Why cron automates recurring tasks in Linux CLI - Challenge Your Understanding

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why is cron used for recurring tasks?

Which of the following best explains why cron is used to automate recurring tasks on Linux systems?

A Cron is used to manually start tasks on demand.

B Cron executes commands only once when the system boots up.

C Cron runs commands at scheduled times repeatedly without manual intervention.

D Cron requires user input every time it runs a task.

💡 Hint

Think about what 'recurring' means and how cron handles timing.

Cron is a scheduler that runs commands automatically at specified times repeatedly, so users don't have to run them manually each time.

💻 Command Output

intermediate

Output of a cron job listing

What is the output of the command `crontab -l` if the user has these two cron jobs set? 1. Runs a backup script every day at 2 AM 2. Runs a cleanup script every Sunday at 3 AM

Linux CLI

0 2 * * * /home/user/backup.sh
0 3 * * 0 /home/user/cleanup.sh

A

0 2 * * * /home/user/backup.sh
0 3 * * 0 /home/user/cleanup.sh

B

Runs backup.sh at 3 AM every Sunday
Runs cleanup.sh at 2 AM daily

C

backup.sh runs once at 2 AM
cleanup.sh runs once at 3 AM Sunday

D No cron jobs scheduled

💡 Hint

The `crontab -l` command lists the cron jobs exactly as scheduled.

The output shows the exact cron schedule lines for each job, specifying minute, hour, day, month, and weekday.

📝 Syntax

advanced

Identify the correct cron schedule syntax

Which cron schedule line correctly runs a script every 15 minutes?

A * 15 * * * /usr/bin/script.sh

B 15 * * * * /usr/bin/script.sh

C 0 15 * * * /usr/bin/script.sh

D */15 * * * * /usr/bin/script.sh

💡 Hint

Look for the syntax that means 'every 15 minutes' in the minutes field.

The '*/15' in the minutes field means every 15 minutes. Other options run at specific times.

🔧 Debug

advanced

Why does this cron job not run?

A user added this cron job to run a script every day at 1 AM: `0 1 * * * /home/user/myscript.sh` But the script never runs. What is the most likely reason?

A The script does not have execute permission.

B The cron syntax is invalid.

C Cron does not support running scripts at 1 AM.

D The user must reboot the system for cron jobs to start.

💡 Hint

Check if the script can be run manually first.

If the script lacks execute permission, cron cannot run it even if the schedule is correct.

🚀 Application

expert

Determine the number of times a cron job runs in a week

A cron job is scheduled as: `30 6 * * 1-5 /usr/bin/task.sh` How many times will this job run in one week?

A 7 times

B 5 times

C 1 time

D 0 times

💡 Hint

Look at the day-of-week field and count the days it covers.

The job runs at 6:30 AM Monday through Friday, which is 5 days a week.