If you run automated security updates on Ubuntu then you should know there is following gotcha with grub update:

When our instance automatically updated these packages: grub-common grub-pc grub-pc-bin grub2-common it caused start of os-prober which blocked main filesystem with attempts to “recognize filesystem and OS”. And this attempts crashed several running cronjob tasks. It all happened during the night so our “happiness” in the morning was incredible…

 

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