[systemd-devel] Booting with USB flash disk installed results in wrong disk numbering

Colin Guthrie gmane at colin.guthr.ie
Tue Feb 5 06:12:32 PST 2013

'Twas brillig, and Baurzhan Muftakhidinov at 05/02/13 13:30 did gyre and
> Alright,
> I've tried on netbook and on relatively powerful laptop to boot 10 times
> latest ArchLinux's archboot image from the USB drive.
> On laptop, hard disk was /dev/sda 10 times out of 10 tries,
> On netbook, only 3 times hard disk was /dev/sda and 7 times USB drive
> became /dev/sda.
> What concerns me here is that there is no consistency on less powerful machine.
> So I should just believe in the RANDOM choice on every boot on my netbook?
> On Debian with sysvinit it works just fine. When I change sysvinit to
> systemd (kernel and udev are the same),
> I see the situation I am talking here.
> This is what I asked for, maybe there is some kind of timeout for
> detecting disks.

As others have already commented, you simply should not use /dev/sd* at
all in any definition either on the kernel command line or in your fstab.

Distros switched many years ago to using UUIDs for fstab and kernel
command line entries - long before systemd existed.

Forget those /dev/sd* names, they are meaningless.

Use the UUID or use the LABEL. Anything else is just going to break in
confusing ways. Solutions for the problem already exist - better just to
use them.



Colin Guthrie

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