[CentOS] Upgrading (?) from legacy boot to UEFI

Sat Aug 28 09:58:00 UTC 2021
Rob Kampen <rkampen at kampensonline.com>

On 28/08/21 8:24 pm, Simon Matter wrote:
>> On 27/08/21 10:51 pm, Rob Kampen wrote:
>>> Unfortunately the server is remote and the CentOS7 USB device I left
>>> plugged into the machine refuses to boot from UEFI mode. Thus a rescue
>>> mode boot has not been possible.
>> So i made a trip and replaced the USB stick with another one - CentOS7
>>> I am unsure what file I need to point the UEFI bios disk manager setup
>>> at, I have tried shim.efi and shimx84-centos.efi
>>> The message I get is that linux16 and initrd16 cannot find their
>>> files. The change to linuxefi and initrdefi also fail but the system
>>> reboot happens before I can see what flashes on screen.
>>> Is a USB based UEFI booted rescue mode the only way I can fix this?
>> So I then rebooted - selected UEFI native boot and got into rescue mode
>> - only problem is that the rescue system did not find a Linux system.
>> Really weird as each of the four drives effectively have a complete
>> centos7 system. No idea why it didn't start md raid and find the 6 raid1
>> volumes.
>> About to give this a miss and just live with legacy boot - this UEFI
>> thing is just far too complicated. Looking on line at all the various
>> blogs and questions it seems I am not alone in finding it far too
>> complicated.
> Don't worry, you're not alone. IMHO UEFI and GRUB2 and the whole Linux
> startup procedure can be a real problem to handle and I guess most people
> just give up earlier or later and simply use the installer to do the job.

Yeah, it is astounding to me that RH does not define their 
implementation of the grub2 grub.cfg file with particular focus on the 
things that are different between legacy boot and UEFI. Also what (if 
any) differences there may be in the initramfs and vmlinuz files between 
the two boot options. then we have the various .efi files with little or 
no documentation. So we are left with anaconda ....

Makes my situation really tough ... too small for the learning curve of 
automated OS installation and management systems but I have a week or so 
of configuration and testing invested that I will need to redo, if I do 
a re-install just to get the boot system shifted from BIOS/legacy to UEFI.

As to the RH decision to default to a legacy boot / MBR oriented install 
based upon size of disk ... words fail me.

At least I have learnt that one needs to do research into MB firmware 
w.r.t BIOS/UEFI as part of procurement. Never been a thing I cared about 
previously, but now another area which can bite you in the butt.

> Simon
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