Provided by: sg3-utils_1.17-2_i386 bug


       sg_prevent  -  invoke  SCSI  PREVENT  ALLOW MEDIUM REMOVAL command on a


       sg_prevent [--allow] [--help] [--prevent=<n>]  [--verbose]  [--version]


       Sends  a  SCSI  PREVENT ALLOW MEDIUM REMOVAL command to the given Linux
       SCSI device. The default action of this utility is to  allow  the  user
       and  the SCSI command START STOP UNIT (see sg_start) to remove or eject
       the medium from a drive. Typical examples are a removable disk, a  tape
       or  a  cd/dvd  drive.  The  definition  of the "prevent" codes for this
       command differ between disks and tapes (covered by  SPC-3)  and  cd/dvd
       drives  (covered  by  MMC-4). At the time of writing there are moves to
       remove these differences.  The "prevent codes" described here are  from
       MMC-4 which seems to be close to the proposed merged definition.

       --allow | -a
              allow medium removal. This is equivalent to setting the argument
              to ’--prevent’ to 2. Cannot  be  used  with  ’--prevent’  option
              (i.e.  use  no  options  (hence prevent removal), this option or

       --help | -h
              output the usage message then exit.

       --prevent=<n> | -p <n>
              prevent codes: 0 allows removal, 1 prevents removal (default), 2
              allows  persistent  removal while 3 prevents persistent removal.
              "Persistent" in this context means  that  the  initiator  (port)
              that  successfully  uses  code 3 blocks other initiators (ports)
              from allowing removal.  A  "persistent  prevent"  state  can  be
              cleared by owner allowing persistent removal (code 2) or a power
              cycle (or anything that resets the device (lun)) or some special
              commands  (e.g.  various  service  actions of Persistent Reserve
              Out, see SPC-3).

       --verbose | -v
              increase the level of verbosity, (i.e. debug output).

       --version | -V
              print the version string and then exit.

       In some cases removable media can be ejected  by  an  application  (see
       sg_start  and its ’-loej’ option). Often a user with physical access to
       the drive can attempt to eject the media by pressing a  button  on  the


       Written by Douglas Gilbert.


       Report bugs to <dgilbert at interlog dot com>.


       Copyright © 2004 Douglas Gilbert
       This  software  is  distributed  under  a  FreeBSD license. There is NO
       warranty; not even for MERCHANTABILITY  or  FITNESS  FOR  A  PARTICULAR


       sg_start(sg3_utils), sg_persist(sg3_utils)