On 07/15/2014 05:22 AM, Timothy Murphy wrote:
> Ted Miller 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?
>
>> 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:
>
> Thanks very much for your comprehensive reply.
>
>> 1. The Super Grub2 Disk from seems to be
>> pretty good at finding any and all possibilities for booting using new and
>> old versions of grub.
>
> I've downloaded this and will try it if necessary.
>
>> 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.
>
> Yes, I'll try that - though I don't remember being asked
> if I wanted to update the bootloader - I probably missed it.
Now that you mention it, I don't remember seeing it in C7 either. Maybe on
the page where you do disk partitioning?
>> 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.
>
> I'm pretty sure it gets through the code in the boot,
> since it says
> [OK] Reached target Initrd Default Target
>
>> 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.
>
> I'm not sure what you mean by C3?
Should have been C6.
> I see that my CentOS-6.5 system has entries in grub/grub.conf
> which don't seem very old (January this year).
>
> I did wonder if one can in fact use grub with CentOS-7,
> since it seems to create an empty (almost) /boot/grub/ folder?
>
>> 4. It is also possible to set up a CD that will boot your computer, but I
>> don't remember the details of that.
>
> Not quite sure what you mean by this?
It is possible to burn a CD with grub or grub2 files on it, which will
allow you to get to one (or both) of your installs. Like a live CD, but
all it does is direct the boot process to your hard disk. (Don't ask me
the details -- did it once with a floppy, but never with a CD).
>> 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.
>
> I've found a second hard disk (from an old server) and put that in,
> so I'll be able to experiment with that,
> without worrying about what it does to my current CentOS-6.5 system.
>
> Also I used to use the old grub interactively -
> I'll see if it is still possible to do this with grub2.
Yes it is, but you have to use the new syntax.
> And I'll try a couple of your suggestions first,
> like not installing the boot-loader.
Hope it works,
Ted Miller
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