A couple of afterthoughts on this (after starting to work on the bug).

The CentOS system is actually 6.7, not 6.2 as I'd thought. It has been
upgraded fairly regularly over the years.

The kernel isn't vanilla 2.6 - it contains a vast number of patches
retrofitted by Red Hat (the version number is 2.6.32-696.16.1).



On Sun, 2022-02-13 at 22:56 +0000, Peter Duffy wrote:
> Hi Emanuel
>
> Thanks for that link. It's OK - I'm not hosting websites on my CentOS 6
> box! There are a number of reasons why I've been terrified of trying to
> upgrade this box up to now - and the experience of the last fortnight
> has tended to confirm most of my existing fears and add a few more
> besides. I'm just glad that I decided to take a clone of the hard disk
> before starting the upgrade.
>
> If the grub guys have just arbitrarily decided not to support kernel v2,
> then it was probably a bit high-handed of them. Red
> Hat/CentOS/Scientific Linux/Oracle version 6 was the last version before
> systemd'struction, and I suspect that there may be quite a lot of boxes
> around still running it.
>
>
> On Sun, 2022-02-13 at 23:09 +0100, Emanuel Loos via Dng wrote:
> > Hello Peter,
> >
> > looks like someone else is experiencing the same issue (though there
> > where no answers yet):
> >
> > https://www.linuxquestions.org/questions/linux-kernel-70/gnu-grub-version-2-04-you-need-to-load-the-kernel-first-4175707760/
> >
> > I don't see version 2 of the Linux kernel listed on https://kernel.org/
> > so if you are hosting websites there how is this secure? If you want a
> > stable kernel, how about a longterm version? How about configuring and
> > compiling it yourself so it matches your needs best?
> >
> > By the way: They are GNU/Linux or GNU+Linux distributions, Devuan calls
> > itself a GNU+Linux distribution, Debbian calls itself a GNU/Linux
> > distribution. They are all based on the GNU operating system with the
> > Linux kernel.
> >
> > The GNU Project, developing an operating system that's completely free
> > software (as in freedom, not free beer), was the start of the free
> > software movement, long before Open Source existed, but it doesn't get
> > acknowledged that much since companies are okay with the idea of Open
> > Source (viewing releasing the source code as a good idea sometimes,
> > because it is more profitable), but really don't like the idea of free
> > software (viewing the freedom of computer users as a must and not
> > granting the four essential freedoms of free software when releasing
> > software as something unethical which does harm to society).
> >
> > Kind Regards
> >
> > Emanuel Loos
> >
> > On 2/13/22 10:05 PM, Peter Duffy wrote:
> > > I've got an old box running CentOS 6.2 and Windows 7. Without going into
> > > details, this box is vital and I use it every day. Finally I decided
> > > that I had to bite the bullet and upgrade the linux system, and I
> > > decided to go for chimaera.
> > >
> > > Built a new box from scratch and cloned all the disks, using dd, to
> > > fresh HDDs (there are several big data disks in the box). Made another
> > > clone of the first disk just for safety's sake, then installed chimaera
> > > on free space on the first disk - successful; chimaera and windows 7
> > > both booted fine. But CentOS 6.2 wouldn't boot - sometimes automatic
> > > reboot, sometimes blank screen and hung box.
> > >
> > > Switched back to the latest clone disk, which fortunately booted
> > > successfully, made a fresh clone of the working disk, then tried again:
> > > this time, installed beowulf. Install was successful - and this time
> > > devuan, windows 7 and CentOS 6.2 all booted successfully.
> > >
> > > Took another safety clone of the first disk (I'm beginning to wonder if
> > > I've exhausted the world's stock of 2T HDDs) and then upgraded beowulf
> > > to chimaera. Upgrade successful. Again, the CentOS 6.2 system wouldn't
> > > boot.
> > >
> > > CentOS 6.2 uses kernel 2.6 - it's possible to upgrade to a later one,
> > > but this is frowned upon. I suppose it's based on RedHat and
> > > derivatives' policy of setting a base version per distro and then
> > > retrofitting updates. (I did once try upgrading to a v4 kernel, and the
> > > system became completely unstable.)
> > >
> > > Removed the primary disk, put in the clone with beowulf installed, and
> > > verified that all was still working. Then put the disk with chimaera in
> > > another box with identical hardware, and started digging into the
> > > problem. Grub on chimaera = 2.04-20; on beowulf = 2.02+dfsg1-20
> > > +deb10u4. Booted into chimaera and downloaded the packages for the
> > > beowulf grub release (grub2, grub2-common, grub-common, grub-pc, and
> > > grub-pc-bin), and used them to downgrade grub on the chimaera system -
> > > successful. Rebooted - CentOS 6.2 now boots. Tried going into the grub
> > > command line environment on each box, and using the "linux" command to
> > > load the 2.6 kernel image: result was in grub 2.02, it works fine, and
> > > in 2.04, the box reboots at that point.
> > >
> > > So current conclusion is that something has happened between grub 2.02
> > > and 2.04 which prevents the latter from loading linux v2 kernels. The
> > > challenge now is to find out what, and if it's possible to work around
> > > it in grub 2.04. (I should say that I originally assumed that the
> > > problem was down to moving a disk (or a clone of it) from a non-UEFI
> > > environment to a UEFI one - but setting everything in the firmware to
> > > "legacy only" didn't have any effect.)
> > >
> > > Just wondered if anyone had any thoughts and comments (other than why
> > > the hell am I still running CentOS 6.2 on this box), before I start
> > > rummaging through the grub changelogs. Apologies for the length of this
> > > and also if I've missed something obvious. The above is a heavily
> > > boiled-down summary of about a fortnight of stress and lost sleep.
> > >
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