iptables: rules lost after reboot

iptables: rules lost after reboot

iptables rules disappear after a system reboot because they are stored in memory and not saved to a persistent configuration file.

When iptables Produces This Error

After rebooting the server, iptables -L shows an empty ruleset or only default ACCEPT policies. All custom rules — port openings, NAT, rate limits — are gone.

What Causes iptables Rules to Be Lost After Reboot

iptables stores rules in kernel memory. When the system reboots, the kernel reinitializes and the rules are cleared. Unlike nftables (which reads /etc/nftables.conf at boot), iptables has no built-in persistence mechanism.

How to Fix iptables Rules Lost After Reboot

1. Install iptables-persistent on Ubuntu/Debian:

   sudo apt install iptables-persistent

2. Save the current rules:

   sudo iptables-save | sudo tee /etc/iptables/rules.v4

3. Verify the rules load on boot by rebooting and checking:

   sudo reboot
   # After reboot:
   sudo iptables -L -n

How to Verify the Fix

After reboot, iptables -L -n should display the saved rules.