CentOS - Mar 2019 - What files to edit when changing the sdX of hard drives?

On Thu, Feb 28, 2019 at 05:19:49PM +0100, Nicolas Kovacs (info at microlinux.fr)
wrote:
> Le 28/02/2019 ? 04:12, Jobst Schmalenbach a ?crit?:
> > I want to lock in the SDA/SDB/SDC for my drives
> 
> In short : use UUIDs or labels instead of hardcoding /dev/sdX.
I **KNOW** how to use UUID's ... this is NOT the reason why I am doing this!


I *NEED* the order of the disks to be SDA(1st BIOS drive) SDB(2nd BIOS drive)
SDC(3rd BIOS drive) and not SDA (1st BIOS drive) SDB(3rd BIOS drive) SDC (2nd
BIOS drive).

Reason: it stuffs up the use of grub2* utilities leaving behind a bunch of error
messages.
The SDA (1st BIOS drive) and SDB (2nd BIOS drive) are part of a MDADM raid(1)
system.

As soon as I plug in the third drive, the OS (or systemD) decides to put it into
the SDB spot - I do NOT want that.
When I the use any of the grub2 utils I end up with "missing drive"
errors.

If I leave the drive out NO problem. I have managed twice to have the machine
booting with the third drive as SDC, when that happens I I do not get any error
messages.



Jobst


-- 
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  | | |0|   Barrett & Sales Essentials
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On 2/28/19 10:04 PM, Jobst Schmalenbach wrote:
> On Thu, Feb 28, 2019 at 05:19:49PM +0100, Nicolas Kovacs (info at
microlinux.fr) wrote:
>> Le 28/02/2019 ? 04:12, Jobst Schmalenbach a ?crit?:
>>> I want to lock in the SDA/SDB/SDC for my drives
>>
>> In short : use UUIDs or labels instead of hardcoding /dev/sdX.
> 
> I **KNOW** how to use UUID's ... this is NOT the reason why I am doing
this!
> 
> 
> I *NEED* the order of the disks to be SDA(1st BIOS drive) SDB(2nd BIOS
drive) SDC(3rd BIOS drive) and not SDA (1st BIOS drive) SDB(3rd BIOS drive) SDC
(2nd BIOS drive).
> 
> Reason: it stuffs up the use of grub2* utilities leaving behind a bunch of
error messages.
> The SDA (1st BIOS drive) and SDB (2nd BIOS drive) are part of a MDADM
raid(1) system.
> 
> As soon as I plug in the third drive, the OS (or systemD) decides to put it
into the SDB spot - I do NOT want that.
> When I the use any of the grub2 utils I end up with "missing
drive" errors.
Try to switch physical connections of second and third drives, then you 
most likely will have the correct "BIOS" order of physical drives. As,
as far as I understand, the letters are assigned in the order the bus 
scan discovers drives (or - though less likely - in reverse order, at 
least reverse order once was for network interfaces, like discovered 
ones were pushed into stack, and then used in the order they were popped 
out of the stack).

Valeri
> 
> If I leave the drive out NO problem. I have managed twice to have the
machine booting with the third drive as SDC, when that happens I I do not get
any error messages.
> 
> 
> 
> Jobst
> 
> 
-- 
++++++++++++++++++++++++++++++++++++++++
Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247
++++++++++++++++++++++++++++++++++++++++

On Fri, Mar 01, 2019 at 09:48:55AM -0600, Valeri Galtsev (galtsev at
kicp.uchicago.edu) wrote:
> 
> 
> On 2/28/19 10:04 PM, Jobst Schmalenbach wrote:
> > On Thu, Feb 28, 2019 at 05:19:49PM +0100, Nicolas Kovacs (info at
microlinux.fr) wrote:
> > > Le 28/02/2019 ? 04:12, Jobst Schmalenbach a ?crit?:
> > > > I want to lock in the SDA/SDB/SDC for my drives
> > > 
> > > In short : use UUIDs or labels instead of hardcoding /dev/sdX.
> > 
> > I **KNOW** how to use UUID's ... this is NOT the reason why I am
doing this!
> 
> Try to switch physical connections of second and third drives, then you
most
> likely will have the correct "BIOS" order of physical drives. As,
as far as
It seems I need to go that way as I learned that you cannot use UDEV to swtich
the names of sdX as assigned by the kernel. You can only ADD (as in make an
extra name) but not RENAME :-(.

It's weird though even in the BIOS they are assigned

 SDA (mirror 1)
 SDB (mirror 2)
 SDC (extra rsync/backup drive).

It's not nice, though. The problem arises because I will NEVER have a
backup/rsync drive in a system when I do an install that includes resetting of
partition tables of SOME of the drives - a backup drive is a holy grail.

So I created the mirror (i.e. partitioning and starting mdadm) withou the backup
drive.

As soon as I put that one back in I cannot use and of the grub2 utils without
those errors "missing drive" as suddenly the the mirrors are on SDA
and SDC.

So there must be some bug somewhere as the grub2 utils do not look at the UUIDs
but somehow at the hardware sdX.

Jobst


-- 
Do Lipton Tea employees take coffee breaks?

  | |0| |   Jobst Schmalenbach, General Manager
  | | |0|   Barrett & Sales Essentials
  |0|0|0|   +61 3 9533 0000, POBox 277, Caulfield South, 3162, Australia