DaemonForums  

Go Back   DaemonForums > OpenBSD > OpenBSD General

OpenBSD General Other questions regarding OpenBSD which do not fit in any of the categories below.

Reply
 
Thread Tools Display Modes
  #1   (View Single Post)  
Old 30th March 2016
geek geek is offline
New User
 
Join Date: Oct 2015
Posts: 6
Default Partitioning schemes

What is the situation with partitioning in OpenBSD now? At least formerly, I think, OpenBSD required non-OpenBSD MBR partitions to be described in the OpenBSD MBR partition's disklabel, which I think is complete madness and an example of bad design. In my opinion, sub-partitioning schemes should not refer to data outside of the subdivided MBR partition, and they should not use absolute disk addresses. They should use offsets relative to the subdivided partition's address.

https://web.archive.org/web/20151121...foreignfsafter

And what is the situation with OpenBSD's GPT support? Does OpenBSD still require disklabels or can it use GPT partitions directly? Can OpenBSD 5.9 use MBR partitions without having them described in a disklabel?
Reply With Quote
  #2   (View Single Post)  
Old 30th March 2016
jggimi's Avatar
jggimi jggimi is offline
More noise than signal
 
Join Date: May 2008
Location: USA
Posts: 5,746
Default

Quote:
Originally Posted by geek View Post
...OpenBSD required non-OpenBSD MBR partitions to be described in the OpenBSD MBR partition's disklabel...
There has been no change to the process. A recognized foreign filesystem that is described in an MBR or GPT partition table will be assigned a virtual disklabel partition letter, beginning with "i", if there is no OpenBSD disklabel already on the drive. Once an OpenBSD disklabel is written to a drive, foreign filesystems in an MBR or GPT partition table are ignored.
Quote:
...which I think is complete madness and an example of bad design... In my opinion, sub-partitioning schemes should not refer to data outside of the subdivided MBR partition, and they should not use absolute disk addresses. They should use offsets relative to the subdivided partition's address.
Alternative solutions will be given review and consideration by the Project if they arrive as proposed source code changes to the tech@ mailing list. Culturally, the developers will ignore suggestions -- no matter how valid -- if they arrive as prose to that list or other mailing lists, which is the way to reach Project members. Active members here at this forum are just users, we don't drive this particular bus..

The reason for this attitude? OpenBSD considers itself a research project, with developments driven by the wants and needs of its developers/researchers, not by the desires of any users of the software who come along for the ride.
Quote:
And what is the situation with OpenBSD's GPT support? Does OpenBSD still require disklabels or can it use GPT partitions directly?
OpenBSD 5.9, just released, supports UEFI boot and/or GPT partitions. But the use of foreign file systems is as described above.
Reply With Quote
  #3   (View Single Post)  
Old 30th March 2016
geek geek is offline
New User
 
Join Date: Oct 2015
Posts: 6
Default

Quote:
Originally Posted by jggimi View Post
OpenBSD 5.9, just released, supports UEFI boot and/or GPT partitions. But the use of foreign file systems is as described above.
Can OpenBSD 5.9 be installed onto a GPT disk without a disklabel at all, as there are more possible codes for partition types? I think FreeBSD doesn't need disklabels on GPT disks when using UFS.
Reply With Quote
  #4   (View Single Post)  
Old 30th March 2016
jggimi's Avatar
jggimi jggimi is offline
More noise than signal
 
Join Date: May 2008
Location: USA
Posts: 5,746
Default

It's a good question, but no. Disklabels are the OpenBSD partitioning schema - real or virtual.

MBRs and GPTs are used on a minority of of the architectures where OpenBSD is supported.
Reply With Quote
  #5   (View Single Post)  
Old 30th March 2016
geek geek is offline
New User
 
Join Date: Oct 2015
Posts: 6
Default

I mean, will it work if no actual disklabel exists on the disk? Just GPT partitions with the FFS file system.
Reply With Quote
  #6   (View Single Post)  
Old 30th March 2016
jggimi's Avatar
jggimi jggimi is offline
More noise than signal
 
Join Date: May 2008
Location: USA
Posts: 5,746
Default

I don't think so, because an MBR/GPT OpenBSD partition is not a filesystem. It's a collection of one or more filesystems, managed via a disklabel. On the six or so MBR (or GPT) architectures, there are two distinct layers of partitioning. On the 11 or so non-MBR architectures, there is only a single layer of partitioning.

Virtual disklabels are allocated only to recognized foreign filesystems (FAT, ext, NTFS, CD9660, ...).
Reply With Quote
  #7   (View Single Post)  
Old 30th March 2016
e1-531g e1-531g is offline
VPN Cryptographer
 
Join Date: Mar 2014
Posts: 333
Default

I am curious where disklabel information is stored on hard driver.
Example: MBR is 512 bytes long and starts at the (CHS – 0, 0, 1).
Where is disklabel's information stored? If I wipe/override FFS filesystem does these information will persist, because it is stored outside FFS filesystem?
I am particularly interested in amd64 architecture.
Reply With Quote
  #8   (View Single Post)  
Old 30th March 2016
jggimi's Avatar
jggimi jggimi is offline
More noise than signal
 
Join Date: May 2008
Location: USA
Posts: 5,746
Default

It varies by architecture, so I'm glad you specified.

On amd64, it uses the second sector of the OpenBSD MBR/GPT partition (partition type A6), or the second sector of the drive if no MBR or GPT is defined.

For clarity, if the partition starts at LBA 64, the disklabel is stored in LBA 65, and if there is no MBR or GPT defined in LBA 0, the disklabel is stored in LBA 1.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Partitioning a Backup Disk? Mantazz FreeBSD Installation and Upgrading 2 29th April 2012 07:34 PM
MBR GPT hybrid partitioning J65nko FreeBSD Installation and Upgrading 2 16th November 2011 09:37 AM
CAPTCHA schemes still easy to bypass J65nko News 8 7th November 2011 08:09 PM
Partitioning for web/mailserver? DrKrall OpenBSD Installation and Upgrading 3 20th November 2009 01:14 PM
Is partitioning still important in installation? Mantazz FreeBSD Installation and Upgrading 14 16th January 2009 08:35 AM


All times are GMT. The time now is 06:52 AM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Content copyright © 2007-2010, the authors
Daemon image copyright ©1988, Marshall Kirk McKusick