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Legal Notice (Imprint)
Information pursuant to § 5 TMG (German Telemedia Act)
Responsible Person
Christian Schulz
Medingstr. 3
29525 Uelzen
Germany
Contact
E-Mail:
Nature of this Website
This is a private, non-commercial project website for the open-source project CronManager, published under the GPL-3.0 License. No commercial activity is conducted through this website.
Disclaimer
Liability for Content
The contents of this website have been created with care. However, we cannot guarantee the accuracy, completeness, or up-to-dateness of the content. As a private service provider, we are responsible for our own content in accordance with § 7 para. 1 TMG. According to §§ 8–10 TMG, we are not obliged to monitor transmitted or stored third-party information or investigate circumstances that indicate illegal activity.
Liability for Links
This website contains links to external third-party websites over whose content we have no influence. Therefore, we cannot accept any liability for this external content. The respective provider or operator is always responsible for the content of linked pages. Linked pages were checked for legal violations at the time of linking; no illegal content was identified. A permanent content check of linked pages is not reasonable without concrete evidence of a violation.
Copyright
Content created by the site operator is subject to German copyright law. The source code of CronManager is published under the GPL-3.0 License on GitHub.
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Open Source Cron Monitoring Tools
If you are looking for an open source cron monitoring tool, the options are limited. Most solutions are either SaaS-based with recurring costs, limited in features, or no longer actively maintained.
Why open source?
Full Data Control
Your execution logs and job configurations stay on your own infrastructure. No data leaves your servers.
No Recurring Costs
No subscription, no per-monitor pricing, no usage limits. Free forever under GPL-3.0.
Flexibility
Modify, extend and integrate as needed. Full source code access on GitHub.
Self-Hosted
Deploy on your own servers. No vendor lock-in, no external dependencies, no account required.
CronManager vs SaaS alternatives
Cronitor, Healthchecks.io
Cloud-based monitoring services. Useful for simple ping-based checks, but require sending data to external servers, charge per monitor at scale, and limit execution log depth on free plans.
CronManager
Self-hosted, open source, actively maintained. Full execution output capture, multi-server monitoring, failure alerts, execution limits and OIDC/SSO — all without a subscription.
CronManager highlights
Execution History & Logs
Full stdout/stderr capture for every run. Timeline charts, swimlane views and KPI cards per job.
Failure Alerts
Email notifications on non-zero exit codes. Configurable per job.
Multi-Host Monitoring
Monitor cron jobs across multiple Linux servers from one dashboard. SSH-based remote execution included.
OIDC / SSO
Integrate with Authentik, Keycloak or any standards-compliant identity provider.
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Cron Job Not Running? Common Causes and Fixes
If your cron job is not running, you are not alone. This is one of the most common issues on Linux systems. Most causes fall into a handful of categories — and all are easy to debug once you know where to look.
Common Causes
Incorrect Cron Syntax
A small mistake in the schedule expression silently prevents execution. Even a missing space or wrong field count will stop a job from running.
Missing Permissions
The script may not have execution permissions, or the cron user may lack access to required files or directories.
Environment Differences
Cron runs with a minimal environment — no $PATH, no aliases, no .bashrc. Commands that work in a shell often fail silently in cron.
Output Not Captured
Cron discards stdout and stderr by default. Without explicit log redirection, errors are completely invisible.
Cron Daemon Not Running
On some systems the cron daemon itself may be stopped or disabled — causing all jobs to silently not execute.
Timezone Issues
Cron uses the system timezone. If your server runs in UTC, schedules may fire at unexpected local times.
How to debug
1. Check if the cron daemon is running
systemctl status cron # Debian/Ubuntu
systemctl status crond # RHEL/CentOS/Fedora2. View recent cron log entries
grep CRON /var/log/syslog | tail -30
# or on systems using journald:
journalctl -u cron --since "1 hour ago"3. Verify your crontab
crontab -l # current user
sudo crontab -l -u root # root crontab
ls /etc/cron.d/ # system-wide entries4. Check script permissions
ls -la /path/to/your/script.sh
chmod +x /path/to/your/script.sh5. Test with cron's limited environment
env -i HOME=/root SHELL=/bin/bash \
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin \
/bin/bash -c 'your-command-here'6. Capture output in your crontab entry
# Append stdout and stderr to a log file:
* * * * * /path/to/script.sh >> /var/log/myjob.log 2>&1Prevent future issues with monitoring
Manual debugging is time-consuming. A cron monitoring tool gives you execution history, output logs and failure alerts automatically — so you know instantly when something goes wrong, without SSH access.
Execution History
Every run recorded with exit code, duration and full output. No more grepping logs manually.
Instant Alerts
Email notification the moment a job fails. Know about issues before they cause problems.
Multi-Server Overview
All your cron jobs across every server in one dashboard. No SSH required to check status.
Start Monitoring Your Cron Jobs
CronManager is free, open source and self-hosted. Deploy in minutes with Docker.
Install with Docker →- Details
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Cron Job Monitoring Tool (Open Source & Self-Hosted)
Cron job monitoring is essential to ensure that scheduled tasks run reliably on your servers. Without monitoring, cron jobs fail silently — leading to broken backups, missed tasks and cascading system issues.
Why cron job monitoring matters
Many systems rely heavily on cron jobs: database backups, automated reports, maintenance scripts, data synchronisation. If any of these fail, the impact is often not noticed immediately — sometimes not until it is too late.
Silent Failures
Cron jobs exit with an error and nobody is informed. No alert, no email — just a missed task.
Distributed Logs
Logs are spread across multiple servers. Correlating failures across systems takes manual effort and SSH access.
No Central Visibility
Without a monitoring tool, there is no way to see at a glance which jobs ran, which failed, and how long they took.
Manual Debugging
Every failure requires investigation. A monitoring tool gives you the execution log immediately — no digging required.
Solution: CronManager
CronManager is a free, open source, self-hosted cron job monitoring tool. Unlike cloud-based services, it runs entirely on your own infrastructure — no subscriptions, no external dependencies, full data ownership.
Execution History with Logs
Every run is recorded — start time, end time, exit code, and full captured output. Available at a click.
Failure Detection & Alerts
Email notification the moment a job exits with a non-zero code. Know about failures before your users do.
Multi-Server Monitoring
Monitor cron jobs across multiple Linux servers from one central dashboard.
Web-Based Dashboard
No SSH required. Manage, debug and analyse all your cron jobs through a modern web interface.
Start Monitoring in Minutes
Deploy CronManager with Docker and start monitoring your cron jobs immediately.
Install with Docker →- Details
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Install CronManager with Docker
The easiest and fastest way to get started. Deploy CronManager with Docker Compose using pre-built images from Docker Hub — no PHP required on the host.
Deploy in 3 Minutes
curl -fsSL https://raw.githubusercontent.com/csoscd/cronmanager/main/docker/docker-compose-full.yml -o docker-compose.yml
docker compose up -dOn first visit, a setup wizard guides you through creating the initial admin account.
What you get
Fully Containerised
Web UI and agent both run as Docker containers. No PHP installation on the host required.
Ready in Minutes
Download the example Compose file, adjust the .env section, and start. The setup wizard handles the rest.
Easy Updates
docker compose pull && docker compose up -d — that is all it takes to update to the latest version.
Requirements
Prerequisites
Docker Engine 20.10+ and Docker Compose v2. Any Linux distribution. No PHP required on the host.
Prefer a host-based agent? See Agent on Host installation →