On Mon, Dec 09, 2013 at 11:35:03AM -0800, ToddAndMargo wrote:
> 
> Bug 836696 has been driving me nuts for years.  This is
> where you drop to fsck on boot for the backup drive,
> but you can't do anything with the drive when you get
> to maintenance mode.
> 
> And, I finally figured out what is causing this.  My
> OS and my backup drive's devices are randomly reversing
> themselves at boot.  For details, see comment #37:
> 
>     https://bugzilla.redhat.com/show_bug.cgi?id=836696#c37
> 
> Hope no one else has to figure this one out the hard way,
> as I did.
> 

Doh! This linux "feature" bites rookie and wizard all the same.

Linux assigns the sdN names in the order that devices are discovered
and this order is not deterministic - SCSI, SATA and USB may all be scanned
at the same time mixing up all the names each time. Mr. Torvalds cares
about this not one bit, he has only a single drive inside his mac air
and no usb ports to accidentally confuse things by leaving a usb drive
connected during reboot.

Therefore, on linux, you cannot put "/dev/sda1" & co into /etc/fstab.
You have to mount filesystems by UUID or by label. This was true and
worked quite well for ages now. (Even with IDE disks, the /dev/hda, /dev/hdb, etc
assignement was not super fixed - it depended on the order that IDE
host adapters were initialized and this order has been known to change
between different linux releases).

-- 
Konstantin Olchanski
Data Acquisition Systems: The Bytes Must Flow!
Email: olchansk-at-triumf-dot-ca
Snail mail: 4004 Wesbrook Mall, TRIUMF, Vancouver, B.C., V6T 2A3, Canada