turn off auto assembly

turn off auto assembly

[Stefan /*St0fF*/ Hübner]

Hi List,

i have multiple technicians computers where I need the md-modules f.e.
for recoveries and such.  But these computers are also used to just
diagnose failing drives.

Now I have the effect that upon plugging in drives that formerly were
part of an array, the md_mod modules gets loaded and tries to
auto-assemble arrays.  This disturbs the diagnosis.

I've tried raid=noautodetect as kernel commandline, and I grepped the
source for the MODULE_PARM_DESC macro, which yielded no (useful) result.
 This "automagic" behaviour happens since 2.6.36.

Is there any way to turn it off - i.e. that I need to explicitly issue
mdadm commands to bind any drive to any array?

Cheers,
Stefan

Re: turn off auto assembly

[Mario 'BitKoenig' Holbe]

Stefan /*St0fF*/ Hübner <stefan.huebner@stud.tu-ilmenau.de> wrote:
> Now I have the effect that upon plugging in drives that formerly were
> part of an array, the md_mod modules gets loaded and tries to
> auto-assemble arrays.  This disturbs the diagnosis.
> I've tried raid=noautodetect as kernel commandline, and I grepped the
> source for the MODULE_PARM_DESC macro, which yielded no (useful) result.
>  This "automagic" behaviour happens since 2.6.36.

Are you sure this autodetection is triggered by the module?
And are you sure this behaviour is bound to this specific kernel
version?

In-Kernel auto-assembly is usually not active when md is compiled as
module. Probably in your case this is some udev-triggered assembly?


regards
   Mario
-- 
Programmieren in C++ haelt die grauen Zellen am Leben. Es schaerft
alle fuenf Sinne: den Schwachsinn, den Bloedsinn, den Wahnsinn, den
Unsinn und den Stumpfsinn.
                                 [Holger Veit in doc]

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Re: turn off auto assembly

[Stefan Hübner]

Am 02.12.2010 22:16, schrieb Mario 'BitKoenig' Holbe:
> Stefan /*St0fF*/ Hübner <stefan.huebner@stud.tu-ilmenau.de> wrote:
>> Now I have the effect that upon plugging in drives that formerly were
>> part of an array, the md_mod modules gets loaded and tries to
>> auto-assemble arrays.  This disturbs the diagnosis.
>> I've tried raid=noautodetect as kernel commandline, and I grepped the
>> source for the MODULE_PARM_DESC macro, which yielded no (useful) result.
>>  This "automagic" behaviour happens since 2.6.36.
> Are you sure this autodetection is triggered by the module?
> And are you sure this behaviour is bound to this specific kernel
> version?
>
> In-Kernel auto-assembly is usually not active when md is compiled as
> module. Probably in your case this is some udev-triggered assembly?
>
>
> regards
>    Mario
Hi Mario,

thanks for the hint, I'll check the rules files then ...

Greetings from nebenan sozusagen,
Stefan
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Re: turn off auto assembly

[Neil Brown]

On Thu, 2 Dec 2010 22:16:25 +0100 Mario 'BitKoenig' Holbe
<Mario.Holbe@TU-Ilmenau.DE> wrote:

> Stefan /*St0fF*/ Hübner <stefan.huebner@stud.tu-ilmenau.de> wrote:
> > Now I have the effect that upon plugging in drives that formerly were
> > part of an array, the md_mod modules gets loaded and tries to
> > auto-assemble arrays.  This disturbs the diagnosis.
> > I've tried raid=noautodetect as kernel commandline, and I grepped the
> > source for the MODULE_PARM_DESC macro, which yielded no (useful) result.
> >  This "automagic" behaviour happens since 2.6.36.
> 
> Are you sure this autodetection is triggered by the module?
> And are you sure this behaviour is bound to this specific kernel
> version?
> 
> In-Kernel auto-assembly is usually not active when md is compiled as
> module. Probably in your case this is some udev-triggered assembly?

s/usually not/never/

With a sufficiently recent mdadm, you can put
   AUTO -all

in mdadm.conf to disable auto-assembly.

Alternately, find the udev rule (/lib/udev/rules.d/64-md-something) and 
comment out the bit where it runs "mdadm -I" or "mdadm --incremental".

NeilBrown


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Re: turn off auto assembly

[Stefan Hübner]

Thanks for all the hints.

There were no udev-rules on the computers, so I fixed the problem using
Neil's hints: 'echo "AUTO -all" >> /etc/mdadm.conf'.

Cheers,
Stefan

P.S.: as the "auto assemble everything with 0xfd partition type" may
become destructive at times (I have to deal a lot with damaged arrays),
I'd suggest not to make it the default setting.  But the other side is:
most people who set up a RAID would want to have it this way, so I guess
it's my duty to make sure no autoassembly on my technicians' computers
happens, unless I tell mdadm to do so...

P.P.S.: The behaviour might very well have come with the update to
mdadm-3.1.4, which may well have come nearly in parallel with me
updating the kernels... (as Gentoo stable jumped from 3.0 to 3.1.4 in
late October, at the beginning of November I updated the kernels...)

Am 03.12.2010 02:30, schrieb Neil Brown:
> On Thu, 2 Dec 2010 22:16:25 +0100 Mario 'BitKoenig' Holbe
> <Mario.Holbe@TU-Ilmenau.DE> wrote:
>
>> Stefan /*St0fF*/ Hübner <stefan.huebner@stud.tu-ilmenau.de> wrote:
>>> Now I have the effect that upon plugging in drives that formerly were
>>> part of an array, the md_mod modules gets loaded and tries to
>>> auto-assemble arrays.  This disturbs the diagnosis.
>>> I've tried raid=noautodetect as kernel commandline, and I grepped the
>>> source for the MODULE_PARM_DESC macro, which yielded no (useful) result.
>>>  This "automagic" behaviour happens since 2.6.36.
>> Are you sure this autodetection is triggered by the module?
>> And are you sure this behaviour is bound to this specific kernel
>> version?
>>
>> In-Kernel auto-assembly is usually not active when md is compiled as
>> module. Probably in your case this is some udev-triggered assembly?
> s/usually not/never/
>
> With a sufficiently recent mdadm, you can put
>    AUTO -all
>
> in mdadm.conf to disable auto-assembly.
>
> Alternately, find the udev rule (/lib/udev/rules.d/64-md-something) and 
> comment out the bit where it runs "mdadm -I" or "mdadm --incremental".
>
> NeilBrown
>
>
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