Cron jobs for scheduled tasks in Raspberry Pi - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a cron job?

A cron job is a scheduled task that runs automatically at set times or intervals on a Raspberry Pi or other Linux systems.

beginner

How do you edit the cron jobs for the current user?

You use the command crontab -e to open the cron table editor for the current user.

intermediate

What does the cron time format look like?

It has five fields: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-7, Sunday=0 or 7). Each field controls when the task runs.

intermediate

How would you schedule a script to run every day at 7:30 AM?

You write this in crontab: 30 7 * * * /path/to/script.sh. This means at minute 30, hour 7, every day, every month, every day of the week.

intermediate

Why is it important to use full paths in cron jobs?

Because cron runs with a limited environment, using full paths ensures the system finds the commands and scripts correctly.

Which command opens the cron editor for the current user?

A cronedit

B editcron

C cron -open

D crontab -e

The command crontab -e opens the cron table editor for the current user.

In a cron schedule, what does the '*' symbol mean?

A Skip this field

B Every possible value for that field

C Only once

D No value

The '*' means the task runs for every possible value in that time field.

How often will this cron job run? 0 0 * * 0 /home/pi/script.sh

A Every Sunday at midnight

B Every day at midnight

C Every hour on Sunday

D Every minute on Sunday

The '0' in the day of week field means Sunday, so it runs at 00:00 every Sunday.

Why should you use full paths in cron commands?

A Because cron has a limited environment and may not find commands without full paths

B To make the command shorter

C To make the command run faster

D It is not necessary to use full paths

Cron runs with a minimal environment, so full paths ensure commands are found and run correctly.

What does the following cron time mean? */15 * * * *

A Every 15 days

B Every 15 hours

C Every 15 minutes

D Every 15 seconds

The '*/15' in the minute field means every 15 minutes.

Explain how to create a cron job that runs a backup script every day at 2 AM on a Raspberry Pi.

Think about the time fields and how to edit the cron table.

Describe why cron jobs might fail if you do not use full paths or environment variables.

Consider what environment cron runs in compared to your normal terminal.