Thanks for that approach.  As I can get to USB drives, would the 
following work as root:

1.  Insert a blank multi byte external USB drive (e.g., Western Digital, 
other vendors) on another machine and leave a blank format

2.  Assuming that the drive on the failed machine is /dev/sda (e.g., 
sda1 ... sdaN), and that the external drive appears as /dev/sdb,
issue

dd if=/dev/sda of=/dev/sdb

thereby "imaging" the current harddrive but having exact images of 
/home, /opt, and the like

3.  Install SL7.5 from the bootable USB iso install image, manually 
partitioning to same sizes as on the existing drive

4.  cp -pr /home and the like from the USB image drive to the "new" SL 
7.5 system, thereby restoring all files

Note that the above has far fewer manual steps than the suggested procedure.

I often use yumex GUI to perform such updates.  If the network 
"glitches"  during a yumex massive update, would the system again be in 
an unbootable state?

Does anyone have a mechanism for SL7.5 to perform an upgrade rather than 
a new install booting from the install ISO image file?

Thanks,

Yasha Karant

On 08/21/2018 03:47 PM, Nico Kadel-Garcia wrote:
> On Tue, Aug 21, 2018 at 5:53 PM Yasha Karant <[log in to unmask]> wrote:
>> During the upgrade of a SL 7 non-current system to SL 7 (via yum update
>> as root from the Internet), the campus network "glitched" and the system
>> hung.  The 7.5 partially installed system panics; it has not recovered.
>> The 7 non-current will boot but no X (no GUI), only a scrolling text
>> terminal, presumably from which yum can be executed.
> If you want to keep this beastie alive, I urge you to:
>
> * Boot from a live USB or DVD image with networking enabled
> * Mount the old partitions at /mnt/sysimage, with subpartitions
> appropriately under that
> * chroot to /mnt/sysimage
> * Run "rpm --rebuilddb", because it is probably corrupt
> * Get the list of installed packages with "rpm -qa --qf '%{name}.%{arch}\n'"
> * For every package, use "yum upgrade $name" and "yum reinstall $name"
> * * yum reinstall may require enabling the obsolete repositories
> * One or more are likely to balk due to two distinct versions of the
> same package.  Resolve that balking package manually, downloading the
> current version and using "rpm -U --replacepkgs $name"
>
>> I have downloaded Scientific-7.5-Install-Dual-Layer-DVD-x86_64.iso and
>> then put this onto an USB flash "thumb" drive that I have confirmed is
>> bootable and will start the installation steps.  I do not want to do a
>> new install but rather an upgrade, not touching /home , /opt and the like.
>>
>> I have found old upstream vendor instructions for a previous upstream
>> vendor major release of the enterprise (not enthusiast) system; please
>> see below.  How are these to
>> be modified for SL 7.5?  If I boot the Install ISO image (from the USB
>> drive), is there a way to get to the old GUI upgrade option that seems
>> no longer available?
> It's nearly impossible to tell which components got messed up in a
> mass upgrade. Start from a cleaned up upgrade process, as described
> above.
>
>> Please reply to [log in to unmask]  Any assistance would be appreciated.
>>
>> Yasha Karant