UUID question

[Jay Ridgley]

Nils wrote:

Date: Sun, 17 Aug 2008 15:07:22 +0200 From: Nils Kassube 
<kassube at gmx.net> Subject: Re: UUID question To: 
ubuntu-users at lists.ubuntu.com Message-ID: 
<200808171507.22272.kassube at gmx.net> Content-Type: text/plain; 
charset="iso-8859-1" Jay Ridgley wrote:

> > I have two partitions that have UUIDs assigned that were assigned
> > during the upgrade to edgy, /dev/sda1 and /dev/sda5, the first is
> > mounted as / and the second one as swap. The names have changed due to
> > the SCSI controller being assigned /dev/sda since sudo fdisk -l shows
> > them as /dev/sdb1 and  /dev/sdb5.
>   

The SCSI controller is definitely not assigned a device name, only the 
disks connected to the controller will get device names. However I can't 
tell you why you don't have /dev/sda* entries.

--> My comment
-->  It was used for my HP Photosmart C3180 All-in-ONE... see below

> > I also have  three others  that do not,  /dev/hdd,  /dev/sdc1 and
> > /dev/sdc2,  these are mounted as /media/cdrom, /home and /archive
> > respectively.
> >
> > It appears that my scsi cdrom /dev/scd1 is not included in /etc/fstab,
> > however, the other cdrom is included as /dev/hdd with a mount point of
> > /media/cdrom0.
> >
> > My question is are the UUIDs required or can I change them back to the
> > "old fashioned" names (/dev/sdb1 and /dev/sdb5) that I have used for
> > years with  Linux and various other UNIX systems? 
>   

Well, you _can_ change the entries to device names and it will work, if 
the device names are _always_ the device names you have now. But as you 
mentioned in your first paragraph, you can't be sure that the disk which 
is now at sdb is always sdb - it has been sda before. At least that's how 
I understand it. Now, if device names change, after you have renamed the 
fstab entries to device names, your system won't work any longer. May I 
ask why you want to use device names in your fstab?

--> My comment:

-->  I am just more used to that notation, however, after some more research I think I need to learn the new method... see below

> > Can I safely create 
> > an entry in /etc/fstab for the SCSI CDROM?
>   

Sure.

--> My comment:

-->  I think I need to use a UUID here also...

Nils

Derek ALSO wrote:

--snip my OP--

Here we go again...

Of course you can change back to old fashioned names - but why would you
expect this to continue to work?  Your devices have changed names before,
and they'll likely change again.  You're _much_ safer to use the UUIDs. 
And sure you can create an entry for the SCSI CD.

-- derek

--> My comment:

-->  I was not aware of device names changing during installation, however, as you both may see below they do..

--> Additional info below ---


jay at polar:~$ lsscsi
[0:0:0:0]    disk    SEAGATE  ST318404LW       0006  /dev/sdb
[0:0:1:0]    disk    SEAGATE  ST318404LW       0006  /dev/sdc
[0:0:4:0]    tape    Seagate  STT20000N        6A51  /dev/st0
[0:0:5:0]    cd/dvd  YAMAHA   CRW8824S         1.00  /dev/scd0
[3:0:1:0]    cd/dvd  SAMSUNG  CD-ROM SC-148C   B100  /dev/scd1
[4:0:0:0]    disk    HP       Photosmart C3180 1.00  /dev/sda

jay at polar:~$ lsusb
Bus 002 Device 001: ID 0000:0000  
Bus 001 Device 004: ID 03f0:5611 Hewlett-Packard PhotoSmart C3180
Bus 001 Device 003: ID 058f:6254 Alcor Micro Corp. 
Bus 001 Device 001: ID 0000:0000

jay at polar:~$ cat /etc/fstab
# /etc/fstab: static file system information.
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    defaults        0       0
# /dev/sda1 -- converted during upgrade to edgy
UUID=aa505a5b-90e4-4f99-94d3-3adc17db5e41 / ext3 defaults,errors=remount-ro 0 1
# /dev/sda5 -- converted during upgrade to edgy
UUID=abe9cd12-9e62-4c8a-beb3-d1e022ba02f9 none swap sw 0 0
/dev/hdd        /media/cdrom0   udf,iso9660 user,noauto     0       0
# next lines added by CDJ Systems - 06/28/08 
/dev/sdc2       /home           ext3    rw              0       2
/dev/sdc1       /archive        ext3    rw,noauto       0       2

There are some interesting things in the above information:

1. The /dev/sda device is really my printer that is connected via  USB and I would to hazard a guess refers to the scanner. 
    Why is it identified as a SCSI disk?

2. The SAMSUNG CDROM is NOT a SCSI device but is connected via the IDE bus.
 
3. The device /dev/hdd does not exist (ls -l /dev/hdd shows that) and I would assume a mount command would also fail. 

The question now becomes how do I go about generating UUIDs for these other devices (those without them) and get those identifiers properly assigned?

Sorry for the length of this but want to avoid problems down the road...

Cheers,
Jay

-- 


Jay Ridgley
jridgley2 at austin.rr.com
Registered Linux User ID - 9115
Registered Ubuntu User ID - 23320