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control-panels:cpanel-whm:why-cpanel-requests-reboots

Why does cPanel request/recommend reboots?

When running a Linux server there may be periods of time where you require a reboot. These do not typically happen often, but they are required when certain updates occur to the core system files those being systemd related packages and kernel updates(KVM/Dedicated only).

There is software out there that can help prevent this for certain platforms such as Kernelcare(KVM/Dedicated only).

When utilizing cPanel; there are two methods of rebooting within the WHM Interface – Graceful and Forceful Reboot

Graceful Reboot attempts to store user-level processes data prior to ending/terminating their process.

Forceful Reboot will terminate any process and reboot immediately disregarding any potential shutdown errors.

If your server is experiencing high I/O or a high CPU load average then "Graceful Reboot" will potentially hang and cause the server to lock up

In the event you attempt to reboot your server with a Graceful Reboot during high I/O or high CPU usage and it does fail; you can manually issue a reboot to your server via the KnownHost Dashboard within the service manager for your server.

Differences between platforms

There are three different services that we offer that deal with potential reboots. Two types of VPS's and then Dedicated Servers

  • OpenVZ
  • KVM
  • Dedicated

OpenVZ

OpenVZ is containerization based platform. This system shares its kernel with the host-node(Server it resides on). Because of this, these servers don't require kernel updates so when an update does occur; this is typically due to yum repository updates provided by upstream vendors such as CentOS.

These servers won't receive any reboot notification emails. They'll only get the cPanel 'reboot required' message in WHM due to reboots for system related services(such as systemd, dbus, etc).

cPanel does this by polling/querying the 'needs-restarting' command then generates this message in WHM based on its output.

KVM

KVM(Cloud) maintains its own kernel outside of the host node due to using hardware-assisted virtualization. This means that it can require kernel updates in tandem with the yum repository updates by the upstream vendor.

These servers can receive the following notifications from cPanel for rebooting:

The system kernel is at version “3.10.0-957.10.1.el7.x86_64”, but an update is available: 3.10.0-957.12.1.el7.x86_64

Kernel updates can be avoided through services such as Kernelcare which implement 'live-patching' to update the kernel without having to deal with the downtime of a reboot.

This removes the need for rebooting outside of any specific system services.

Dedicated

Dedicated servers are stand-alone physical hardware. These servers like KVM require kernel updates in tandem with the yum repository updates by the upstream vendor.

These servers can receive the following notifications from cPanel for rebooting:

The system kernel is at version “3.10.0-957.10.1.el7.x86_64”, but an update is available: 3.10.0-957.12.1.el7.x86_64

Kernel updates can be avoided through services such as Kernelcare which implement 'live-patching' to update the kernel without having to deal with the downtime of a reboot.

This removes the need for rebooting outside of any specific system services.

How to Reboot through cPanel

cPanel may advise that you reboot anytime that the following occurs;

  • System specific updates (dbus, systemd, etc)
  • Kernel updates (KVM, Dedicated servers only)

When you login through WHM; you may see the following message at the top of your screen.

Your cPanel is showing this message due to pending updates that were updated via nightly cPanel maintenance script but requires a reboot before the new version takes place.

If you're command-line savvy; you can run 'needs-restarting' to see what specifically is calling for a restart.

# needs-restarting
1 : /usr/lib/systemd/systemd --system --deserialize 17 
123 : /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation 

To restart; you can easily click "Reboot now" and the server will perform a Graceful Reboot

Your server should now be rebooting.

If this is a VPS/KVM – it should be back up within minutes, if not less.

If this is a Dedicated Server – it should be back up within 5-10 minutes.

We do recommend that reboots be handled via the KnownHost dashboard for OpenVZ/KVM.

Alternatively; you can issue the 'reboot' command over SSH via your preferred terminal.

control-panels/cpanel-whm/why-cpanel-requests-reboots.txt · Last modified: 2019/05/29 11:23 by Jonathan K. W.