Re: Read-only USB scan

[Ron Johnson <ron.l.johnson@cox.net>]

On 12/21/08 05:01, Bhasker C V wrote:
> Ron Johnson wrote:
> > <div class="moz-text-flowed" style="font-family: -moz-fixed">(Please 
> > don't top-post.)
> >
> > On 12/20/08 18:18, Bhasker C V wrote:
> > > Hi,
> > >
> > >  hdparm -r1 /dev/sda
> > >   works and I get this output when I read back the information with 
> > > plain '-r'
> > >
> > >   $ sudo hdparm -r /dev/sda
> > >
> > > /dev/sda:
> > >  readonly     =  1 (on)
> > >
> > >
> > > Does this make it really read-only ?
> >
> > That's what happens on my Firewire/SATA hard drive.
> >
> > # hdparm -r1 /dev/sdc1
> >
> > /dev/sdc1:
> >  setting readonly to 1 (on)
> >  readonly      =  1 (on)
> >
> > # mount -v /data/02
> > mount: block device /dev/sdc1 is write-protected, mounting read-only
> > /dev/sdc1 on /data/02 type ext3 (ro)
> >
> > # dd count=10 if=/dev/hda1 of=/data/02/foo.bar
> > dd: opening `/data/02/foo.bar': Read-only file system
> >
> >
> > > My harddisk is having a PV and then a VG ... LV which if i mount, 
> > > still is able to write to it ? [ VG activation is successful ]
> > >
> > > (dont know if 'write' means really write a large file but I checked 
> > > using touch command and I am still able to create the file)
> > >
> > > My kernel is 2.6.21.1
> > >
> > > Is there anything I am missing here ?
> >
> > Since you've got so many layers logicalness between the app and the 
> > spindles, maybe you aren't really writing to the spindle you think you 
> > are writing to?  Or LVM is setting the read flag?
>
> I tried this too ... But i am sure that the data is getting written to 
> be spindle. I deactivated the usb drive and then re-activated the VG and 
> LVs in it and could see the data writeen intact !
>
> So, my guess is that hdparm -r1 does not work on USB scanned devices and 
> there is no method to make the device read-only [unless we try to stick 
> out head into the physical hardware ] ? Is that what we are concluding ?

Well, *you*, who are closer to the problem than I, are concluding it.

All I *know* is that "-r1" works on SCSI-over-Firewire and that it 
apparently does not work on LVM over SCSI-over-USB.  Unless you are 
doing something "else" which seems so innocuous that you've failed 
to mention it.

--
Ron Johnson, Jr.
Jefferson LA  USA

I like my women like I like my coffee - purchased at above-market
rates from eco-friendly organic farming cooperatives in Latin America.