In this configuration guide, you will learn 3 ways to create a Linux Firewall Service. #centlinux #linux #firewall
Table of Contents
What is Firewalld? :
Firewalld is a firewall management tool for Linux operating systems licensed under GNU General Public License 2.
Firewalld is the default firewall management tool in RHEL based Linux distros from version 7 onwards, where it replaces the legacy firewall management tool i.e. iptables. Firewalld is a dynamically managed firewall with support for network zones, IPv4, IPv6, ethernet bridges and IP sets.
System Specification:
Consider a scenario where we are running an Oracle Database 19c instance on CentOS 8 server.
Default Oracle Listener uses the service port 1521/tcp. We have also configured another Oracle Listener service that is using port 1522/tcp.
In short, we have two Oracle listeners running on ports 1521/tcp and 1522/tcp simultaneously.
Our objective is to create a custom Linux firewall service to control access to our Oracle Listener ports.
1. Create a Linux Firewall Service using CLI:
In this method, we will create a Linux firewall service using firewall-cmd command.
Create a new service for Oracle Listener ports.
# firewall-cmd --permanent --new-service=oranet success
Add long description of the service.
# firewall-cmd --permanent --service=oranet > --set-description="Oracle Listener Service" success
Add short description of the service.
# firewall-cmd --permanent --service=oranet > --set-short=oranet success
Add Oracle Listener service ports.
# firewall-cmd --permanent --service=oranet --add-port=1521/tcp success
# firewall-cmd --permanent --service=oranet --add-port=1522/tcp success
Reload firewalld configurations.
# firewall-cmd --reload success
Display configurations of CentOS firewall.
# firewall-cmd --info-service=oranet oranet ports: 1521/tcp 1522/tcp protocols: source-ports: modules: destination:
We can add more settings to our service in similar way. You can refer to Firewalld Documentation for more details.
2. Create a Linux Firewall Service from XML file:
In this method, we will define the firewalld service settings in an XML file and then use firewall-cmd command to create a custom service in our Linux firewall.
# vi ~/oranet.xml
and add following XML code therein.
<?xml version="1.0" encoding="utf-8"?> <service> <short>oranet</short> <description>Oracle Listener Service</description> <port protocol="tcp" port="1521" /> <port protocol="tcp" port="1522" /> </service>
Now use firewall-cmd command to create Linux firewall service.
# firewall-cmd --permanent --new-service-from-file=oranet.xml success
Reload firewalld configurations and check oranet service.
# firewall-cmd --reload success
# firewall-cmd --info-service=oranet oranet ports: 1521/tcp 1522/tcp protocols: source-ports: modules: destination:
3. Create a Linux Firewall Service from Definition File:
This method is normally used by software packages during installation to create their respective firewalld services.
In this method, we create a custom service definition file in firewalld configuration directory.
# vi /etc/firewalld/services/oranet.xml
Add following XML code therein.
<?xml version="1.0" encoding="utf-8"?> <service> <short>oranet</short> <description>Oracle Listener Service</description> <port protocol="tcp" port="1521" /> <port protocol="tcp" port="1522" /> </service>
Reload firewalld configurations and check service oranet service.
# firewall-cmd --reload success
# firewall-cmd --info-service=oranet oranet ports: 1521/tcp 1522/tcp protocols: source-ports: modules: destination:
We have explored all 3 ways to create a custom service in CentOS firewall.
Conclusion:
In this configuration guide, you have learned 3 ways to create a Linux Firewall Service