Re: Query about GRUB comand line functionality

[Bret Busby]

On 26/02/2015, Bret Busby <address@hidden> wrote:
> 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.
>
>
>

Hello.

I have attached a copy of what I believe to be the last usable version
of the grub.cfg file, which I hope will be successfully transmitted as
an attachment.

If not, I will try to send it inline, within a further message.

I have found that file, using the file manager in a Debian 7.60 LXDE
amd64 LiveCD. That does not tell me (that I can interpret), in which
partition, the file sits, due to the use of the meaningless and
obscurantist UUID system of partition descriptors, rather than the
meaningful partition number system ( (hd<x>, gpt<y>) in the PC-BSD
UEFI/GPT system, or /dev/sda<y> in the more meaningful (than UUID)
Debian v <n<=6>  systems)   but, I assume, by context, the following.

The grub.cfg file and the Ubuntu installation, are in partition 12.

The Debian installation is/was in partition 6 (it appears to be not
visible to the Debian 7.6 LiveCD).

Now, the question becomes, given that the now disabled/overridden GRUB
bootloader has apparently been located in the Ubuntu installation in
(apparently) partition 12 of the HDD, how do I disable the BSD
bootloader and re-enable the GRUB bootloader that is apparently in
partition 12 on the HDD?

I understand that a Debian 7.8 installation CD, in the rescue mode,
has the option "Device to use as root file system", which, I assume
would restore the functionality of the GRUB bootloader, if it was in
the Debian installation, but, the last properly functioning GRUB
bootloader is in the Ubuntu installation, and I am not confident that
the Debian software, if used to operate on the Ubuntu system, would
not interfere with the (previous to the sabotage by PC-BSD)
functionality of the Ubuntu installation, and the Ubuntu 14.04 LTS dik
that I have, appears to not have an equivalent of the rescue mode of
the Debian installation CD.

Thank you in  anticipation, for any constructive and helpful advice
that solves the problem.

-- 
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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grub.cfg
Description: Binary data