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Old 09-27-2011, 07:31 PM
PM
 
Default A basic question regarding grub display options

To boot to recovery, you can amend the linux line of the entry

from

linux /boot/vmlinuz-x.x.x-xx-generic root=UUID=xxxxxxx ro splash quiet

to

linux /boot/vmlinuz-x.x.x-xx-generic root=UUID=xxxxxxx ro 1

But making this change, would permanently do what? Means I would be able to hide that option? or what?

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Old 09-27-2011, 07:33 PM
PM
 
Default A basic question regarding grub display options

This command notifies the memory manager that specified regions of RAM ought to be filtered out (usually, because they're damaged). This remains in effect after a payload kernel has been loaded by GRUB, as long as the loaded kernel obtains its memory map from GRUB. Kernels that support this include Linux, GNU Mach, the kernel of FreeBSD and Multiboot kernels in general.




Syntax is the same as provided by the Memtest86+ utility: a list of address/mask pairs. Given a page-aligned address and a base address / mask pair, if all the bits of the page-aligned address that are enabled by the mask match with the base address, it means this page is to be filtered. This syntax makes it easy to represent patterns that are often result of memory damage, due to physical distribution of memory cells.


I didn't know about it but it seems useful. I would not remove it rather leave it in the system. But wanted to know only, would play how it looks if hidden?

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Old 09-27-2011, 07:33 PM
Colin Law
 
Default A basic question regarding grub display options

On 27 September 2011 18:20, Goh Lip <g.lip@gmx.com> wrote:
> On Wed, 28 Sep 2011 00:47:10 +0800, Colin Law <clanlaw@googlemail.com>
> wrote:
>
>> If you ever had problems that prevented a normal boot then it is
>> easier to recover if this option is still in you boot options. *With
>> linux you can do anything you like, so it is up to you to decide
>> whether to take the risk.
>
> To boot to recovery, you can amend the linux line of the entry
> from
> linux /boot/vmlinuz-x.x.x-xx-generic root=UUID=xxxxxxx ro splash quiet
> to
> linux /boot/vmlinuz-x.x.x-xx-generic root=UUID=xxxxxxx ro 1

I was not suggesting that it is not possible to boot into recovery
after removing it from the boot list, merely that it is easier if it
is still there. The question for the OP is whether the benefit of
removing it (whatever that benefit is) outweighs the risk of having to
use the above technique - if he can remember it, and if he knows how
to get to the point of editing the entry.

Colin (Law, not Watson)

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Old 09-27-2011, 07:34 PM
Goh Lip
 
Default A basic question regarding grub display options

On 28/09/11 03:31, PM wrote:


To boot to recovery, you can amend the linux line of the entry
from
linux /boot/vmlinuz-x.x.x-xx-generic root=UUID=xxxxxxx ro splash quiet
to
linux /boot/vmlinuz-x.x.x-xx-generic root=UUID=xxxxxxx ro 1


But making this change, would permanently do what? Means I would be able
to hide that option? or what?



This means it is safe to disable the recovery portion because if you
really need it, it can still be assessed by the above modifications.


Regards - Goh Lip


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Old 09-27-2011, 07:37 PM
PM
 
Default A basic question regarding grub display options

This means it is safe to disable the recovery portion because if you really need it, it can still be assessed by the above modifications.


Okay, that what I wanted to know in simple words. Thx.

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Old 09-27-2011, 07:40 PM
Goh Lip
 
Default A basic question regarding grub display options

On 28/09/11 03:33, Colin Law wrote:

I was not suggesting that it is not possible to boot into recovery
after removing it from the boot list, merely that it is easier if it
is still there. The question for the OP is whether the benefit of
removing it (whatever that benefit is) outweighs the risk of having to
use the above technique - if he can remember it, and if he knows how
to get to the point of editing the entry.

Colin (Law, not Watson)


Yes, I understand what you mean perfectly. Actually I agree with you.
I'll leave all these alone. But PM asked a valid question and we did
answer him technically well. (which may not be 'practically' well)


Regards - Goh Lip

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Old 09-27-2011, 07:41 PM
PM
 
Default A basic question regarding grub display options

On 28/09/11 02:49, NoOp wrote:


But the question still remains re memtest86: "Rather than remove it, why

not remove the executable bit?" as suggested on the

https://help.ubuntu.com/community/Grub2 *page?

...




We'll have to leave it to Colin to answer that; personally I'll won't remove anything as the facility 'badram' may come useful however unlikely. I referred to the section on badram and to quote from the website or the info facility (both are the same)......looks 'generously useful'.




Regards - Goh Lip
In my opinion, Colin Watson just answered my questions explicitly, like how these could be done. But as a novice, I didn't know those all details that those packages are useful (and that's why Ubuntu provides them in the initial boot itself!!) but this fact ('that I am new') was not know to him (Mr.Colin Watson), so might have answered explicitly but anticipated some elucidations which I got! Thx to everyone.



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Old 09-27-2011, 07:46 PM
PM
 
Default A basic question regarding grub display options

I was not suggesting that it is not possible to boot into recovery

after removing it from the boot list, merely that it is easier if it

is still there. *The question for the OP is whether the benefit of

removing it (whatever that benefit is) outweighs the risk of having to

use the above technique - if he can remember it, and if he knows how

to get to the point of editing the entry.



Colin (Law, not Watson)
Thx Colin for that modification, it seems useful, I would try that but wanted to know in only simple line like Goh Lip did, I understood with a sentence that ' This means it is safe to disable the recovery portion because if you
really need it, it can still be assessed by the above modifications' rather than reading this para, that's only!

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Old 09-27-2011, 07:56 PM
Goh Lip
 
Default A basic question regarding grub display options

On 28/09/11 03:46, PM wrote:



I was not suggesting that it is not possible to boot into recovery
after removing it from the boot list, merely that it is easier if it
is still there. The question for the OP is whether the benefit of
removing it (whatever that benefit is) outweighs the risk of
having to
use the above technique - if he can remember it, and if he knows how
to get to the point of editing the entry.

Colin (Law, not Watson)


Thx Colin for that modification, it seems useful, I would try that but
wanted to know in only simple line like Goh Lip did, I understood with a
sentence that ' This means it is safe to disable the recovery portion
because if you really need it, it can still be assessed by the above
modifications' rather than reading this para, that's only!




PM, Colin Law's is very valid and is much 'wiser' than from just a
purely technical point of view. When reading his post, I think I should
have adopted his reply instead of mine, an inhuman mechanical response,
correct but useless.


Take care - Goh Lip


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Old 09-27-2011, 10:10 PM
NoOp
 
Default A basic question regarding grub display options

On 09/27/2011 12:28 PM, PM wrote:
>> Rather than remove it, why not remove the executable bit?
>> https://help.ubuntu.com/community/Grub2
>> [/etc/grub.d/ (directory)]
>> <quote>
>> 20_memtest86+ Searches for /boot/memtest86+.bin and includes it as an
>> option on the GRUB 2 boot menu. There is currently no line option to
>> remove this entry from the menu. The display of memtest86+ can be
>> inhibited by removing the executable bit from this file and running sudo
>> update-grub.
>> </quote>
>>
>
> Removing only the executable bit makes recovery mode still in the system but
> that option would not be highlighted in the display. Is it like that? It's a
> better option then.

That does indeed work for me; all of my systems have the excutable bit
removed. You can test for yourself; open a terminal and enter (without
the '$' - that's the prompt):

$ sudo chmod 644 /etc/grub.d/20_memtest86+

Then reboot and you should no longer see it on the grub menu. To change
it back should you need/want to in the future:

$ sudo chmod 755 /etc/grub.d/20_memtest86+



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