What is a package manager in Linux?
A package manager is a tool that allows users to install, remove, update configure and manage packages on a Linux operating system. Package managers can be either a command-line tool to graphical user interface application.
What is a package?
A package is compressed archive file that contains all the files for a software application. Packages can be a command-line utility, GUI application or software library.
Packages include:
Pre-compiled binary files.
Installation scripts.
Configuration files.
Dependency requirements etc.
What is systemd?
systemd is a software suite that provides a variety of system components for Linux operating system. It's a collection of programs and libraries, not a single binary.
systemd is a system that is designed specifically for the Linux kernel. It replace the sysvinit process to become the first process with PID=1, which gets executed in user space during the Linux start-up process.
What us systemctl?
systemctl is a command-line tool that manages and monitors the systemd system and service manager in Linux. It's a utility that allows administrators to manage the OS and control the status of services.