Re: Query about GRUB comand line functionality

[Bret Busby]

On 25/02/2015, Simon Hobson <address@hidden> wrote:
> Bret Busby <address@hidden> wrote:
>
>> The system is completely broken, due to attempting to install an extra
>> operating system, which now appears to me, to be a trojan horse.
>>
>> The system previously had installed, MS Windows 8 (which got lost,
>> when Debian Linux was installed, but, the loss of MS Windows 8, on
>> that computer, has not been a problem, for me), Debian Linux 7.x and
>> Ubuntu Linux 14.04 LTS.
>>
>> That is the order in which the operating systems were installed,
>> before the additional one broke the system.
>>
>> When Debian Linux was added, GRUB showed only the Debian Linux OS.
>>
>> When Ubuntu Linux was added, the Ubuntu GRUB showed the boot options
>> of Ubuntu and Debian.
>>
>> When the trojan horse operating system was added, the bootloader shows
>> only the trojan horse operating system, which does not boot.
>>
>> In trying to restore the system to the state before the trojan horse
>> operating system, I have found how to get to a GRUB command line
>> prompt, which shows above specified version of GRUB as being present.
>
> Often the easiest way to fix things is to boot a live CD/USB drive close to
> one of the installed OSs and work from there. I know some of the Debian
> installers (everything but the "Net install ?) have an option for rescue and
> live modes. In Rescue mode, you can specify a partition to mount as your
> root volume, and from there you have a working system that you can use to
> repair the rest.
>
> What I'd do is :
>
> Boot from a Live CD/USB drive.
> Mount each partition one at a time and have a look at what it contains - a
> listing of the partitions will also tell you what type it is, if Win8 is
> still there then that should show as NTFS. If there's a /etc/fstab then
> that's a Linux/Unix root filesystem and you can see from the contents of the
> file what other partitions it uses. You can also look for files like
> /etc/debian_version which will give you a bit more clue as to which is
> which.
>
> Once you have identified a suitable root partition, use rescue mode to start
> the system and mount that as the root filesystem - actually I think it does
> a chroot. You can mount it's other filesystems (mount -a) and then have a
> booted system. From there, you can use update-grub and grub-install to put a
> working bootloader back in place.
> Whether grub shows all the other systems depends on the settings you give
> it, and/or what the distro configures it to do. From memory, I think Debian
> defaults to looking for others.
>
> The tricky thing with multiple OSs is managing the bootloader. By default,
> each one will want to install it's own. So whenever you do anything in
> Ubuntu that needs an update to the boot config, it'll do it's own thing and
> install the grub that's installed in Ubuntu. Similarly for Debian. And of
> course, Windows will just blow away anything it feels like !
>
> So it may be best to remove (uninstall & purge) the grub package(s) from all
> but one OS. You then have to reboot into that one OS whenever your need to
> update grub - but you'll have a more consistent experience.
>
> The tricky one is that many installers will want to install their own by
> default - and it may or may not be difficult to persuade them not to screw
> up your current install. From memory, Debian does ask before installing
> grub, and it asks if you want to scan for other OSs. I have a feeling that
> some others, especially in "easy install" mode, may just go ahead and do
> what they like.
>
>
> PS - what was the last OS you installed that broke it ?
>

Answer to the "PS" - PC-BSD 10.1.1 - it was supposed to be able to
allow PC-BSD to be installed into a selectable OS booting UEFI/GPT
computer system, using the GRUB bootloader, as the selectable OS
bootloader (I use the term "selectable OS booting", rather than
"multi-booting", as, to me, multi-booting means being able to boot
multiple operating systems, concurrently, which, I believe, instead,
requires virtual machines, like VMWare), and, allowing the person
performing the installation, to select into which GPT partition,
PC-BSD would be installed, but, instead, it has wrecked the computer
system, rendering the system unusable without either restoring GRUB,
if that can successfully be done (which appears increasingly
doubtful), or, a complete system rebuild, involving re-installing each
of the operating systems that was previously installed (which excludes
MSWin8, as no installation media, were provided with the computer).
PC-BSD 10.1.1 is dangerous, and, to me, a trojan horse thing.

I had gone into the rescue mode, using a Debian 7.8 install iso image,
and got to a screen that said something like "Into which of the
following partitions do you want to install the root partition?", and
it listed the 13 GPT partitions, in the format of something like
/dev/sda<x> .

But, it did not show which were the OS partitions (one for each of
MSWin8, Debian 7, and Ubuntu 14.04 LTS).

In trying to use the GRUb command line to which I had referred, I
hoped to try to find which of the partitions were the OS partitions,
so as to hopefully be able to restore the GRUB bootlaoder, and be able
to boot one of the bootable operating systems.

In trying to find whether I could save the sequence of command line
commands and the respective response outputs, I had hoped to be able
to, using a USB thumbdrive, examine the information on a usable
computer, and figure out what to do next.

At present, I do not know which partitions are the appropriate
partitions into which to install root systems, so I am unable to use
the rescue mode -> restore grub process.

It took me about an hour, to get the system to provide me with the
information for me to (and, including my doing it, to)  write down the
information that I believe to be the relevant information from the
GRUB
> ls (hd0, gpt<x>)
commands for each of the partitions.

Then, the next day that I have the time to do it, I expect that it
will take me another hour or two, to obtain and write down the
information from the GRUB
> ls (hd0, gpt<x>)/
commands for each of the partitions, to try to establish what is each partition.

It may be another week, before I can allocate that time

The GRUB ls commands appear to not show partition labels for the non
PC-BSD OS partitions, even though they should have labels (unless the
OS partition labels have been stripped by the PC-BSD installation
procedure, in addition to the other damage that it has done to the
system),

>From a response that I have seen on another mailing list, to my query,
the GRUB command line does not provide for mounting a USB thumb drive,
then writing all commands and responses, from a start point to an end
point, to a file to be saved on the USB thumb drive, then to unmount
the USB thumbdrive, which would otherwise allow the commands and
responses, to be examined as wanted, on an operable system, without
having to boot the now inoperable system, into the GRUB command line
mode (which appears to be all that works, now, on that computer), to
rerun the commands, each time that I want to re-examine the commands
and the responses.

That is unfortunate, as the functionality that I want, would be quite
helpful, if it would be available.


-- 
Bret Busby
Armadale
West Australia
..............

"So once you do know what the question actually is,
 you'll know what the answer means."
- Deep Thought,
 Chapter 28 of Book 1 of
 "The Hitchhiker's Guide to the Galaxy:
 A Trilogy In Four Parts",
 written by Douglas Adams,
 published by Pan Books, 1992

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