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Re: Automatic Boot Disk redirector?

Cross-posted to 2 groups.

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In comp.sys.ibm.pc.hardware.storage Paul <nospam@needed.com> wrote:
> R. C. White wrote:
>> Hi, Yousuf.
>> 
>>>  Well, as I said, I removed all of the partitions previously marked as 
>>> "active", and it made no difference.
>> 
>> Well, as I said, ONE partition on the boot device MUST be "active".  
>> That's the partition that will act as the "System Partition" - and that 
>> "System" label will appear in Disk Management's Status column for that 
>> partition.
>> 

> This is true in Windows perhaps, but there are other OSes out there.
> The boot flag 0x80 is a "suggested serving". The MBR code can look at
> it, or ignore it. Windows OSes happen to like it.

Actually, Windows is stupid here. Any sane OS loader will be
flexible and just require a partition to be specified to it.
Windows relies on the hostoreic mechanism of the "active" flag.

Despite what some here have said, an arbitrary
number of partitions can be active at the same time. This
is not magic, just one byte in the partirion descriptor
that is 0x80 if active and 0x00 otherwise.

> I didn't know about this, until one day I had an OS
> disk with a Linux distro on it, and no boot flag. Unlike these guys,
> I didn't even know there were install options for grub. Grub is a
> big mystery to me, and having a grub and grub2 (two streams) doesn't help.

Grub-legacy is a finished product. Grub2 is a major redesign and 
under development, but already usable. Chose either as to your needs.

> http://www.linuxquestions.org/questions/debian-26/what-is-this-bootable-flag-562885/

>    "If you installed grub to MBR, it will boot with or without bootflag"

> Virtually every time I install a grub, I get a surprise. For example,
> I thought grub stage 1.5 was stored in sectors below 63, and just two
> days ago, found a virtually completely clean first 63 sectors, with
> no hint of grub at all. 

Stage 1.5 is where you put it, i.e. typically in a file. The 
difference is that stage 1 loads it by knowing its block
numbers on the device, while stage 1.5 does understand filesystems
and loads stage 2 via filesystem addressing. All in the documentation 
here:

http://www.gnu.org/software/grub/manual/legacy/grub.html#Images

> Just too many variables, for me to keep track of.

Then you better not mess with booting. Sorry, not everything is easy.

Arno
-- 
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno@wagner.name
GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
----
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans

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Thread

Automatic Boot Disk redirector? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-16 08:11 -0500
  Re: Automatic Boot Disk redirector? Arno <me@privacy.net> - 2012-01-16 13:40 +0000
    Re: Automatic Boot Disk redirector? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-16 09:56 -0500
      Re: Automatic Boot Disk redirector? "R. C. White" <rc@grandecom.net> - 2012-01-16 13:20 -0600
        Re: Automatic Boot Disk redirector? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-17 06:27 +1100
        Re: Automatic Boot Disk redirector? Arno <me@privacy.net> - 2012-01-17 01:30 +0000
        Re: Automatic Boot Disk redirector? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-17 03:44 -0500
          Re: Automatic Boot Disk redirector? Paul <nospam@needed.com> - 2012-01-17 04:20 -0500
          Re: Automatic Boot Disk redirector? "R. C. White" <rc@grandecom.net> - 2012-01-17 11:53 -0600
            Re: Automatic Boot Disk redirector? Paul <nospam@needed.com> - 2012-01-17 15:42 -0500
              Re: Automatic Boot Disk redirector? Arno <me@privacy.net> - 2012-01-17 21:07 +0000
                Re: Automatic Boot Disk redirector? Paul <nospam@needed.com> - 2012-01-17 19:23 -0500
              Re: Automatic Boot Disk redirector? "R. C. White" <rc@grandecom.net> - 2012-01-17 20:23 -0600
                Re: Automatic Boot Disk redirector? Arno <me@privacy.net> - 2012-01-18 03:22 +0000
                Re: Automatic Boot Disk redirector? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-18 16:05 -0500
            Re: Automatic Boot Disk redirector? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-18 15:50 -0500
              Re: Automatic Boot Disk redirector? Wolf K <wekirch@sympatico.ca> - 2012-01-18 16:55 -0500
                Re: Automatic Boot Disk redirector? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-18 19:30 -0500
          Re: Automatic Boot Disk redirector? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-18 07:04 +1100
      Re: Automatic Boot Disk redirector? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-17 06:24 +1100
      Re: Automatic Boot Disk redirector? Arno <me@privacy.net> - 2012-01-17 01:29 +0000
  Re: Automatic Boot Disk redirector? Paul <nospam@needed.com> - 2012-01-16 12:58 -0500
    Re: Automatic Boot Disk redirector? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-17 03:48 -0500

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