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.
-- Bruce
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