Understanding package manager and systemctl
What is a package manager in Linux?
A package manager is software tool that automates the process of installing, updating, configuring, and removing software packages in a Linux system.
A package manager enables users to easily browse, search and install software from a central repository, without having to manually download and install software from the internet.
There are several package manager available in Linux, including apt, dpkg, rvm, yum and pacman, among other. Each package manager has its own commands and package format but they all work to streamline the installation and management of software packages on a Linux system.
package manager also handle dependencies, ensuring that any required libraries or other software components are installed along with requested package. They also provide tools for verifying package integrity, resolving conflicts, and managing updates and upgrades to installed software.
What is a package in linux?
In Linux, a package is a collection of files and software that is bundled together for easy installation and maintenance. Packages typically include the compiled executable files for a program, as well as any necessary configuration files, documentation, and dependencies.
Linux operating systems use package management systems to install, update, and remove software packages. The most common package management systems are:
Using package management systems makes it easy to manage software installations and updates, as well as to ensure that all necessary dependencies are met. Package managers also provide tools for searching and browsing available packages, which can simplify the process of finding and installing new software.
Different kinds of package managers
In Linux, there are primarily two types of package managers:
APT is a command-line tool that downloads packages from software repositories and installs them on the system. It automatically handles dependencies, resolves conflicts, and updates the package database. APT can also be used with graphical user interfaces like Synaptic Package Manager.
RPM is a command-line tool that installs, removes, and queries packages. It can also be used to verify the integrity of installed packages and resolve dependencies. YUM (Yellowdog Updater, Modified) and DNF (Dandified YUM) are package managers that use RPM as the underlying package format.
Other package managers for Linux include:
install docker and jenkins in system by using package managers on Ubuntu and CentOS
steps to install Docker and Jenkins using package managers on Ubuntu and CentOS:
Ubuntu:
Update the package index:
sudo apt-get update
Install Docker:
sudo apt-get install docker.io
Start and enable the Docker service:
sudo systemctl start docker
sudo systemctl enable docker
Install Jenkins:
sudo apt-get install jenkins
Start and enable the Jenkins service:
sudo systemctl start jenkins
sudo systemctl enable jenkins
CentOS:
Install the EPEL repository:
sudo yum install epel-release
Install Docker:
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sudo yum install docker
Start and enable the Docker service:
sudo systemctl start docker
sudo systemctl enable docker
Install Jenkins:
sudo yum install jenkins
Start and enable the Jenkins service:
sudo systemctl start jenkins
sudo systemctl enable jenkins
What is systemctl and systemd
systemctl and systemd are two closely related components in modern Linux distributions.
systemd is a system and service manager that runs as PID 1 and is responsible for managing the system startup process and all system services. It is designed to be compatible with a wide range of Linux distributions, and its main objective is to improve system boot time, manage system services in a unified manner, and provide advanced logging and error tracking capabilities.
systemctl is the primary command-line interface for interacting with systemd. It is used to start, stop, restart, enable or disable system services, among other things.
Here are some of the common systemctl commands:
For example, if you want to start the Apache web server service on a system that uses systemd, you would run the following command:
sudo systemctl start apache2
This command starts the Apache web server service. If you want to make sure that the service starts automatically at system boot time, you would run the following command:
sudo systemctl enable apache2
This command enables the Apache web server service to start automatically at system boot time.
Overall, systemd and systemctl are powerful tools that greatly simplify the management of system services on modern Linux distributions.
systemctl vs service
systemctl and service are two different commands that can be used to manage services on a Linux system, but they operate in slightly different ways.
systemctl is the primary command for controlling the systemd system and service manager, which is the default init system on many modern Linux distributions. It provides a comprehensive set of commands for managing system services, including starting, stopping, enabling, disabling, and querying the status of services.
On the other hand, the service command is a legacy command that is still included on many Linux systems, but is generally not recommended for managing services on modern Linux distributions. The service command works by running scripts located in the /etc/init.d/ directory, which are used to start, stop, and restart services. These scripts are typically not compatible with systemd and may not work correctly on systems that use systemd as their init system.
In general, it is recommended to use systemctl for managing services on modern Linux distributions, as it provides a more comprehensive and consistent set of commands, and is designed to work with systemd-based systems.
Here are some examples of how to use systemctl and service to manage services:
sudo systemctl start apache2
sudo service apache2 start
sudo systemctl stop apache2
sudo service apache2 stop
sudo systemctl enable apache2
sudo chkconfig apache2 on