Networking

Connecting your computer to the Internet is one of the most important aspects of networking. Connecting to your printer, TV and your other computers is another valuable facet of networking. Creating a Network Files System (NFS), which enables you to use the same file system on a variety of appliances, is another very valuable project.

You can use a commercial service like Dropbox or OneDrive. You can store your files on your own computers using ownCloud. Nextcloud is another self hosted productivity platform that keeps you in control of your data.

I like storing my files on a commercial server. Find a company that respects your privacy. Professionally designed and managed file sharing is a valuable service. Keeping your files backed up on a remote commercial server, helps insure that they are not lost in the same fire or flood your computers are lost in.

Git, GitHub and SSH are valuable tools that you should get familiar with. Git is a version control repository that you install on your own computer. It was originally created by Linus Torvalds, the original developer of the Linux kernel. GitHub is a remote file repository, which allows many programmers to login and work on a project. SSH is the secure communications channel you use to connect to GitHub, Bitbucket, SourceForge or any of the other version control repositories.

It seems like there are several programs, like KDE Connect, working on connecting your smart phone to your computer. Joplin is a pretty good note taking app for your phone. Orgzly is a smart phone app that enables you to connect with the Emacs application on your computer.

networkctl

networkctl is part of the systemd-networkd service, which handles network configuration and management in a lightweight and efficient manner. Designed primarily for servers and minimal systems, networkctl offers an alternative to more comprehensive tools like NetworkManager, focusing on simplicity and performance.

By interacting directly with systemd-networkd, networkctl allows users to query the status of network links, bring interfaces up or down and reconfigure them dynamically. It simplifies the process of network troubleshooting and management by presenting clear and concise information about the current state of the system’s network configuration.

The utility operates as a front-end for the systemd-networkd service, which dynamically manages network interfaces based on configuration files. These configuration files, typically stored in /etc/systemd/network/, define how interfaces should behave, including their IP addresses, routes and DNS settings.

When invoked, networkctl communicates with the systemd-networkd daemon to retrieve or modify the state of network interfaces. For instance, running the networkctl list command displays an overview of all detected interfaces, including their operational status, type and configuration setup.

Administrators use networkctl for various tasks such as checking interface statuses or troubleshooting connectivity issues. For example, to examine the details of a specific interface like eth0, the command networkctl status eth0 provides a comprehensive view, including IP addresses, link type and routing information.

In addition to querying statuses, networkctl allows direct manipulation of interfaces. Commands such as networkctl up eth0 and networkctl down eth0 enable users to bring interfaces online or offline as needed. When configuration changes are made, the networkctl reconfigure command applies updates without requiring a full system restart.

One of the most significant benefits of using networkctl is its tight integration with the systemd ecosystem. This integration ensures seamless interaction with other systemd services, such as systemd-resolved for DNS resolution. Lightweight and straightforward, networkctl is particularly suited for headless systems, virtual machines and embedded environments.

The clarity and focus of its output make it an excellent tool for diagnosing network issues. Instead of sifting through verbose logs, administrators can rely on concise summaries provided by networkctl. Its simplicity, however, does not come at the expense of flexibility, as it supports advanced configurations like VLANs, bridges and static routes through properly crafted systemd-networkd files.

Despite its strengths, networkctl is not a full-fledged network manager and lacks a graphical interface, making it less accessible for casual desktop users. Furthermore, managing wireless networks directly requires additional tools like wpa_supplicant, as networkctl does not handle Wi-Fi authentication or scanning.

Another limitation is its reliance on systemd-networkd. Systems using other network management solutions, such as network-manager or legacy ifupdown scripts, will not benefit from networkctl.

networkctl is a powerful and efficient tool for managing network interfaces on Linux systems running systemd-networkd. Its streamlined design, combined with comprehensive capabilities, makes it an excellent choice for administrators who value simplicity and performance. Although it may not cover all use cases, particularly in desktop or Wi-Fi-heavy environments, networkctl excels in server and embedded applications where its lightweight nature and focused functionality shine. Understanding and leveraging networkctl can significantly enhance a system administrator’s ability to manage and troubleshoot network configurations effectively.

Sockets and Ports

Sockets are a software construct, existing solely in the realm of computer programming and networking protocols. They represent a logical endpoint for data transfer between devices, combining an IP address and a port number to uniquely identify a connection.

Sockets are created and managed by the operating system and are used by applications to establish and communicate over network connections. They are not physical entities and do not have a direct hardware counterpart.

Ports can refer to both hardware and software components:

• Hardware ports: Physical interfaces on a device, such as USB ports, Ethernet ports or serial ports, which connect devices to each other or to a network.
• Software ports: Logical ports, which are assigned a unique number (port number) and are used to identify specific network services or applications running on a device.

In the context of computer networking, ports are used to multiplex multiple connections over a single network interface, allowing multiple services to run at the same time. Port numbers are assigned by the operating system and are used to identify processes or services that should receive incoming data.

A socket is an end point of two-way communications, which occurs in a network based on the internet protocol. Sockets will distribute data packets coming through the communication channel to the correct application. It does this using information in the header of the message, such as IP address and port number. Your operating system maps each socket to a process or thread.

There are two types of sockets, called active sockets and passive sockets. An active socket is a socket connected to another active socket, through an open data connection. Active sockets at both ends of the communication channel will be destroyed when the connection is closed.

A passive socket is waiting for an incoming connection. When a passive socket is connected, it will generate a new active socket. An internet socket is identified by the address of the local socket (local IP address and port number), the address of the remote socket and the transport protocol (e.g. TCP, UDP).

Sockets are end points of two-way communications. Ports are logical data connections, which are used to exchange data without using a temporary file or storage. Sockets are associated with a port and there can be multiple active sockets associated with a port. There can also be a single passive socket associated with a port, listening for incoming connections.

Systemd creates and manages the sockets used for communication between system components. For instance, it first creates the socket /dev/log and then starts the syslog daemon. This approach has two advantages: Processes communicating with syslog via /dev/log can be started in parallel. And crashed services can be restarted without losing their connection to processes that communicate with them via sockets. The kernel will buffer the communication while the process restarts.

Ports are network locations implemented in an operating system. They are 16 bit numbers that can be addressed to different services or applications. Ports are identified using the port numbers, the IP address associated with the port and the transportation protocol, such as TCP or UDP.

Ports are always associated with the IP address of a host and the protocol type of the communication. TCP and UDP ports are used to exchange data between computers on the Internet. They are the most widely used ports.

​Ports are specified by a number from 1 to 65535. There are different categories of ports and certain port numbers are reserved for specific types of services.

• 0-1023 – System ports are associated with critical or essential services.
• 1024-49151 – Registered Ports or User Ports can be reserved by sending a request to the Internet Assigned Numbers Authority (IANA).
• 49152-65535 – Dynamic Ports or Private Ports are for private use.

Get your system configured to manage your ports by installing nmap and net-tools. These tools enable you to manage your network using the command line in your terminal. They can reveal a lot about the status of the services running on your machine. systemctl, networkctl and journalctl are commands you can use to program your computer.

To enable or disable a network interface, use the following commands:

sudo networkctl up INTERFACE
sudo networkctl down INTERFACE

To list all network interfaces along with their statuses, use: networkctl
To display detailed information about a specific network interface, use:
networkctl status INTERFACE

To manage the systemd-networkd service, use:

sudo systemctl start systemd-networkd
sudo systemctl enable systemd-networkd
sudo systemctl status systemd-networkd

Services listen on ports by binding to a port/protocol/IP address combination, to wait for requests from clients of the service. When a request is received, the service establishes a one-to-one server client dialog, using the port number.

Open ports can be used to infiltrate your network, so paying attention to which ports on your network are listening is important. Unauthorized open ports can indicate an intrusion.

Understanding Linux ports, and the information being sent in and out of your system through the ports, helps you prevent harmful intrusions. Knowledge about ports is essential for Linux enthusiasts and system administrators. Browse their man pages for more information.

Drivers

Drivers, also known as device drivers, are essential software components that act as intermediaries between a computer’s hardware and its operating system (OS). They enable the OS and applications to interact with hardware devices, ensuring that components like printers, graphics cards and keyboards function as intended. Without drivers, the operating system would not know how to communicate with or control hardware.

A driver is a specialized program that translates high-level instructions from the operating system or applications into low-level commands that hardware can understand. Each hardware device requires a specific driver to operate correctly. For example, a printer driver enables the OS to send print jobs to the printer in a format it can process.

How Drivers Work

Hardware devices have specific communication protocols and registers that define how they operate. Drivers serve as the interface between these hardware protocols and the operating system. When an application sends a command (e.g., “print a document”), the driver translates this into device-specific instructions understood by the hardware. Drivers often interact with the kernel (the core of the operating system) to manage hardware resources like memory, I/O ports and interrupts.

Drivers initialize devices when the system starts or when a device is connected. They also handle ongoing control, such as adjusting display resolution or volume. Drivers facilitate the exchange of data between the hardware and the operating system. For example, a network driver handles the transmission and reception of data packets.

Drivers are categorized based on the type of hardware they manage and their role in the system:

Device Drivers

• Manage specific hardware components.
  • Graphics Drivers: Control GPUs for rendering graphics.
  • Network Drivers: Manage network interface cards (NICs).
  • Printer Drivers: Enable communication with printers.

Kernel Mode vs. User Mode Drivers

• Kernel Mode Drivers:
  • Run in the kernel space with high privileges.
  • Examples: Disk drivers, USB drivers.
• User Mode Drivers:
  • Run in user space with restricted privileges for enhanced security.
  • Examples: Printer drivers, software-based audio drivers.

Virtual Device Drivers

• Simulate hardware devices to allow software to function as if specific hardware were present.
• Example: VirtualBox or VMware drivers for virtual machines.

Bus Drivers

• Manage communication buses that connect multiple devices, such as PCI, USB or I2C.

File System Drivers

• Facilitate access to file systems like NTFS, ext4 or FAT32.

Firmware Drivers

• Act as a bridge between the firmware (embedded in hardware) and the operating system.
• Example: UEFI or BIOS firmware drivers.

Drivers can be installed manually by the user or automatically by the operating system. The process involves identification, where the OS detects the connected hardware and identifies it using unique identifiers like PCI or USB IDs. The OS searches for a compatible driver, either in its preloaded library or online repositories.

The driver software is installed and configuration files are added to the system. The driver is loaded into memory during system startup or when the device is connected.

Common Driver Interfaces

Operating systems provide standardized interfaces to simplify driver development and ensure compatibility. Linux Kernel Modules are Linux drivers implemented as kernel modules, which can be dynamically loaded or unloaded.

Drivers ensure that hardware can communicate with the operating system and applications. Well-designed drivers can improve the performance of hardware, such as achieving faster data transfer speeds or smoother graphics rendering. Drivers unlock the full potential of hardware, providing access to advanced features like GPU acceleration or high-resolution printing. Drivers enforce access controls and ensure secure communication between hardware and software.

Drivers must be compatible with multiple OS versions and architectures. Faulty drivers can cause system crashes or poor performance. Vulnerabilities in drivers can be exploited by attackers to compromise a system. Developing drivers requires in-depth knowledge of hardware and OS internals.

Problems with drivers can manifest as hardware malfunctions or system instability. Common troubleshooting steps include installing the latest version from the manufacturer or OS repository. Revert to a previous version if a new driver causes issues. Use system logs to identify driver-related errors. Remove and reinstall the problematic driver.

Drivers are the unsung heroes of modern computing, enabling seamless interaction between hardware and software. From basic input devices to advanced GPUs, drivers ensure that every component operates efficiently and reliably. As technology evolves, so will drivers, playing a pivotal role in unlocking the full potential of hardware in the digital age. Understanding how drivers work and their importance helps users and developers alike appreciate the complexities of hardware-software integration.