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Re: Query about command line commands

From: Bret Busby
Subject: Re: Query about command line commands
Date: Mon, 9 Mar 2015 17:01:25 +0800

On 09/03/2015, Andrei Borzenkov <address@hidden> wrote:
> В Mon, 9 Mar 2015 16:17:16 +0800
> Bret Busby <address@hidden> пишет:
>> Hello.
>> On a problem system, I have "GNU GRUB version 2.02~beta2"
>> as shown in the command line window.
>> The system is a UEFI/GPT system.
>> Three or four operating systems are apparently more or less installed
>> on the system, and the installation attempt of the last operating
>> system, broke everything.
>> I have found that I am able, at the GRUB command line, to run ls,
>> which returns a list of the partiitions (hd0,gpt<x for x= 1 to 13>).
>> I can also run ls (hd0,gpt<x>), which returns a description of the
>> partition filesystem.
>> I can also run ls (hd0,gpt<x>)/ , which lists the top level contents
>> of the partition.
>> Now, my query is this; with the command set that is available at that
>> level, can I mount a USB thumb drive (eg, mount <device descriptor>
>> <mount device name> (I do not know whether that would the the order of
>> the syntactical components, or, what would be the correct syntax),
> grub does not "mount" anything. It enumerates devices using firmware
> interfaces (BIOS or EFI) and provides you with names. So to access USB
> stick you would need to plug it before booting and it will be available
> in grub as hdX (note that exact number depends on order in which EFI
> probes for them).
>> and, direct a copy of each command and return output, to a file on the
>> USB drive, eg, where I have
> No. GRUB does not support writing to a filesystem. Nor do I quite
> understand what you are trying to do here and how would it help you.

I figured that if I would be able to do what I want, with ouputting
the information to a USB drive file, I would be able to show what is
in each partition, so as to be able to select the appropriate one(s)
for restoration of the system, to an operable computer system with
which I could select which operating system I want to boot.

Whilst the last operating system that was attempted to be installed,
PC-BSD, is an operating system that I now consider too dangerous to
try again, due to the damage that it has done, and, therefore, I do
not want to be able to boot that operating system, the computer has
had (and apparently, still has) an installation of MS Windows 8, then
it had Debian 7 installed, thence the MS Win8 installation could not
be found, and then it had Ubuntu 14.04 LTS installed, and, the Ubuntu
installation, with its acompanying GRUB, found Ubuntu and Debian, and,
I was thence able to boot into either Ubuntu of Debian (but, not MS
Windows), and, when PC-BSD was kind of installed, it buried everything
else on the system, and, is inoperable, leaving me with a mostly
inoperable computer. About the only thinbg that now works on the
computer, is the GRUB 2.02 beta2 command line interface, with which I
am mostly unfamiliar, beyond getting the ls command to work, as much
as I have been able to get it to work.

I have ,managed to find what I believe to be the Ubuntu 14.04
installation partition, with its grub.cfg file, but, the Debian LiveCD
could not find anything that resembled the Debian 7 installation
partition. When I tried to install the PC-BSD, it was to a partition
that was not the Debian partition, so it should have not deleted the
Debian installation (but, with what it has done, that would not
surprise me).

I believe that, with the action that I wanted to perform, in writing
the list of the contents of each partition, to external media, such as
a USB thumbdrive, I could then find which operating system, is
installed where, and, what to do to recover the system, instead of
having to trash the system.

I believe that, from memory, I found a partition, using the GRUB ls
command, that may have been the Debian installation partition, but, in
the absence of being able to write the output of the commands, to
external media, it is like doing an archaeological dig under a flowing
river - the stuff that is found, my be washed away, when a person
returns to try to find it again.

But, you say that that method is not available, so I have to either
find another way to restore the system to at least the state that it
was, before PC-BSD sabotaged it, if not also, getting MS Windows to be
able to be selected to boot, in addition to the installed Debian and
Ubuntu, or, to trash the system and built it again from scratch,
without any prospect of having MS Windows able to boot, as Mcrosoft
stopped providing installable media, years ago.

> If you are using EFI system, bootloaders are installed in ESP (EFI
> System Partition) which is likely what you listed below
>> ls (hd0,gpt2)/
>> efi/
>> ls (hd0,gpt2)/efi/
>> Microsoft/ Boot/ oem/
>> ....
>> "
> And firmware keeps list of boot entries that refer to file on ESP. So
> usually to fix booting on EFI it is enough to fix firmware list of boot
> entries or simply set default boot entry. But if your output above is
> correct, you do not have any boot entries at all (besides Microsoft).
> Dud you install your Linux systems in EFI or BIOS mode?


Bret Busby
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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