Re: [gentoo-dev] CDRW permissions and devfsd

[Martin Schlemmer]

On Tue, 2002-09-03 at 03:04, Bauno wrote:
> On Tuesday 03 September 2002 02:37, Martin Schlemmer wrote:
> > > [snipped]
> > > The original line in devfsd.conf (that you report above) doesn't work
> > > if sg is compiled as module. You need to set the permissions on the
> > > scsi/bus/.../generic and not on the symbolic links /dev/sg*. I *think*
> > > it's because /dev/sg* doesn't exist (yet) when devfsd tries to apply
> > > the permissions, but I may be wrong.
> >
> > No, the REGISTER means it only gets done when the /dev/sg0 device is
> > registered in the devfs namespace.
> >
> > The real fix for modules, is the line:
> >
> > LOOKUP          ^sg.*$      MODLOAD ACTION sg
> >
> > which cause the "sg" module to be loaded when you "lookup" (try to
> > open) /dev/sg*
>
> I really don't think so (everything's wrapped):
>

I tend to disagree.  At least if not as module:

----------------------------------------------cut-------------------------------------------------
workshop portage # grep root\.cdrw /etc/devfsd.conf 
#REGISTER        ^sg0$       PERMISSIONS root.cdrw 660
workshop portage # ls -l /dev/scsi/host0/bus0/target0/lun0/generic
crw-------    1 workshop root      21,   0 Jan  1  1970 /dev/scsi/host0/bus0/target0/lun0/generic
workshop portage # vim /etc/devfsd.conf 
workshop portage # grep root\.cdrw /etc/devfsd.conf 
REGISTER        ^sg0$       PERMISSIONS root.cdrw 660
workshop portage # killall -HUP devfsd
workshop portage # ls -l /dev/scsi/host0/bus0/target0/lun0/generic
crw-rw----    1 root     cdrw      21,   0 Jan  1  1970 /dev/scsi/host0/bus0/target0/lun0/generic
workshop portage # vim /etc/devfsd.conf 
workshop portage # grep root\.cdrw /etc/devfsd.conf 
#REGISTER        ^sg0$       PERMISSIONS root.cdrw 660
workshop portage # killall -HUP devfsd
workshop portage # ls -l /dev/scsi/host0/bus0/target0/lun0/generic
crw-rw----    1 root     cdrw      21,   0 Jan  1  1970 /dev/scsi/host0/bus0/target0/lun0/generic
workshop portage # chmod 0600 /dev/scsi/host0/bus0/target0/lun0/generic
workshop portage # chown root.root /dev/scsi/host0/bus0/target0/lun0/generic
workshop portage # killall -HUP devfsd
workshop portage # ls -l /dev/scsi/host0/bus0/target0/lun0/generic
crw-------    1 root     root      21,   0 Jan  1  1970 /dev/scsi/host0/bus0/target0/lun0/generic
workshop portage # vim /etc/devfsd.conf 
workshop portage # grep root\.cdrw /etc/devfsd.conf 
REGISTER        ^sg.*$       PERMISSIONS root.cdrw 660
workshop portage # killall -HUP devfsd
workshop portage # ls -l /dev/scsi/host0/bus0/target0/lun0/generic
crw-rw----    1 root     cdrw      21,   0 Jan  1  1970 /dev/scsi/host0/bus0/target0/lun0/generic
workshop portage # 
--------------------------------------------------------------------------------------------------

So it works for changing the permissions on sg0 and sg*.  Like I already
said, because I usually have it compiled in, ill have to recompile and
check if as module.

Also, I think you are going about this the wrong way.  devfsd acts on
triggers.  The default of cdrecord is to probe /dev/sg*, and not
/dev/scsi/host.*/bus.*/target.*/lun.*/generic.  Thus rmmod sg, change to
the "Default Gentoo style" devfsd.conf, killall -HUP devfsd, and then
do: ls /dev/sg0.  After this check the permissions on
/dev/scsi/host0/bus0/target0/lun0/generic.


> Default Gentoo style:
>
> ------------------devfsd.conf-----------------------------------------------
>
> # Give the cdrw group write permissions to /dev/sg0
> # This is done to have non root user use the burner (scan the scsi bus)
> LOOKUP          ^sg.*$      MODLOAD ACTION sg
> #REGISTER        ^scsi/host.*/bus.*/target.*/lun.*/generic    PERMISSIONS
> root.disk 660
> REGISTER        ^sg.*$       PERMISSIONS root.disk 660
>
> --------------devfsd.conf---------------------------------------------------
>
> bauniga root # modprobe sg
> bauniga root # ll /dev/scsi/host0/bus0/target0/lun0/generic
> crw-r-----    1 root     root      21,   0 Jan  1  1970
> /dev/scsi/host0/bus0/target0/lun0/generic
> bauniga root # killall -HUP devfsd
> bauniga root # ll /dev/scsi/host0/bus0/target0/lun0/generic
> crw-rw----    1 root     disk      21,   0 Jan  1  1970
> /dev/scsi/host0/bus0/target0/lun0/generic
>
>
>
>
> Bauno :) style:
>
> ----------------------------devfsd.conf------------------------------------
> # Give the cdrw group write permissions to /dev/sg0
> # This is done to have non root user use the burner (scan the scsi bus)
> LOOKUP          ^sg.*$      MODLOAD ACTION sg
> REGISTER        ^scsi/host.*/bus.*/target.*/lun.*/generic    PERMISSIONS
> root.disk 660
> #REGISTER        ^sg.*$       PERMISSIONS root.disk 660
> --------------devfsd.conf---------------------------------------------------
>
> bauniga root # modprobe sg
> bauniga root # ll /dev/scsi/host0/bus0/target0/lun0/generic
> crw-rw----    1 root     disk      21,   0 Jan  1  1970
> /dev/scsi/host0/bus0/target0/lun0/generic
>
>
> So, I think the Gentoo default devfsd.conf isn't well suited for the sg
> module....
>
> --
> Bauno - Eurydices, oro, properata retexite fata!
> "Even now I can feel it. Buried somewhere deep inside. Watching me...
> waiting. But you know what scares me the most. When I can't fight it
> anymore. When it takes over. When I totally lose control. I like it."
-- 

Martin Schlemmer
Gentoo Linux Developer, Desktop Team Developer
Cape Town, South Africa