Messages in this thread | | | Date | Thu, 12 Jun 2008 22:32:48 -0700 | From | "Shawn Jin" <> | Subject | Re: Force a usb drive to be /dev/sda? |
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First, thanks a lot for the responses, especially to Stefan for the various options. I have further questions on these options to fully understand them.
>> Is there a reason why you can't use filesystem labels or UUIDs? > > Indeed. Shawn, I see these options: > > 1. Mount filesystems by UUID or by label. > Doesn't work with some filesystems.
The bootloader I'm using is LILO. So I have to specify the boot device and the root device in lilo.conf. For example, boot=/dev/sda, root=/dev/sda1. I'm not sure how mounting filesystem by UUID or by label can help. A little bit elaboration will be more helpful.
> 2. Refer to devices by device ID or by device path. > Requires a minimal udev environment which gives you > /dev/disk/by-id or /dev/disk/by-path, or something > similar to udev. People had things like this already > working under Linux 2.4, using programs like devlabel > IIRC. Requires you to set up an initrd with respective > scripts in it. > By-path only works if you never alter the USB topology > and PCI topology. I.e. prefer by-id.
Every USB thumb drive has a unique ID. So will I have to have a different root filesystem image if it's install in a different usb drive if the by-id way is adopted?
> 3. Influence the order of disk probing so that your USB > disk is the first one. Works only if there is at most > one disk on the USB bus and requires you to wait with > insertion or probing of the SATA controller driver (PCI > driver) until after the USB disk was probed by sd_mod. > > There may or may not be very simple ways to do this. > Simplest would be to configure the SATA controller driver > as module and load that module in an rc script after the > root filesystem was mounted. That would actually be much > simpler than option 2, so maybe you want to try this > before 2.
I think I understand this option. Of course this requires an initrd or initramfs, which I need to build.
> 4. Last resort: Hack sd_mod to defer any probes until after > the first probe of an USB attached disk. Requires some > experience in kernel driver programming.
As you said, this is the last resort, which I also try to avoid. ;-)
-Shawn.
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