Task configuration command

Use the root crontab (recommended since the target is under /var/log). Create logging/lock dirs, then add the cron entry.

1. Prepare logging/lock directories:

• sudo mkdir -p /var/log/log_archive /var/lock
• sudo chown root:root /var/log/log_archive /var/lock
• sudo chmod 750 /var/log/log_archive

2. Ensure the script is executable:

• sudo chmod +x /opt/ops/log_archive.sh

3. Edit the root crontab:

• sudo crontab -e

Add the following lines (keep them together as a block):

• SHELL=/bin/bash
• PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
• MAILTO=""

• Optional: set timezone for this job (uncomment if needed)

• TZ=UTC

• 5 * * * * /usr/bin/flock -n /var/lock/log_archive.lock -c '/opt/ops/log_archive.sh /var/log/myapp --compress gz --keep 7' >>/var/log/log_archive/log_archive.log 2>&1

Alternative (system-wide /etc/crontab) format if you prefer that file:

• Open with: sudo editor /etc/crontab
• Add:
  • SHELL=/bin/bash
  • PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
  • MAILTO=""
  • 5 * * * * root /usr/bin/flock -n /var/lock/log_archive.lock -c '/opt/ops/log_archive.sh /var/log/myapp --compress gz --keep 7' >>/var/log/log_archive/log_archive.log 2>&1

Time expression explanation

• 5: minute field = at minute 5
• *: hour field = every hour
• *: day of month = every day
• *: month = every month
• *: day of week = every day of week

Overall: runs every hour at HH:05.

Execution environment notes

• User/permissions:
  • Run as root (suggested) so the job can read from /var/log/myapp and write archives/logs without permission issues.
  • Verify ownership/permissions on /var/log/myapp as needed for the chosen user.
• Environment:
  • Cron provides a minimal environment. PATH is explicitly set to include standard system locations.
  • SHELL is set to /bin/bash in case the script relies on bash features.
  • MAILTO is empty to disable cron emails; logs are redirected to /var/log/log_archive/log_archive.log instead.
  • Optional TZ can be set if the schedule must follow a specific timezone different from system time.
• Concurrency protection:
  • flock prevents overlapping runs if one execution takes longer than an hour. The -n option ensures the next run exits immediately if a previous instance is still running.
• Logging:
  • Stdout/stderr are appended to /var/log/log_archive/log_archive.log. Consider configuring logrotate for this file to prevent growth.

Validation steps

1. Manual dry run:

• Execute once manually as root to confirm the script works and has access:
  • sudo /opt/ops/log_archive.sh /var/log/myapp --compress gz --keep 7
• Check exit status (echo $?) and any output.

2. Verify crontab installed:

• sudo crontab -l

3. Check cron service status:

• Debian/Ubuntu: systemctl status cron
• RHEL/CentOS/Alma/Rocky: systemctl status crond

4. Observe next scheduled run:

• Confirm the current time, then wait for the next HH:05 and check:
  • tail -f /var/log/log_archive/log_archive.log
  • On Debian/Ubuntu: grep CRON /var/log/syslog
  • On RHEL/CentOS: sudo tail -f /var/log/cron

5. Test lock behavior (optional):

• While the script is running, try starting another instance:
  • sudo /usr/bin/flock -n /var/lock/log_archive.lock -c '/opt/ops/log_archive.sh /var/log/myapp --compress gz --keep 7'
• It should refuse to start if the lock is held.

Notes

• Absolute paths: The command uses absolute paths to avoid PATH-related failures under cron.
• Exit codes: Ensure /opt/ops/log_archive.sh returns non-zero on failure so issues are visible in logs and monitoring.
• Runtime duration: If the job might exceed 55–60 minutes, keep flock to avoid overlap. Consider performance tuning or spreading workload if needed.
• DST/time changes: “Every hour at minute 5” follows system time. Around DST transitions, it may run 23 or 25 times that day depending on locale.
• Log rotation: Add a logrotate rule (e.g., /etc/logrotate.d/log_archive) for /var/log/log_archive/log_archive.log to prevent unbounded growth.