Job Scheduling In Linux

at command→ at command can be used to schedule a job to run at a specific time.

STEPS TO SCHEDULE JOB

1. We need to install at first

   sudo apt-get install at

2. Once it is installed, We must start and enable it.

   sudo systemctl start atd

   sudo systemctl enable atd

3. To schedule the creation of an empty file, use the at command.

   for example: To create a file 1 min from now

   echo “touch/path/to/yourfile.txt” | at now +1 minute

   Check the file has been created

   ls

Limitation of at command → We can’t use it to run recurring tasks.

CRONTAB

A crontab (short for cron table) is a configuration file in Unix-like systems used to schedule and automate tasks (jobs) to run at specified times or intervals. It’s managed by the cron daemon, a background service that executes the scheduled tasks. Each line in the crontab defines a task and the time when it should run, following a specific syntax.

Cron Daemon

The cron daemon is a background service in Unix-like operating systems that executes scheduled tasks at specified times. It continuously runs in the background, checking the crontab files for any jobs that need to be executed at the current time.

Crontab Syntax:

_ _ _ _ _ command

| | | | |—>Day of the week (0-7) (Sunday to Saturday)

| | | |———>Month (1-12)

| | |—————>Day of the month (1-31)

| |———————>Hour(0-23)

|—————————>Minute(0-59)

Example: 20 1 * * 2 /path/to/script.sh

This will run script located at /path/to/script.sh every Tuesday at 1:20 am.

crontab demo:

1. open crontab file by using command crontab -e

2. choose the editor , as per your need

3. * * * * * touch /home/ubuntu/file This command will run every minute of every hour of everyday of every month and everyday of the week to create the file.

4. The file created should be visible in home directory, check if the file has been created.

Linux Crontab is a powerful utility that is used for Scheduling and Automating Tasks in Unix-like operating systems. It facilitates the users to run the scripts or Linux Commands at specified times and intervals.