Provided by: sg3-utils_1.17-2_i386
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