On Sun, 7 Oct 2018 at 16:43, Bruce Dubbs <[email protected]> wrote:

> On 10/07/2018 12:58 AM, Ken Moffat wrote:
> > On Sun, Oct 07, 2018 at 07:25:55AM +0200, Theodore Driscoll wrote:
> >>     Hi
> >>
> >>     my daily-use machine runs openSuse. To experiment with LFS I added a
> >>     second SATA HDD.
> >>
> >>     Initially the Suse  drive was /dev/sda, the new, unpartitioned,
> drive
> >>     /dev/sdb.
> >>
> >>     But I rebooted once more. Now Suse has swapped the names, so what
> used to
> >>     be /dev/sda is now /dev/sdb and vice-versa. If I reboot again, the
> names
> >>     sometimes swap back, sometimes do not.
> >>
> >>     Section 2.4, Creating a New Partition, doesn't allow for this
> situation -
> >>     it assumes the drive names are persistent.
> >>
> >>     Has anyone else encountered this situation, and found a way around
> it?
> >>
> >>     Cheers
> >>     Ted
> >
> > I've never seen an _internal_ drive change its device across reboots
> > on the same kernel, except when other internal  drives were added or
> > removed.  And in that situation the device names persist for as long
> > as "this drive is plugged in here, that drive is plugged in there".
> >
> > Hmm, I suppose it is possible if all the drivers are on an initrd
> > (most distros, including Suse) and there is some variability in
> > timings - but it seems unlikely.
> >
> > So I guess that this is an external drive ?  If so, expect pain when
> > you complete LFS and try to boot an external drive from grub.
> >
> > With Suse, I assume it mounts by UUID - but I've been able to avoid
> > that approach on my own systems (I think there are two variants of
> > UUID-style, only one of which is supported without an initrd - and
> > LFS doesn't use initrds.)
> >
> > For ext4, you might be able to use e2label to label the LFS
> > filesystem, and then mount with label= instead of /dev/sdXN.  But
> > I'm not sure about how well that would work when you finish LFS and
> > try to boot it, if you have other partitions which you wish to mount
> > on the Suse drive (e.g. /boot, /home) and it won't work for swap.
> >
> > But I'm sure somebody will be able to offer details on the variants
> > of UUID mounting and how to fix your problem.  In the meantime,
> > "patience, and good luck!".
>
> I agree with Ken.  I've never had the drive order change for internal
> SATA (or older SCSI or IDE) drives.  USB drives, yes.  I'm not sure
> about SATA, but for the older SCSI drive the order was determined by HW.
>   I suspect the same for SATA.
>
> It is usually possible to change the boot drive in most system firmware.
>
> The way to ensure that GRUB loads the correct root file system is to use
> PARTUUID=<uuid> on the kernel command line.  No initrd is required but a
> GUID Partition Table (GPT) is required.  Most distros use filesystem
> UUIDs, but that requires an initrd.
>
> Booting to a USB drive may require rootdelay=10 on the kernel command line.
>

If using gdisk a label can also be applied at the same time as partitioning.

Richard
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