CentOS

rsync is a program that can be used to synchronize files and directories across a variety of local and remote locations. It can interact with multiple operating systems, work over SSH, provide incremental backups, execute commands on a remote machine, and replace the need for the cp and scp commands. The rsync program is an invaluable asset for any system administrator who intends to run a server or manage a network of computers, as it not only simplifies the process of making backups in general, but it can be used to action a complete backup solution.

In this process, we will investigate the role of server automation and the convenience of running specific tasks at predefined periods by introducing you to the time-based job scheduler known as cron. Cron allows for the automation of tasks by enabling the administrator to determine a predefined schedule based on any hour, any day, or any month. It is a standard component of the CentOS operating system, and it is the purpose of this process to introduce you to the concept of managing recurring tasks in order to take advantage of this invaluable tool and to make CentOS work for you.

In this process, we will learn how to manage your system’s users and groups on CentOS 7. Essential user and group managing skills are one of the most important CentOS system administrator fundamentals.

To Start With: What Do You Need?

To complete this process, you will need a working installation of the CentOS 7 operating system with root privileges and a console-based text editor of your choice.

The Process

This process shows you how to manage users and groups by learning how to add, delete, and modify them:

Journald’s advantages over other logging systems such as rsyslog is that it is very efficient and logs just about everything on your system automatically without the need to configure anything because it is a part of the systemd suite. The main disadvantage is that all journald log information will get lost after a system’s restart. Journald logging can produce huge amounts of data and by default, all logging information is only kept in memory, which is not very practicable if you need to access older log information or analyze causes of system crash reboots.

Log files contain system messages and output from services, the kernel, and all kinds of running applications. They can be very useful in many situations, for instance, to troubleshoot system problems and monitor services or other system resources, or doing security forensics after a breach of security. In this process, you will learn the basics of how to work with logging services using journald.

Often, a big part of every system administrator’s work is troubleshooting the server when something goes wrong. This is especially true for your system’s services, as they are constantly running and processing information all the time. Services can be dependent on other services and on the server’s system, and there will be situations in your administrator’s life where the system services will fail or refuse to start. Here, in this process, we will show you how to troubleshoot them if something goes wrong.

Linux system services are one of the most fundamental concepts of every Linux server. They are programs which run continuously in your system, waiting for external events to process something or do it all the time. Normally, when working with your server, a system user will not notice the existence of such a running service because it is running as a background process and is therefore not visible. There are many services running all the time on any Linux server. These can be a web server, database, FTP, SSH or printing, DHCP, or LDAP server to name a few.

The Linux kernel is a program that constitutes the central core of the operating system. It can directly access the underlying hardware and make it available to the user to work with it using the shell.

In this process, we will learn how to prime the kernel by working with dynamically loaded kernel modules. Kernel modules are device driver files (or filesystem driver files) that add support for specific pieces of hardware so that we can access them.

In this process, we will learn how to display a welcome message if a user successfully logs in to our CentOS 7 system using SSH or console, or opens a new terminal window in a graphical window manager. This is often used to show the user informative messages, or for legal reasons.

To Start With: What Do You Need?

To complete this process, you will require a minimal installation of the CentOS 7 operating system with root privileges and a console-based text editor of your choice.

In this process, we will learn how to provide nominated users or groups with the ability to execute a variety of commands with elevated privileges.