Re: should an end user stick to a kernel with an initrd?
On Fri, Sep 27, 2013 at 10:28:01PM +0300, Regid Ichira wrote:
> On Fri, Fri, 27 Sep 2013 13:34:56 -0400, Tom H wrote:
> > On Fri, Sep 27, 2013 at 3:12 AM, Ralf Mardorf wrote:
> > > On Thu, 2013-09-26 at 19:07 -0400, Stephen Powell wrote:
> > >>
> > >> Traditional device names, such as /dev/sda, /dev/sdb,
> > >> (and therefore the partitions on those devices, such
> > >> as /dev/sda1, /dev/sdb1, etc.) are not assigned in a predictable
> > >> manner anymore. This device name assignment can change from one boot
> > >> to the next.
> > >
> > > This never happened on my machine.
> >
> > This won't happen if you have just one disk. ;)
> >
> > On a more serious note, do you really think that all the people
> > maintaining distributions thought "using sdX is far too simple and
> > easy, let's start using human-non-parsable UUIDs?!"
>
> 1. Saying traditional disks names not siigned in a predictable manner
> seem to contradict the fact that one can write
> root=/dev/hdd3
You can certainly write that into the fstab, but that won't guarantee
that the device will be "hdd3"; it might be hdc3, hde3 etc. depending
upon the presence of other devices and the initialisation order.
> in the kernel command line, such as in lilo.
> 2. I have 2 disks. It never happened to me.
Try plugging in a USB storage device during early boot. On some
systems this might end up initialised before the physical HDDs
and then all the hard disks will be renamed and the fstab entries
will be broken. On most systems the SATA drives will be initialised
first, but this isn't guaranteed--a lot of this is asynchronous now;
what if the HDD takes longer to spin up than normal, so gets
registered later? You want guaranteed reliability, and UUIDs/LABELs
give you that; the kernel device names might /seem/ stable on a
given system, but that's really only a result of circumstance, not
by design.
> 4. I think that the LABEL mechanism of /etc/fstab is different,
> predated, and more rigid, from that of a UUID. Again, it seem to
> me supported by some of the comments in
> https://lwn.net/Articles/331818/.
Both are handled by udev today, to give you /dev/disk/by-label
and /dev/disk/by-uuid. I don't think that labels are handled
specially by the kernel in addition to that, since it can be
potentially quite complex and filesystem-specific, but I could
be wrong. Maybe they were in the past, or handled specially
prior to udev?
Regards,
Roger
--
.''`. Roger Leigh
: :' : Debian GNU/Linux http://people.debian.org/~rleigh/
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