SATA internal disk and external drive - device changes

Rashkae ubuntu at
Fri Feb 15 04:27:23 UTC 2008

Ed Jabbour wrote:
> Internal SATA drive designated as sdax.  I attached an external hard drive 
> enclosure via USB.  Instantly recognized as sdb.  I formatted the external 
> and successfully transferred files back and forth.  However, on a reboot with 
> the external left on, I have the internal as sdbx and the external as sdc and 
> sdc1.  Turned the external off and rebooted and I get sda and sdb.  Any 
> advice, hints, pointers, etc. appreciated.  Relevant fstab entry:
> /dev/sdb1 /mnt/external ext3 user,atime,noauto,rw,nodev,noexec,nosuid 0 0

These are the kinds of reasons why Ubuntu now uses the UUID syntax in 
the fstab file.  Modern Bioses can re-organize the order of hard drives 
every which way, and Linux, by design, will change drive designations 
depending on which drivers get loaded first.  You need to identify what 
the UUID of your partitions are, then put that in your fstab file 
instead of /dev/sdb1 (and all your other drives as well)

> Lastly, the external is one partition; I thought so, anyway.  Why sdb and 
> sdb1?  sdb won't mount - wrong fs type, bad superblock stuff.  Did not format 
> correctly?

yes, you formatted your drive correctly. sdb gives direct access to your 
whole drive, sdb1 is access to the first (and in this case, only 
partition) on this drive.  I wonder if it's possible in linux to create 
a filesystem directly on a drive without any partitions?  Even if it 
would work, I'm not sure there would be any advantage to doing something 
like that.  However, suppose you had multiple partitions, sdb1, sdb2, 
sdb5, etc.  you could, if you wanted, erase everything on the hard 
drive, including the partition table, with a command like dd 
if=/dev/zero of=/dev/sdb  (Warning: I don't advsise anyone try this 
command unless they know what they are doing).  The point is, by 
creating a device entry for /dev/sdb that gives access directly to the 
hard drive, utilities like fdisk are able to write/modify the partition 
table, boot loaders can write what they need in the boot sector, etc.

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