Re: Statically nameing a SCSI device

["Gerald V. Livingston II" <gerald.hotplug@sysmatrix.net>]

On Sun, August 12, 2007 11:29, Kay Sievers said:
> On 8/12/07, Gerald V. Livingston II <gerald.hotplug@sysmatrix.net> wrote:
>> On Sun, August 12, 2007 7:24, Kay Sievers said:
>>
>> > On 8/12/07, gerald.hotplug@sysmatrix.net
>> <gerald.hotplug@sysmatrix.net>
>> > wrote:
>> >>
>> >> Now, that being said, it will be a lot easier for *ME* if I always
>> know
>> >> exactly where the SATA drives are located in the plain-old /dev tree
>> and
>> >> if I can call them /dev/sdw or /dev/sdz rather than
>> >> /dev/disk/by-id/ata-WDC_WD2500YS-01S-WD-WCANY1955037
>> >>
>> >> I added this to my local.rules and udevtest says it works great for
>> the
>> >> first drive I already have installed:
>> >>
>> >> KERNEL="sd*[!0-9]", IMPORT="/sbin/scsi_id -g -x $tempnode"
>> >> KERNEL="sd*[!0-9]",
>> >> ENV{ID_SERIAL}="SATA_WDC_WD2500YS-01_WD-WCANY1955037", NAME="sdw"
>> >>
>> >> As I add the other 3 drives I just need to add lines to identify
>> their
>> >> serial numbers and set them at sdx, sdy, and sdz.
>> >
>> > If you change the default name of the nodes, you will never find the
>> > disk a possible error log from the kernel belongs to. You should only
>> > use symlinks.
>> >
>> > /dev/disk/* has probably all you need already without any custom rule.
>>
>> So, better would be:
>>
>> KERNEL="sd*[!0-9]", IMPORT="/sbin/scsi_id -g -x $tempnode"
>> KERNEL="sd*[!0-9]",
>> ENV{ID_SERIAL}="SATA_WDC_WD2500YS-01_WD-WCANY1955037", SYMLINK+="sdw"
>
> Yes, symlinks are better in almost all cases. Still, make sure that
> nobody will ever connect a whole bunch of USB sticks. :) And hope the
> SCSI error handler will hang and repeated connect/disconnect of a
> single block device will produce a real "sdw" device in the kernel.
> It's a kind of a dangerous game to allocate names from the kernel
> namespace.
>
>> The disks will all be the same model so the info in /dev/disk will be
>> the
>> same except for a number or two. Too easy to mix them up if I'm looking
>> for something specific while moving hardware around.
>
> If you use rules later than 60-*.rules, ENV{ID_SERIAL} is already set
> by udev's persistent rules, and there is no need to run scsi_id again.
>
> Kay

On my Debian system install persistent.rules runs at "z20" so I've moved
my SATA rules file to z22_my.sata.rules.

Since nothing on the SYSTEM (only my brain) seems to require /dev/sd"x" to
be static I've also changed the persistent symlinks to be more descriptive
for me. The z22_my.sata.rules file is currently a single line:

KERNEL="sd*[!0-9]",
ENV{ID_SERIAL}="SATA_WDC_WD2500YS-01_WD-WCANY1955037", SYMLINK+="sata1"

This is a Sun E450 Server class machine with hardware plugged into it that
Sun never intended when they built it in the '90s. I haven't decided if I
want to try getting a USB controller installed. ;-)

Gerald


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