This question runs the risk of being silly and I think I know the answer, which is "nothing" but I figured I would make extra sure anyway.

I tend to upgrade my servers doing a dist-upgrade and most of the time I ignore the prompt for rebooting (when a kernel gets upgraded). This happens regardless when you have unattended-upgrades on so I don't see this being a problem.

Question is,

What happens if you never reboot after all these upgrades that prompt you for reboot?

Furthermore, what happens if one of these upgrades is a security upgrade? Does that mean the system is insecure until a reboot is performed?


The reboot is required because the kernel been updated with fixes to security issues. The fixed kernel can only be loaded on the next boot, hence the reboot is required. If you don't reboot, your machine will not pick up the kernel security fixes until the next reboot.

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  • So it is impossible to have a secure kernel unless you reboot once a month or so? – Ulukai May 20 '16 at 7:20
  • In practical terms, it is always best policy to ensure that security fixes to the kernel are applied to your machines. One policy is to check the list of fixes in the kernel and see if they are relevant for your use case to deem a reboot is required or not. However, my recommendation is to always ensure you have the latest security fixes applied. – Colin Ian King May 20 '16 at 7:48

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