GNU bug report logs - #33389
parted not recognizing partitions in "non-standard" MBRs with valid partition tables

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Marc Stenson <marcstenson <at> gmail.com>
Subject: bug#33389: closed (26.1.90; Emacs occasionally fails to receive
 asynchronous subprocess output in batch mode)
Date: Thu, 27 Dec 2018 20:59:02 +0000

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Your bug report

#33389: parted not recognizing partitions in "non-standard" MBRs with valid partition tables

which was filed against the parted package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 33389 <at> debbugs.gnu.org.

-- 
33389: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=33389
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Philipp <p.stephani2 <at> gmail.com>
Cc: 33389-done <at> debbugs.gnu.org
Subject: 26.1.90; Emacs occasionally fails to receive asynchronous subprocess
 output in batch mode
Date: Thu, 27 Dec 2018 12:58:30 -0800

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> I don't think the manual states that output can
> arrive after the process has finished, but if that's the case, then it
> should do so.

Good point, and I installed the attached patch into emacs-26 to try to do that.

As this bug report seems to stem from a misunderstanding of 
accept-process-output (quite understandable, as its functionality is obscure) 
I'm taking the liberty of closing the report. If I'm wrong please feel free to 
reopen it.

[0001-Improve-accept-process-process-doc.patch (text/x-patch, attachment)]

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From: Marc Stenson <marcstenson <at> gmail.com>
To: bug-parted <at> gnu.org
Subject: parted not recognizing partitions in "non-standard" MBRs with valid
 partition tables
Date: Thu, 15 Nov 2018 00:27:02 +0200

Hello,

While parted 2.3 had no issues with whatever was in the first 446 bytes 
of the MBR and only looked at the partition table, newer versions such 
as 3.2 seem to be thrown by unusual boot code (e.g. Grub4DOS) and either 
show the entire disk as unallocated space or as one big volume/partition 
with the file system of the first volume. This is despite the partition 
table being fully compliant and happily read by fdisk and sfdisk.

This may be a "feature" rather than a bug.   Please pardon my ignorance, 
perhaps newer partition table schemes require the first 446 bits to be 
parsed.  However it could save someone many hours of frustration if this 
was noted prominently in the documentation.

In my case It was fixed with a simple:
  dd if=/usr/lib/syslinux/mbr/mbr.bin of=/dev/sdb bs=446 count=1
after taking the requisite backups and a deep breath.

Thanks and regards,
Marc

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