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Thread: Possible problem with /dev/*lp* in new installations

  1. #1
    Join Date
    Mar 2010
    Location
    Lost in Contemplation
    Beans
    18
    Distro
    Ubuntu 9.10 Karmic Koala

    Possible problem with /dev/*lp* in new installations

    I recently installed Ubuntu 9.10 and have been trying to set up a USB printer.

    I hit a problem which I eventually diagnosed as being the ownership of /dev/usb/lp0.

    First, the symptom:

    ~$ cat Test > /dev/usb/lp0
    bash: /dev/usb/lp0: Permission denied

    The initial diagnosis:

    ~$ ls -l /dev/usb/lp0
    crw-rw---- 1 root lp 180, 0 2010-03-23 21:39 /dev/usb/lp0

    Notice the lp group? When I checked group properties, this group did not have any members - not even root!!!

    The default for CUPS (from the CUPS doc) is lpadmin, in any case, so not sure what lp is all about. In fact, the 'lp' group has ID=0, the same as the 'root' group.

    I fixed it by doing this:

    ~$ sudo chown root:lpadmin /dev/usb/lp0

    Then I noticed that /dev/lp0 and /dev/parport0 also had group=lp, so I also did this:

    ~$ sudo chown root:lpadmin /dev/lp*
    ~$ sudo chown root:lpadmin /dev/parport*

    Am I correct that this is an installation issue, or have I misdiagnosed?

  2. #2
    Join Date
    Mar 2010
    Location
    Lost in Contemplation
    Beans
    18
    Distro
    Ubuntu 9.10 Karmic Koala

    Re: Possible problem with /dev/*lp* in new installations

    I can add some more info to this thread. This issue is totally irrelevant as far as CUPS is concerned - please ignore the references to CUPS. I can now print through CUPS despite not being able to do something like

    echo Test > /dev/usblp0

    (CUPS works when the URI is parallel:/dev/usblp0, rather than usb:/dev/usblp0)

    However, I'm curious as to why this simple redirection to the device is disallowed until I change the permissions.

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