules alongside Docker, remember:

  1. Always restart iptables before Docker:
sudo systemctl restart iptables
sudo systemctl restart docker

  1. If you need to add custom rules to iptables for Docker containers, use the DOCKER-USER chain. This chain is designed to allow user-defined rules.

  2. To add a custom rule to the DOCKER-USER chain, for example, allowing HTTP access to Docker containers:

sudo iptables -A DOCKER-USER -p tcp --dport 80 -j ACCEPT
  1. Save and restore the rules to ensure persistence across system restarts:
sudo iptables-save > /etc/sysconfig/iptables
sudo systemctl restart iptables
sudo systemctl restart docker

By following these practices, we can manage iptables rules effectively while preventing conflicts with Docker’s automatic iptables management. This approach ensures a seamless integration of iptables with Docker and maintains the security of the system.