Home
QNX Software Development Platform
OS Components
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.
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.

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.

QNX compressed filesystem

QNX SDP8.0User's GuideUser

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.

The fs-qcfs.so shared object supports the QCFS.

It includes the following features:

directory indexes
metadata compression
sparse file support
tail-end packing (fragments)
hard link support
a single or a double period entry (. or ..) in readdir()
real inode numbers
32-bit user or group IDs
file creation time
ACL support

For information on generating a QCFS image, see the mkqfs utility.

Supported compression algorithms

QCFS supports the following compression algorithms:

lz4hc: LZ4 high compression algorithm, which provides the best decompression speed at the cost of a lesser compression ratio.
zstd: Zstandard compression algorithm, which provides a good compression ratio and decryption speed.

Page updated: May 17, 2024