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List:       linux-390
Subject:    Re: Devices disappeared from /dev
From:       Mark Post <mpost () novell ! com>
Date:       2010-02-24 17:33:42
Message-ID: 4B851CA60200006D0009E373 () novprvlin0050 ! provo ! novell ! com
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> > > On 2/24/2010 at 09:48 AM, "van Sleeuwen, Berry"
<Berry.vanSleeuwen@atosorigin.com> wrote: 
> Looking at a SLES10 machine, there it is the same:
> 
> nlzlx114:~ # ll /dev/disk/by-path/
> total 0
> lrwxrwxrwx 1 root root 11 Feb 14 00:38 ccw-0.0.0200 -> ../../dasda
> lrwxrwxrwx 1 root root 12 Feb 14 00:38 ccw-0.0.0200-part1 ->
> ../../dasda1
> 
> So here too, if dasda1 would have been deleted in the /dev/ directory
> the by-path wouldn't work either.

In SLES10 and higher, /dev is actually a tmpfs device.  That is, it only exists in \
memory, so it is dynamically created each time the system is rebooted.  Udev is \
responsible for populating /dev.  In SLES9, that was problematic, to say the least, \
but the contents of /dev were on real disk, and so more persistent.  Most people \
really needed to depend on the /dev/dasd?? names.  If the "dasd=" parm wasn't \
specified in zipl.conf, then the mkinitrd command was the one to determine which DASD \
volumes got activated at boot time, via the /linuxrc script in the initrd.

If you're going to be moving disks (or guests) anywhere, it's really a good idea to \
check the contents of /linuxrc in the initrd to be sure you're going to get what you \
expect.  For SLES10 and higher, using /dev/disk/by-path/ is far simpler and more \
reliable than any other naming scheme.


Mark Post

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