[olug] How to force internal HDD to be sda?

Kevin D. Snodgrass kdsnodgrass at yahoo.com
Thu Sep 16 04:22:20 UTC 2010

--- On Wed, 9/15/10, Christopher Cashell <topher-olug at zyp.org> wrote:
> It's actually pretty logical.  Disks are named in the
> order in which
> the system sees them.  Apparently, USB is getting
> scanned for disks
> before IDE/SATA/SCSI is.  Thus, if your external disk
> is connected
> prior to boot, it ends up as /dev/sda.  Otherwise, it
> gets added as
> the next available disk when connected (typically
> /dev/sdb,
> apparently).

I suspected as much.

> > Is there some way I can force whatever is doing this
> (I'm guessing udev, since this problem starting showing up
> with it's introduction) to assign the internal to /dev/sda?
> Yes.  udev is the correct place to handle this,
> provided the currently
> available information (see below) isn't good enough. 

It isn't.  As I have said (many times now), I want the internal drive to be /dev/sdX, where X stays the same regardless of external drives, thumb drives, etc at bootup.

> First question,
> do you *need* /dev/sda and /dev/sdb to point to these
> specific drives?

Not "specific", just the same each boot, regardless of what is plugged in.  I'm not concerned about the USB drives, they come and go.  I just want the internal to be /dev/sdX, where X doesn't change between reboots.  It really is a simple idea.  Think "the way it used to be", i.e. before udev.

> If they absolutely must be /dev/sda or /dev/sdb,
> respectively, then
> you need to write/edit some udev rules in
> /etc/udev/rules.d/.
> Depending on your distribution, you may have some samples
> there that
> you can work from.  If not, you can find references

Unfortunately, Fedora 13 doesn't have anything useful there, or in /lib/udev or any place else I have looked.

> and documentation
> on the web.  Basically, you'll need to write a rule
> for udev so that
> when a disk is found, it is checked a certain way (commonly
> using
> /lib/udev/scsi_id, or something similar), and depending on
> the
> information found about that disk, it is
> named/renamed/aliased
> appropriately.

Trying to find the correct search term for Google to present me with useful results.

Kevin D. Snodgrass


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