On 07/13/2014 01:01 PM, Timothy Murphy wrote:
> I'm having trouble installing CentOS-7 on my HP MicroServer.
> I've tried with KDE LiveCD and Netinstall (both on USB sticks),
> and now I'm going to try with the DVD ISO.
>
> But I want to be quite sure I can return to CentOS-6.5
> if things go wrong, so I'm wondering what precisely I need to copy
> (eg the MBR and a bit more) so that I could get back to things as they were.
> Is this documented anywhere?
>
> Actually, both failed installations did give a boot menu
> including the old 6.5 system,
> but I'm afraid sometime this might not work,
> and I will be cut off from the world.
>
> Incidentally, the "Repair" option on the netinstall system
> was not as useful as I expected,
> or perhaps I don't know how to use it properly.
> It entered the new CentOS-7 system OK on chroot-ing,
> even mounting other partitions listed in /etc/fstab .
> And I was able to bring up the interfaces with "service network restart".
> But although I ran grub2-install , this did not help matters.
>
> Is there anything else one can do after chrooting into a system?
> Eg, can one boot the system in any way?
>
> Any advice or suggestions gratefully received.
You asked what to keep to be able to boot C6. From your narrative, it
seems that the legacy grub boot for C6 is already gone (blown away) by your
C7 install. I haven't figured out enough about grub2 to be able to tell
you how to preserve your current grub2 configuration, but here are some
possible ways to keep C6 accessible:
1. The Super Grub2 Disk from http://www.supergrubdisk.org seems to be
pretty good at finding any and all possibilities for booting using new and
old versions of grub.
2. If you are reinstalling into exactly the same location as your previous
C7 attempts (same devices for boot and root), just don't let the installer
update the boot information. Since you know it boots both versions now, it
should still boot both versions after the install.
Not knowing what your installation problem is, I can't tell (and you may
not be able to tell either) if anything is wrong with your boot
information, or if that is OK.
3. From C3, install legacy grub onto a USB stick, which would allow you to
boot directly to C6, without any requirement for anything to be on a hard
drive.
4. It is also possible to set up a CD that will boot your computer, but I
don't remember the details of that.
Hope one of these, or something someone else chimes in, will help you.
Also hope you get the C7 install figured out. So far I have only done it
from DVD, and those went well for me.
Ted Miller
Elkhart, IN, USA
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