Bug 767716

Summary: Can not unset "DOS-compatible mode" using fdisk
Product: Red Hat Enterprise Linux 6 Reporter: Madison Kelly <mkelly>
Component: util-linux-ngAssignee: Karel Zak <kzak>
Status: CLOSED NOTABUG QA Contact: qe-baseos-daemons
Severity: high Docs Contact:
Priority: unspecified    
Version: 6.2   
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2011-12-15 11:39:16 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Attachments:
Description Flags
lspci from one of the effected nodes
none
dmidecode from one of the effected nodes. none

Description Madison Kelly 2011-12-14 18:02:14 UTC 
Created attachment 546845 [details]
lspci from one of the effected nodes

Description of problem:

In my test system, I have a single SATA platter drive. When I modify the disk using 'fdisk -u /dev/sda', it alerts that "DOS-compatible mode is deprecated". I press 'c' to disable this, 'w' write out the changes and reboot. Once rebooted, I try to again configure the disk and get the same message.

Version-Release number of selected component (if applicable):

util-linux-ng-2.17.2-12.4.el6.x86_64

How reproducible:

For me, 100% across two nodes. Unknown if it's hardware-specific.

Steps to Reproduce:
1. Use fdisk to disable DOS compatible mode.
2. Write out the changes and reboot.
3. Again open the disk using fdisk, DOS compatible mode still enabled.
  
Actual results:

DOS compatible mode remains enabled.

Expected results:

DOS compatible mode is disabled.

Additional info:

* The mainboard is a Tyan S5510GM3NR (http://tyan.com/product_SKU_spec.aspx?ProductType=MB&pid=698&SKU=600000217)
* The hard drive is a Seagate ST9500420ASG (http://www.seagate.com/ww/v/index.jsp?vgnextoid=3a07bfafecadd110VgnVCM100000f5ee0a0aRCRD&locale=en-US)

This is a very basic setup; No RAID controller or otherwise special configuration.

Kernel;
Linux an-node01.alteeve.com 2.6.32-220.el6.x86_64 #1 SMP Wed Nov 9 08:03:13 EST 2011 x86_64 x86_64 x86_64 GNU/Linux

lspci and dmidecode attached.
Comment 2 Madison Kelly 2011-12-14 18:03:25 UTC 
Created attachment 546846 [details]
dmidecode from one of the effected nodes.
Comment 3 Karel Zak 2011-12-15 11:39:16 UTC 
(In reply to comment #0)
> In my test system, I have a single SATA platter drive. When I modify the disk
> using 'fdisk -u /dev/sda', it alerts that "DOS-compatible mode is deprecated".
> I press 'c' to disable this, 'w' write out the changes and reboot. Once
> rebooted, I try to again configure the disk and get the same message.

This is correct behaviour. The (non)DOS mode is about a way how fdisk calculates
some offsets and partitions sizes. The mode is not enabled or disabled according to on-disk data (partition table).

Note that this is temporary solution for RHEL6 for backward compatibility with initial RHEL6 release; RHEL>=7 will use the non-DOS mode by default and 'u' and 'c' commands will be unnecessary.