[Bug 1652332] Re: Alternative to BIOS-Boot partition

2017-09-20 Thread Colin Watson
It seems wrong to me that the system has neither an EFI System Partition
nor a BIOS Boot Partition, certainly, but it could well have been the
result of manual partitioning, in which case it wouldn't be a bug: the
installer does not guarantee to protect the user from all possible
misconfigurations.  That's why we need installer logs as I mentioned in
my previous comment: they should make it possible to determine how the
system ended up that way.

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Title:
  Alternative to BIOS-Boot partition

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[Bug 1652332] Re: Alternative to BIOS-Boot partition

2017-09-20 Thread Bougron
Sorry for having provided you the entire boot-info report from a windows
XP.

I just extracted the part that surprises me.
The question is simple:
Is it a good installation?
Is this a bug from the installer?
If Yes, will it be corrected?.

** Attachment added: "contents of MBR of GPT device"
   
https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1652332/+attachment/4953410/+files/boot2.txt

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Title:
  Alternative to BIOS-Boot partition

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[Bug 1652332] Re: Alternative to BIOS-Boot partition

2017-09-19 Thread Colin Watson
I don't think I understand what you're objecting to.  Is the problem
that the installer failed to set up the correct partitioning structure?
If so, we'd need installer logs (/var/log/installer/syslog and
/var/log/installer/partman).  If the problem is something else, please
explain what's going on in plain language rather than continuing to
throw large attachments at us.

(It would generally be appreciated if you could attach text files
separately as plain text and where necessary explain what they relate
to, rather than pasting them all into a large LibreOffice document.)

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Title:
  Alternative to BIOS-Boot partition

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[Bug 1652332] Re: Alternative to BIOS-Boot partition

2017-09-19 Thread Bougron
Thank you very much for your detailed explanations.
So I think there is a huge malfunction in the ubuntu installation software 
version 16.04. and perhaps the following ones because in version 1404 this was 
not possible.
Is it possible to confirm and to raise the problem.

** Attachment added: "Boot1.doc"
   
https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1652332/+attachment/4953088/+files/Boot1.doc

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  Alternative to BIOS-Boot partition

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[Bug 1652332] Re: Alternative to BIOS-Boot partition

2017-09-19 Thread Colin Watson
In your original report, you said "in the root partition".  The
technique we use on MBR disks is to write the GRUB core image *outside*
any partition, in the area before the first partition sometimes called
the "boot track" or the "embedding area".  This is at least safe against
being rearranged by file system implementations, as I noted above.

But having the boot loader's code outside any partition has its
problems.  It means that the space in question isn't clearly allocated
for use by the boot loader, so it's possible for it to be capriciously
overwritten by something else that decides to make use of an unallocated
area of disk.  (Such software in fact exists, and has resulted in quite
a few very strange bug reports.  GRUB has to take some quite exotic
defensive measures against it.)  The reason that we don't normally use a
partition on MBR disks despite this problem is that the MBR format has
rather restrictive rules for partitions, especially if you're trying to
install the OS on a system that already has some other OS installed, and
it works out better to avoid using a whole partition just for the boot
loader.

GPT has much more sensible partitioning rules, and it's straightforward
to just use a partition there.  This gets us the best of both worlds: we
don't have to worry about our bits being overwritten by other software
(malicious or otherwise - I've seen both) that writes into the area
before the first partition, and we don't have to worry about them being
moved around by a file system implementation because that partition is
just raw and doesn't contain a file system.  In a way it is a bit like
the behaviour you observe on MBR disks, except it's better: rather than
hoping that nobody else will write into the same area of disk, we
require that it be made it clear in the partition table which area of
disk we're using.

So it is true that it would be technically possible to return GPT disks
to the prior practice from MBR disks of not bothering to indicate in the
partition table what area of disk we're using and just picking an area
that's unlikely to be used by anything else; but it would be a step
backwards, and so we won't do that.

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  Alternative to BIOS-Boot partition

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[Bug 1652332] Re: Alternative to BIOS-Boot partition

2017-09-19 Thread Bougron
I remember that with MS-DOS device you write the beginning of the boot
from sector 1 to sector 2047.

Why, it is not possible to write the same thing from sector 256 to
sector 2047  when the device is GPT except if this sequence is too big?.

But if this sequence is   realy too big,  one day, it will be the same
thing for MS-DOS device...

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Title:
  Alternative to BIOS-Boot partition

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[Bug 1652332] Re: Alternative to BIOS-Boot partition

2017-09-19 Thread Bougron
Helleo
Thanks for yor anwser and remark. But i thinks that ubuntu 16.04 use already 
this technic.

** Attachment added: "Legacy boot on GPT deice without partition boot"
   
https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1652332/+attachment/4952805/+files/boot.doc

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  Alternative to BIOS-Boot partition

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[Bug 1652332] Re: Alternative to BIOS-Boot partition

2017-09-18 Thread Colin Watson
Thanks for the suggestion.  However, we very deliberately don't do it
the way you suggest, because it would mean the boot loader would too
easily be broken by perfectly legitimate internal rearrangements
performed by the file system.  For example, a file system might quite
reasonably move the physical locations of files during fsck, and we
don't want that kind of thing to require updating the parts of the boot
loader in the MBR.  A dedicated partition is much more robust.

** Project changed: ubiquity => ubiquity (Ubuntu)

** Changed in: ubiquity (Ubuntu)
   Status: New => Won't Fix

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  Alternative to BIOS-Boot partition

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