In this article will be covering details regarding iptables and firewalld which helps in Linux
firewall management. We will also be looking at how to enable specific ports (1521 for Oracle) inside iptables. Linux Firewall Status Linux Disable Firewall Linux Enable Firewall Enable Ports in Linux The Linux firewalld command will let you check Linux firewall status. It will show you the current status Active in case firewall is running For practicing Oracle on Linux, you might need to stop the Linux firewall so that
you can connect applications to database listener. Below commands will permanently disable Linux firewall Just in case you would like to enable Linux firewall after disabling it, use below commands On some servers, port 1521
will not be enabled by default because of security reasons. You can enable this specific port inside linux using below commands. If you are working on Oracle Linux 5 or 6 version, use Linux iptables command to enable specific ports as root user If you would like to open any specific port in Linux, just replace the port number (1521) with new port number. To open multiple port ranges in Linux, use below command In
some Linux versions, below command works fineRead more about Linux iptables vs Linux firewall
Linux Firewall status
Linux Disable Firewall
Linux Enable Firewall
Enable Ports in Linux
Enable 1521 Port in Linux
Enable Port Range in Linux
Enable Port in Oracle Linux 7
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The firewall service, firewalld, is installed on the system by default. Use the firewalld CLI interface to check that the service is running. To see the status of the service: For more information
about the service status, use the systemctl status sub-command: Furthermore, it is important to know how firewalld is set up and which rules are in force before you try to edit the settings. To display the firewall settings, see Section 5.3.2, “Viewing Current firewalld
Settings”5.3.1. Viewing the Current Status of firewalld
5.3.2. Viewing Current firewalld Settings
5.3.2.1. Viewing Allowed Services using GUI
To view the list of services using the graphical firewall-config tool, press the Super key to enter the Activities Overview, type firewall, and press Enter. The firewall-config tool appears. You can now view the list of services under the tab.
Alternatively, to start the graphical firewall configuration tool using the command-line, enter the following command:
~]$ firewall-configThe Firewall Configuration window opens. Note that this command can be run as a normal user, but you are prompted for an administrator password occasionally.
Figure 5.2. The Services tab in firewall-config
5.3.2.2. Viewing firewalld Settings using CLI
With the CLI client, it is possible to get different views of the current firewall settings. The --list-all option shows a complete overview of the firewalld settings.
firewalld uses zones to manage the traffic. If a zone is not specified by the --zone option, the command is effective in the default zone assigned to the active network interface and connection.
To list all the relevant information for the default zone:
~]# firewall-cmd --list-all public target: default icmp-block-inversion: no interfaces: sources: services: ssh dhcpv6-client ports: protocols: masquerade: no forward-ports: source-ports: icmp-blocks: rich rules:To specify the zone for which to display the settings, add the --zone=zone-name argument to the firewall-cmd --list-all command, for example:
~]# firewall-cmd --list-all --zone=home home target: default icmp-block-inversion: no interfaces: sources: services: ssh mdns samba-client dhcpv6-client ... [output truncated]To see the settings for particular information, such as services or ports, use a specific option. See the firewalld manual pages or get a list of the options using the command help:
~]# firewall-cmd --help Usage: firewall-cmd [OPTIONS...] General Options -h, --help Prints a short help text and exists -V, --version Print the version string of firewalld -q, --quiet Do not print status messages Status Options --state Return and print firewalld state --reload Reload firewall and keep state information ... [output truncated]For example, to see which services are allowed in the current zone:
~]# firewall-cmd --list-services ssh dhcpv6-clientListing the settings for a certain subpart using the CLI tool can sometimes be difficult to interpret. For example, you allow the SSH service and firewalld opens the necessary port (22) for the service. Later, if you list the allowed services, the list shows the SSH service, but if you list open ports, it does not show any. Therefore, it is recommended to use the --list-all option to make sure you receive a complete information.
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