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I believe GRUB can be told to fallback to a safe mode. I'd assume so; FreeBSD's loader can also do that. The problem was that if a kernel hanged during boot,
by cperciva 9y ago
I believe GRUB can be told to fallback to a safe mode.
I'd assume so; FreeBSD's loader can also do that. The problem was that if a kernel hanged during boot, we wouldn't get back to the loader until someone power cycled the system, so the "try the other kernel" logic wouldn't run.
- srcmap 9y agoThis will be the time where setup HW watch dog should help. After the upgrade, before the reboot, setup the HW watch dog for 2-5 minutes. Setup the boot-old-kernel flags as default in the uboot/EFI/grub/or your system boot loader. If the upgrade the successful (connect to back to the server) and function correctly, disable the "boot-old-kernel" flags in your bootloader. As always, do a lot of testing and automate those tests. You will be surprise how often a simple boot/reset/power cycle can fail if you repeat it over and over again in a weekend.
- cperciva 9y agoHmm, you can set a watchdog before rebooting? I assumed that it would be cleared automatically.