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Enabling or disabling the system firewall on a Linux instance

Enabling or disabling the system firewall on a Linux instance

This topic describes how to enable or disable the system firewall on a Linux instance.

A firewall is a technology that builds a relatively isolated protective barrier between the internal network and external network of a computer (instance), thereby protecting data and information.

If the instance has the firewall enabled and has configured rules to block external access, remote connection to the instance may fail.

Prerequisites

To modify the configuration or data of an instance, we recommend that you create a snapshot to improve fault tolerance and ensure data security.

Procedure

Log in to the target instance. For operation details, refer to Logging in to Linux instances.

Commands to enable or disable the firewall vary based on the Linux system version. Select the corresponding command for your system.

CentOS 5 and CentOS 6

# Enable the firewall
service iptables start
# Disable the firewall
service iptables stop
# Check firewall running status
service iptables status

CentOS 7/Red Hat 7

# Enable the firewall
systemctl start firewalld.service
# Disable the firewall
systemctl stop firewalld.service
# Check firewall running status
firewall-cmd --state

Ubuntu

# Enable the firewall
ufw enable
# Disable the firewall
ufw disable
# Check firewall running status
ufw status

Debian

In Debian systems, you can clear a firewall policy to delete the related blocking rule. The steps are as follows:

Execute the following commands in sequence to back up the firewall policy.

touch [$Iptables]
iptables-save > [$Iptables]

tip

[$Iptables] is the backup file address of a firewall policy. Before you clear the firewall policy, back up the policy first.

Execute the following command to clear the firewall policy.

iptables -F

Last updated: 2026.06.18 17:49:51