Lesson 1

Serial and networking devices are essential for the administration of any Linux system. These devices, which include both physical and virtual interfaces, facilitate the necessary communication channels for data exchange and network connectivity. In Red Hat Enterprise Linux (RHEL) 9.2, there are specific tools and protocols used to manage these devices effectively.

Serial devices in RHEL can be configured through a couple of different methods, the most common being through the use of the setserial command.

1. Setserial Command: This command is used to get or set Linux serial port information. It's typically used in a startup script for setting the parameters of serial ports that are needed for your hardware. Example usage:
   

   # setserial /dev/ttyS0 baud_base 38400 spd_hi
   

   
   Here, /dev/ttyS0 is the first serial port, the baud_base is set to 38400, and the spd_hi option sets the port speed to twice the speed of the baud_base. Remember, you must have the appropriate system privileges to use the setserial command, typically requiring root access.

In RHEL 9.2, networking devices are configured and managed using the NetworkManager service, the nmcli command-line tool, and the nmtui text user interface tool.

1. NetworkManager Service: This is a dynamic network control and configuration system that attempts to keep network devices and connections up and active when they are available. It's primarily controlled using the nmcli and nmtui tools, but you can also check its status with the systemctl command:
   

   # systemctl status NetworkManager
   

2. Nmcli Tool: This is a command-line client for NetworkManager. It is used to create, display, edit, delete, activate, and deactivate network connections, as well as control and display network device status. For example, to display all connections, you would use:
   

   # nmcli con show
   

   
   To bring up a connection named 'Wired connection 1', you'd use:
   

   # nmcli con up "Wired connection 1"
   

3. Nmtui Tool: This is a text user interface tool for NetworkManager. While not as flexible as the command-line tool, it provides a straightforward and user-friendly way to create, edit, and delete network connections. You can start it with the nmtui command:
   

   # nmtui
   

   From there, you'll be presented with a menu that allows you to Edit a connection, Activate a connection, and Set the system hostname.

Note: It's important to remember that in order to make any substantial changes to the network or serial configurations, you will need root privileges. Always ensure that your changes are tested and validated to prevent any possible network interruptions or connectivity issues.

Also remember that managing your networking also often involves managing your firewall, as it can control what traffic is allowed to enter or leave your network. RHEL 9.2 uses firewalld for this, which can be managed using the firewall-cmd tool.
The commands provided here are just a basic introduction. There are many more options and advanced configurations available with these tools, and you should refer to the man pages (man setserial, man nmcli, man nmtui, man firewall-cmd) and the official Red Hat documentation for more detailed information.

Connecting to other computers and networks is one of the most powerful aspects of computing. Without external access, basic functions such as email and file sharing cannot be performed. To enable users to access information available outside their local machines, Linux supports communication with other computers over telephone lines and networks. In this module, you will learn how to enable and update serial and non-serial devices using Linux commands and utilities, including the setserial command, the getty program and its variants, and the Network Configurator. You will also investigate differences between serial and non-serial devices in support, configuration, and use.

After completing this module, you will be able to:

1. Describe some of the serial devices supported by Red Hat Linux
2. Configure and use serial ports
3. Define a modem's role in a Linux system
4. Describe the rationale for using multiple network interface cards
5. Load the correct NIC modules into the kernel to enable multiple network interface cards
6. Use the Network Configurator tool to enable multiple network interface cards

Networking connectivity: To connect your Linux system to a network, Linux offers support for a variety of Local Area Network (LAN) boards, modems, and serial devices. In addition to LAN protocols, such as Ethernet and Token Ring protocols, all the most popular upper level networking protocols can be built-in. The most popular of these protocols is TCP/IP (used to connect to the Internet). Other protocols, such as IPX (for Novell networks) and X.25 (a packet-switching network type that is popular in Europe), are also available.
Network servers: Providing networking services to the client computers on the LAN or to the entire Internet is what Linux does best. A variety of software packages are available that enable you to use Linux as a print server, file server, FTP server, mail server, Web server, news server, or workgroup (bootp or NIS) server.
Application support: Because of compatibility with POSIX and several different application programming interfaces (APIs), a wide range of freeware and shareware software is available for Linux. Most GNU software from the Free Software Foundation will run in Linux.
The next lesson describes some of the serial devices supported by Red Hat Linux.