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QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
Utilities & Libraries
Utilities Reference
U
umount
Unmount a device

QNX Momentics IDE User's Guide
This User's Guide describes version 8.0 of the Integrated Development Environment (IDE) that's part of the QNX Tool Suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
- Quickstart Guide
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  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
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  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX OS system and developers who want to create a QNX OS resource manager free from vulnerabilities.
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    These libraries provide QNX helpers, including helpers that assist with logging, string conversion, and number and type sizes.
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    The QNX Cryptography Library (qcrypto) is a flexible cryptography framework that allows you to choose which cryptography provider responds to requests on a per-process basis.
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      - ubus_ctrl
        USB Bus State Enable/Disable utility
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        Micro-embedded shell (QNX OS)
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        Control a USB DCD link
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        Get or set the file mode creation mask (POSIX)
      - umount
        Unmount a device
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- Migrating to QNX OS 8.0
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QNX Hypervisor User's Guide
This User's Guide explains the QNX hypervisor architecture and provides instructions for installing and running a QNX Hypervisor system, changing system components and configuration, and using hypervisor features such as virtual devices (vdevs).
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation, explains how to obtain technical support, and provides some information about licensing.

umount

QNX SDP8.0Utilities ReferenceUtilities

Unmount a device

Syntax:

umount [-fv] [-T type] path [path ...]

Runs on:

QNX OS

Options:

-f: Force an unmount, even if the device is busy.
-T type: Typed umount (not currently supported).
-v: Be verbose.
path: The root mountpoint to be unmounted.

Description:

This utility unmounts the devices that were mounted as the given paths.

If a device is busy (for example, if a file is open), umount fails. You can force the device to be unmounted by specifying the -f option.

In order to use this utility, your process needs to have the vfs/mount-blk (BLK_ABILITY_MOUNTVFS) custom ability enabled. For more information, see procmgr_ability() and procmgr_ability_lookup() in the C Library Reference.

Page updated: August 11, 2025