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User's Guide
The QNX OS User's Guide is intended for all users of a QNX OS system, from system administrators to end users.
Working with Filesystems
The QNX OS provides a variety of filesystems, so that you can easily access DOS, Linux, as well as native Power-Safe disks.
Mounting and unmounting filesystems

QNX Momentics IDE User's Guide
QNX Software Development Platform
- Quickstart Guide
- System Architecture
  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
- OS Components
  - Boot Optimization Guide
    The Boot Optimization Guide describes techniques you can use to reduce the time from your board's initial power on until you have a fully functional QNX system running on the board.
  - Building Embedded Systems
    The Building Embedded Systems guide is intended for developers who are developing or building BSPs for QNX OS embedded systems.
  - Customizing a BSP
    While QNX provides Board Support Packages (BSPs) for many common platforms and their individual variants, in some cases, you need a BSP for a board that QNX does not provide. If this is the case, you can modify a QNX BSP or develop your own.
  - High Availability Framework Developer's Guide
  - High-Performance Networking Stack (io-sock) User's Guide
    This guide contains instructions for implementing and using the QNX OS High-Performance Networking Stack and its manager, io-sock.
  - PCI Server User's Guide
  - QNX Helpers Developer's Guide
    These libraries provide QNX helpers, including helpers that assist with logging, string conversion, and number and type sizes.
  - SMMUMAN User's Guide
  - SPI Framework Technote
  - System Analysis Toolkit (SAT) User's Guide
  - Technotes
  - User's Guide
    The QNX OS User's Guide is intended for all users of a QNX OS system, from system administrators to end users.
    - Getting to Know the OS
      Welcome to the QNX OS!
    - Logging In, Logging Out, and Shutting Down
      QNX OS is a multiuser operating system; it lets multiple users log in and use the system simultaneously, and it protects them from each other through a system of resource ownership and permissions.
    - Managing User Accounts
      This chapter explains how user accounts work, how users can change their password by using the passwd utility, and how system administrators can use the passwd utility and edit account database files to create and maintain users' accounts.
    - Using the Command Line
      Like QNX 4, Unix, and DOS, the QNX OS is based on a command-line interface that you might want or need to use instead of the GUI.
    - Working with Files
      In a QNX OS system, almost everything is a file; devices, data, and even services are all typically represented as files. This lets you work with local and remote resources easily from the command line, or through any program that works with files.
    - Using Editors
      An editor is a utility designed to view and modify files.
    - Configuring Your Environment
      The Building Embedded Systems guide describes what happens when you boot your system, and what you can do to customize it. This chapter describes how you can customize the environment that you get when you log in, and then describes some of the setup you might need to do.
    - Writing Shell Scripts
      Shell scripting, at its most basic, is taking a series of commands you might type at a command line and putting them into a file, so you can reproduce them again at a later date, or run them repeatedly without having to type them over again.
    - Working with Filesystems
      The QNX OS provides a variety of filesystems, so that you can easily access DOS, Linux, as well as native Power-Safe disks.
      - Setting up, starting, and stopping a block filesystem
        When you launch a block device driver (devb-*), it detects the partitions on the block I/O devices. You can then issue mount commands to start the appropriate filesystems for various partitions.
      - Mounting and unmounting filesystems
      - Managing disk quotas
        For the Power-Safe (QNX6) filesystem, you can define disk quotas to limit how many file entries a user or group of users can create and how large these files can grow.
      - Image filesystem
        By an image, we refer to an OS image here, which is a file that contains the OS, your executables, and any data files that might be related to your programs, for use in an embedded system.
      - /dev/shmem RAM filesystem
        QNX OS provides a simple RAM-based filesystem that allows read/write files to be placed under /dev/shmem.
      - Power-Safe filesystem
        The Power-Safe filesystem, supported by the fs-qnx6.so shared object, is a reliable disk filesystem that can withstand power failures without losing or corrupting data.
      - QNX compressed filesystem
        The QNX compressed filesystem (QCFS) provides a read-only filesystem that supports the compression of files and metadata so that they take up less space.
      - DOS filesystem
        The DOS filesystem provides transparent access to DOS disks, so you can treat DOS filesystems as though they were QNX OS (POSIX) filesystems. This transparency lets processes operate on DOS files without any special knowledge or work on their part.
      - Linux Ext2 filesystem
        The Linux Ext2 filesystem provided in QNX OS provides transparent access to Linux disk partitions.
      - Flash filesystems
        The QNX OS flash filesystem drivers implement a POSIX-compatible filesystem on NOR flash memory devices.
      - NFS filesystem
        The Network File System (NFS) protocol is a TCP/IP application that supports networked filesystems. It provides transparent access to shared filesystems across networks.
      - Universal Disk Format (UDF) filesystem
        The Universal Disk Format (UDF) filesystem provides access to recordable media, such as CD, CD-R, CD-RW, and DVD. It's used for DVD video, but can also be used for backups to CD, and so on.
      - Linux Squash filesystem
        The Squash filesystem provides support for Linux Squash compressed read-only filesystems.
      - Troubleshooting
    - TCP/IP Networking
      The term TCP/IP implies two distinct protocols: TCP and IP. Since these protocols have been used so commonly together, TCP/IP has become a standard terminology in today's Internet. Essentially, TCP/IP refers to network communications where the TCP transport is used to deliver data across IP networks.
    - Backing Up Data
      No matter how reliable your hardware and electrical supply are, or how sure you are that you'll never accidentally erase all your work, it's just common sense to keep backups of your files. Backup strategies differ in ease of use, speed, robustness, and cost.
    - Securing Your System
      Now that more and more computers and other devices are hooked up to insecure networks, security has become a very important issue. The word security can have many meanings, but in a computer context, it generally means preventing unauthorized people from making your computer do things that you don't want it to do.
    - Fine-Tuning Your System
      This chapter describes how you can improve your system's performance.
    - Understanding System Limits
      Resources on a system tend to be finite (alas!), and some are more limited than others. This chapter describes some of the limits on a QNX OS system.
    - Examples
      This appendix includes samples of some of the files described in this guide.
    - Glossary
- Graphics
- Programming
- System Security Guide
  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.
- Utilities & Libraries
- Migrating to QNX OS 8.0
QNX Software in the Cloud
QNX Toolkit for Visual Studio Code
This User's Guide describes the QNX Toolkit for Visual Studio Code. The guide introduces you to the QNX Toolkit by explaining the QNX development environment and how to build, run, and debug your QNX OS applications and systems.
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation and explains how to obtain technical support.

Mounting and unmounting filesystems

QNX SDP8.0User's GuideUser

The following utilities work with filesystems:

mount: Mount a block-special device or remote filesystem.
umount: Unmount a device or filesystem.

For example, if a block device is attached to your system and the necessary block device (devb-*) driver is already running, you can mount a Power-Safe filesystem to access files on that device like this:

mount -t qnx6 /dev/hd0t177 /mnt

By default, filesystems are mounted as read-write if the physical media permit it. You can use the -r option for mount to mount the filesystem as read-only. The io-blk.so library also supports an ro option for mounting block I/O filesystems as read-only.

You can also use the -u option for mount to temporarily change the way the filesystem is mounted. For example, if a filesystem is usually mounted as read-only, and you need to remount it as read-write, you can update the mounting by specifying -uw. For example:

mount -uw /

To return to read-only mode, use the -ur options:

mount -ur /

Block device drivers can use io-blk.so to implicitly mount filesystem images that are stored as files on another filesystem owned by the same process. This is done through an implicit loopback mechanism handled internally by io-blk.so. Suppose you have a devb-* process that services a Power-Safe filesystem partition at /mnt/q6. You can then mount any filesystem type that's supported by the block driver and stored as an image file on that partition by doing:

mount -t type -o ... /mnt/q6/file.img /newmnt

By mounting file images in this way, you can treat them as applications or optional packages, which can be protected using QNX Trusted Disk. On other OSs, you have to take an extra step and create a loop device before you can mount a filesystem image.

If the image file is located on a foreign storage solution or serviced by a resource manager that's not based on a block device driver, then you have to use devb-loopback to wrap the image file with a block device driver before mounting it. This is done as follows:

devb-loopback fd=/mnt/q6/file.img ...
mount -t type -o ... /dev/lo0 /newmnt

You should use umount to unmount a read-write filesystem before removing or ejecting removable media.

See the Utilities Reference for details on usage and syntax.

Page updated: May 17, 2024