---
name: "sg_prevent"
section: "8"
platform: "linux"
package: "sg3_utils"
version: "1.49-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/sg_prevent"
---

# sg\_prevent(8)

send SCSI PREVENT ALLOW MEDIUM REMOVAL command

## NAME

sg\_prevent - send SCSI PREVENT ALLOW MEDIUM REMOVAL command

## SYNOPSIS

**sg\_prevent** \[*--allow*\] \[*--help*\] \[*--prevent=PC*\] \[*--verbose*\] \[*--version*\] *DEVICE*

## DESCRIPTION

Sends a SCSI PREVENT ALLOW MEDIUM REMOVAL command to *DEVICE*. The default action of this utility is to prevent the removing or ejecting of the medium from a drive. This is done by ignoring the SCSI START STOP UNIT command (see sg\_start) and ignoring the eject button on the drive when the user presses it. Drives that hold removable disks, tape cartridges or cd/dvd media typically implement this command. The definition of the "prevent" codes for this command differ between disks and tapes (covered by SBC-3 and SSC-3) and cd/dvd drives (covered by MMC-5). The "prevent codes" described here are from MMC-5.

## OPTIONS

Arguments to long options are mandatory for short options as well.

- **-a**, **--allow**

  allow medium removal. This is equivalent to setting to '--prevent=2'. Cannot be used with *--prevent=PC* option (i.e. either use no options (hence prevent removal), this option or *--prevent=PC*).

- **-h**, **--help**

  output the usage message then exit.

- **-p**, **--prevent**=*PC*

  where *PC* is a prevent code value. Defined values are: 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 the owner allowing persistent removal (code 2) or a power cycle (or anything that resets the device (LU)) or some special commands (e.g. various service actions of Persistent Reserve Out, see SPC-3).

- **-v**, **--verbose**

  increase the level of verbosity, (i.e. debug output).

- **-V**, **--version**

  print the version string and then exit.

## EXIT STATUS

The exit status of sg\_prevent is 0 when it is successful. Otherwise see the [sg3\_utils(8)](/sg3_utils/8.md) man page.

## AUTHORS

Written by Douglas Gilbert.

## REPORTING BUGS

Report bugs to \<dgilbert at interlog dot com\>.

## COPYRIGHT

Copyright © 2004-2012 Douglas Gilbert\
 This software is distributed under a BSD-2-Clause license. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

## SEE ALSO

**sg\_start(sg3\_utils), sg\_persist(sg3\_utils)**