SCSI scanner device ownership and permissions

D. Hugh Redelmeier hugh at mimosa.com
Thu Aug 11 07:22:29 UTC 2005


I have trouble using a SCSI scanner on Fedora Core 4.  The trouble
boils down to the fact that /dev/sg0 (where the scanner appears) is
only root-writable, so I have to scan as the superuser -- not safe,
not sensible.

The quickest kludge is to chown /dev/sg0.  But that node gets rebuilt
on each boot (I think) so the chown would need to be done after each
boot.  Pretty annoying.

The console.perms(5) mechanism looks to be a better way than chown: it
systematically changes owners and permissions on files when someone
logs in.

The FC4 console.perms is already set up to handle a class called
<scanner>.  This requires a symlink /dev/scanner -> correct device.
This is good: /dev/sg0 might be some other kind of device at some
point.  Unfortunately, nothing is setting up this symlink.

Whose job is it to set up this symlink?  I would think that
/etc/hotplug/scsi.agent out to do so.  And perhaps do a chown/chmod
because the login might already have happened.

Am I right?  Why does the current scsi.agent not attempt this?

Would scsi.agent get invoked fpr a device that is already there at
boot time?




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