Debug School

rakesh kumar
rakesh kumar

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Server Reboot Explained: What, Why, When, and How to Restart Safely

Rebooting means restarting a computer or server. It shuts down the running system and starts it again.

For a server, rebooting can activate updates, reset running processes, and help check whether websites and services recover automatically.

1. What Is a Server Reboot?

  • A reboot restarts the entire server.
  • Running applications and services stop.
  • The operating system starts again.
  • Services configured to start automatically come back online.
  • Websites may be unavailable briefly during this process.

Simple example: Think of rebooting as turning your phone off and back on.

2. Why Should You Reboot a Server?

Activate Kernel Updates

  • The kernel is the core of the operating system.
  • It manages memory, hardware, and running programs.
  • A new kernel can be installed while the old one is still running.
  • A reboot normally loads the new kernel.

Example from our server:

  • Before reboot: 6.8.0-1063
  • After reboot: 6.8.0-1066

The newer kernel had already been installed. Restarting allowed the server to use it.

Load Updated Libraries

  • Applications use shared libraries to perform common tasks.
  • Examples include OpenSSL and glibc.
  • Running applications may keep using old library versions after an update.
  • Restarting affected services or rebooting helps load the updated versions.

Release Memory

  • Stopping processes releases the memory they were using.
  • A reboot can temporarily help when a program leaks memory.
  • If the problem returns, investigate the application.

Remember: A reboot may relieve a problem without fixing its cause.

Reset Stuck Processes

  • Some services may become unresponsive.
  • Restarting the affected service is often enough.
  • A full reboot may help when the problem affects the whole system.

Check Automatic Startup

  • A planned reboot tests whether important services start by themselves.
  • This includes web servers, databases, and background workers.
  • Missing startup configuration can leave websites offline.

In our case, LAMPP did not start automatically after rebooting, so the websites remained unavailable for approximately eight hours.

3. When Should You Reboot?

Reboot when:

  1. Ubuntu reports that a restart is required.
  2. A newly installed kernel needs to become active.
  3. A system update specifically requires a reboot.
  4. Planned maintenance requires restarting the machine.
  5. A system-wide problem cannot be resolved by restarting the affected service.

There is no fixed rule that every server must reboot weekly. Follow update requirements and operational needs.

4. What Is the Difference Between Rebooting and Restarting LAMPP?

Action What restarts? Typical impact
Restart LAMPP Services managed by LAMPP Websites and database connections may be interrupted
Reboot the server The entire operating system and all processes Every application on the server is interrupted

Restart LAMPP:

sudo /opt/lampp/lampp restart
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Reboot the server:

sudo reboot
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Restarting LAMPP does not activate a newly installed kernel.

5. How Do You Check Whether a Reboot Is Needed?

Check Ubuntu’s reboot notification:

cat /var/run/reboot-required
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Example output:

*** System restart required ***
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Check which packages requested the reboot:

cat /var/run/reboot-required.pkgs
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If these files do not exist, Ubuntu has not recorded a reboot requirement through this mechanism.

Check the currently running kernel:

uname -r
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Check how long the server has been running:

uptime
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6. What Should You Check Before Rebooting?

  1. Choose a quiet time.

    Reboot when fewer people are using your websites.

  2. Check important jobs.

    Avoid interrupting backups, deployments, imports, or other critical tasks.

  3. Confirm automatic startup.

    Make sure required services are configured to start after boot.

  4. Check your recovery access.

    Ensure you can use the hosting provider’s console if SSH does not return.

  5. Confirm backups are available.

    Keep recent backups as part of normal server maintenance.

  6. Inform affected users if needed.

    Let them know about the planned maintenance window.

7. What Should You Check After Rebooting?

  1. Reconnect through SSH.
  2. Check the active kernel: 
uname -r
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  1. Check uptime: 
uptime
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  1. Check LAMPP: 
sudo /opt/lampp/lampp status
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  1. Open every important website.
  2. Test login and database-dependent pages.
  3. Check background workers and scheduled tasks.
  4. Review errors if anything fails to start.

If LAMPP is stopped, start it:

sudo /opt/lampp/lampp start
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Starting it manually restores its services, but automatic startup still needs to be configured separately.

8. Who Should Perform the Reboot?

  • A server administrator or an authorized team member.
  • Someone who can check the websites afterward.
  • Someone who has access to troubleshoot startup failures.

For a production server, the person performing the reboot should remain available until the essential services are working.

9. Which Problems Does a Reboot Not Fix?

A reboot does not permanently fix:

  • Bugs in application code.
  • Slow database queries.
  • Incorrect configuration.
  • Insufficient server capacity.
  • A full disk.
  • A compromised server.
  • Missing automatic startup settings.

These problems need separate investigation and corrective action.

10. Will Rebooting Delete Website Data?

  • A normal reboot does not delete saved website files or database records.
  • Unsaved work and data held only in memory can be lost.
  • Active requests, uploads, and connections may be interrupted.
  • Temporary-file cleanup depends on system configuration.

11. How Much Downtime Will a Reboot Cause?

Downtime depends on:

  • Server boot speed.
  • Update or filesystem checks.
  • Database startup time.
  • Automatic service startup.
  • Application readiness.

Do not assume a fixed duration. Measure your server’s actual recovery time during planned maintenance.

12. What Did We Learn From Our Server?

  1. The reboot activated the newer kernel.
  2. Installing an update and running that update are different things.
  3. The operating system restarted successfully.
  4. LAMPP did not start automatically.
  5. Website checks after reboot would have revealed the problem sooner.

The main lesson: Plan the reboot, configure automatic startup, and verify that your websites are working afterward.

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