Run a program forever in linux

Running programs indefinitely ensures that services and applications are always available, reliable, and capable of handling real-time data and tasks effectively. So People often want to run programs indefinitely on computers.

In Linux, if you have root access, you can use systemctl to manage services and ensure that they run continuously. Without root access, you can use pm2, a process manager for Node.js applications, to keep programs running. Here’s how you can use both methods:
Using systemctl (with root access)
Create a service file:
Create a new service file in /etc/systemd/system/, for example, myprogram.service.

   [Unit]
   Description=My Program
   After=network.target
   [Service]
   ExecStart=/path/to/your/program
   Restart=always
   User=your-username
   WorkingDirectory=/path/to/working-directory
   [Install]
   WantedBy=multi-user.target

Reload the systemd daemon:

   sudo systemctl daemon-reload

control the service:

   sudo systemctl start|stop|restart|status myprogram.service

Enable the service to start on boot:

   sudo systemctl enable myprogram.service

Using pm2 (without root access)
Install pm2:
If pm2 is not already installed, you can install it using npm:

   npm install pm2 -g

Start your program with pm2:

   pm2 start /path/to/your/program --name myprogram

Ensure pm2 restarts your program on system reboot:

  pm2 save
  pm2 resurrect  //create a cron job @reboot

Both tools ensure that your program runs continuously and can be set to start automatically on system boot.

here’s a table comparing systemctl and pm2:

Feature	systemctl	pm2
Access Level	Requires root access	Does not require root access
Installation	Built-in on most Linux distributions	Requires installation via npm
Service Management	System-level service management	User-level process management
Configuration	Service files in /etc/systemd/system/	Managed through pm2 CLI
Startup Script Creation	Manual setup in service file	pm2 startup command
Process Monitoring	Systemd handles restarts and monitoring	pm2 handles restarts and monitoring
Automatic Restart on Failure	Yes	Yes
Logs Management	Journald (using journalctl to view logs)	Built-in logging and monitoring (pm2 logs)
Run at Boot	systemctl enable	pm2 save + pm2 startup
Multi-user Support	Yes	Yes
Ease of Use	Requires knowledge of systemd units	Simple and intuitive CLI
Application Type	Any (general-purpose)	Mainly for Node.js apps but supports others
Web Interface	No	Yes (pm2-gui for a web dashboard)
Community and Documentation	Extensive documentation	Extensive documentation and active community
Additional Features	Timers, targets, and dependencies support	Load balancing, clustering, and more