Cron log monitoring in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Identify the cron job execution from log output

Given the following snippet from a cron log, what command was executed by cron?

Linux CLI

Jun 10 14:05:01 server CRON[12345]: (root) CMD (/usr/bin/backup.sh)

A /usr/bin/update.sh

B /usr/bin/cleanup.sh

C /usr/bin/restart.sh

D /usr/bin/backup.sh

💡 Hint

Look for the CMD part in the log line.

The cron log line shows the command executed after CMD. Here it is /usr/bin/backup.sh.

❓ Troubleshoot

intermediate

Diagnose why a cron job did not run

You see no output or log entries for a cron job scheduled at 3 AM daily. Which of these is the most likely reason?

A The system time is set correctly

B The cron daemon is not running

C The cron job script has execute permission

D The cron job is listed in crontab -l

💡 Hint

If cron daemon is stopped, no jobs run or log.

If the cron daemon is not running, no cron jobs will execute or produce logs.

❓ Configuration

advanced

Configure cron to log all job outputs to a specific file

Which crontab entry correctly redirects both stdout and stderr of /usr/bin/script.sh to /var/log/script.log?

A 0 2 * * * /usr/bin/script.sh > /var/log/script.log 2>&1

B 0 2 * * * /usr/bin/script.sh 2> /var/log/script.log

C 0 2 * * * /usr/bin/script.sh > /var/log/script.log

D 0 2 * * * /usr/bin/script.sh 2>&1 > /var/log/script.log

💡 Hint

Redirect stdout first, then stderr to the same file.

The correct syntax redirects stdout to the file, then redirects stderr (2) to where stdout (1) points.

✅ Best Practice

advanced

Best practice for monitoring cron job failures

Which method is best to get notified immediately when a cron job fails?

A Check cron logs manually every day

B Write output to a local file only

C Configure cron to send email on job failure

D Ignore failures if jobs run mostly fine

💡 Hint

Immediate notification helps quick response.

Configuring cron to send emails on failure alerts you immediately to fix issues.

🧠 Conceptual

expert

Understanding cron log rotation impact

If cron logs are rotated daily and compressed, what is a key consideration for long-term cron job monitoring?

A Archived logs must be decompressed to analyze older cron jobs

B Cron jobs stop running after log rotation

C Cron daemon automatically deletes old logs without compression

D Log rotation disables cron logging temporarily

💡 Hint

Compressed logs need special handling to read.

Rotated logs are compressed files; to review older cron logs, you must decompress them first.