Introduction of Process

• Process is an instance of program. A new process is started when you gibe any command to Linux machine.
• For a single program, there can be multiple processes.

Types of Processes

Foreground Processes

• Run on the screen
• Input from user is needed
• Example: Office Programs

Background Processes

• Run on background
• Usually, input from user is not needed
• Example: Antivirus

Running a Background Process

• If a program / process is started from terminal, we can’t work on terminal up to the time when program is up and running.
• Data intensive tasks can have lot of processing time which needs a lot of time to be completed. And holding terminal for such long time is not desirable
• Also, if terminal is closed, process along with its child can also be terminated.
• For avoiding this, you need to send the program to background and then only, terminal gets available to you.

How to start Linux Process in Background?

• If process is in executin, press ctrl+z  and enter bg command. This will execute process in background as a job.
• All background jobs can be seen by typing jobs command
• To tun the process on foreground, we use command  “fg”
• Syntax: fg jobname

Some Commands:

• “bg” to esecute process in background
• “fg” to run process on foreground
• “top” tells user about all the running processes
• “ps” command is use to see all the processes running under a user. E.g ps abhash [This is similar to task manager in windows]
• “nice”
  • Nice commands prioritize the process in linux as per your requirements
  • This is niceness in linux , with value in range -20 to 19. Lower the nicensess value, higher the priority of the task.
  • Default value is 0
  • Syntax: nice-n “nice value” process-name
  • Ex: $ nice -9 19 bann
  • If there is process already running, the value can be renice. Syntax: renice “nice value” –p “PID”
• “df” reports free disk space of file sysem
• “free” command shows free and used memory (RAM)