What is the difference between starting a service and enabling a service?
Starting a service and enabling a service are two distinct actions in the realm of Linux system administration, specifically in the context of service management with systemd. While they both involve managing services, they serve different purposes and have different implications.
Starting a service refers to the action of initiating the execution of a particular service on a Linux system. This action can be performed manually by a system administrator or automatically during system boot. When a service is started, it begins running and performs its designated tasks or provides the functionality it is designed for. Starting a service typically involves executing a command that triggers the service to launch and become active.
On the other hand, enabling a service involves configuring the system to automatically start the service during the system boot process. Enabling a service ensures that it starts automatically whenever the system is powered on or restarted. This configuration is achieved by creating a symbolic link from the service's unit file to the appropriate location in the systemd hierarchy. Enabling a service does not immediately start it; rather, it sets up the conditions for the service to start automatically when the system boots up.
To illustrate the difference between starting and enabling a service, let's consider the example of the Apache HTTP Server. If the Apache service is already installed on a Linux system, starting the service would involve executing a command like `sudo systemctl start apache2`. This command would initiate the Apache service, and it would become active and start serving web pages.
However, if the system administrator wants the Apache service to start automatically every time the system boots up, they would need to enable the service using a command like `sudo systemctl enable apache2`. This action would create the necessary symbolic links in the systemd hierarchy, ensuring that the Apache service is automatically started during system boot.
Starting a service is the action of manually or automatically initiating the execution of a service, while enabling a service involves configuring the system to automatically start the service during system boot. Both actions are important in managing services on a Linux system and serve different purposes in ensuring the availability and functionality of the desired services.
Other recent questions and answers regarding Advanced sysadmin in Linux:
- Apart from the mentioned commands, what other options and functionalities does the journalctl command offer? How can you access the manual page for journalctl?
- What is the role of the systemd journal in storing logs in Linux systems?
- What are the advantages and disadvantages of using the journalctl command to access logs compared to traditional plain text log files?
- What is the significance of the "-fu" flag in the "journalctl -fu [unit]" command? How does it help in real-time log monitoring?
- What is the purpose of the "journalctl -u [unit]" command in Linux system administration? How does it differ from the default "journalctl" command?
- Why is it important to run the cleanup commands with sudo privileges?
- What command can you use to restrict the cleanup of logs based on their size using the systemd journalctl tool?
- How can you specify the time measure when using the "–vacuum-time" option with the journalctl command?
- What command can you use to delete logs older than a certain time period using the systemd journalctl tool?
- How can you check the size of the systemd journal on a Linux system?
View more questions and answers in Advanced sysadmin in Linux