Re: Creating /dev/scanner

From: Douglas Gilbert (dgilbert@interlog.com)
Date: Thu Sep 07 2000 - 20:17:29 PDT

  • Next message: M. Peck Dickens: "Re: Creating /dev/scanner"

    Randolph Bentson wrote:
    >
    > On Fri, Sep 08, 2000 at 01:58:54AM -0400, M. Peck Dickens wrote:
    > > Hi there,
    > >
    > > OK, I've recieved my Fujitsu 600c and it works great under SANE!. Now, I want to
    > > create /dev/scanner and soft link it to /dev/sgd. My question is how do I do
    > > this properly and then give /dev/scanner the correct permissions so I can
    > > use SANE as joe user instead of as root and still have security in place?
    >
    > That's good news.
    >
    > You cannot use permissions on "/dev/scanner" to open access.

    Not if it's a symbolic link. However you could use mknod
    to make it point to the same device as /dev/sgd :
       mknod /dev/scanner c 21 3

    and then set the permissions on it. Hopefully this wouldn't
    confuse SANE. Probably not a smart idea though.

    > Provided you've got a stable hardware environment, i.e., one
    > which doesn't have SCSI devices added and removed on a whim,
    > you can add a group "sane_oper", add whomever you want to that
    > group, "chmod 660 /dev/sgd" and "chgrp sane_oper /dev/sgd".
    >
    > At least that's what I do.
    >
    > If you have SCSI devices added and removed, the device used to
    > access the scanner will change. You'll have to change which
    > device has the appropriate permissions. I believe the device
    > filesystem in 2.4 kernel will address this problem.

    There is also a user space utility called scsidev that could be
    useful in this regard (and it works on all versions of Linux). It
    allows aliases such as /dev/scanner to be created pointing at the
    (sg) device that matches a given set of parameters. For example,
    if you knew that your scanner has scsi id=5 then the following
    could be placed in the file /etc/scsi.alias :
        id=5, devtype=generic, alias=scanner

    See http://www.garloff.de/kurt/linux/scsidev
    What I have described above is documented in its manpage.

    Doug Gilbert

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