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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.
System Architecture
The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
Filesystems
The QNX OS provides a rich variety of filesystems. Like most service-providing processes in the OS, these filesystems execute outside the kernel; applications use them by communicating via messages generated by the shared-library implementation of the POSIX API.
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
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
- System Architecture
  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
  - The Philosophy of the QNX OS
    The primary goal of the QNX OS is to deliver the open systems POSIX API in a robust, scalable form suitable for a wide range of systems—from tiny, resource-constrained embedded systems to high-end distributed computing environments. The OS supports several processor families, including x86 and ARM.
  - The QNX OS Microkernel
    The microkernel implements the core POSIX features used in embedded realtime systems, along with the fundamental QNX OS message-passing services.
  - Interprocess Communication (IPC)
    Interprocess Communication (IPC) plays a fundamental role in the transformation of the microkernel from an embedded realtime kernel into a full-scale POSIX operating system. As various service-providing processes are added to the microkernel, IPC is the glue that connects those components into a cohesive whole.
  - The Microkernel Instrumentation
    The microkernel (procnto-smp-instr) is equipped with a sophisticated tracing and profiling mechanism that lets you monitor your system's execution in real time. This instrumentation works on both single-CPU and SMP systems.
  - Process Manager
    The Process Manager can create and manage multiple POSIX processes, each of which may contain multiple POSIX threads.
  - Dynamic Linking
    In a typical system, a number of programs will be running. Each program relies on a number of functions, some of which will be standard C library functions, like printf(), malloc(), write(), etc.
  - Resource Managers
    To give the QNX OS a great degree of flexibility, to minimize the runtime memory requirements of the final system, and to cope with the wide variety of devices that may be found in a custom embedded system, the OS allows user-written processes to act as resource managers that can be started and stopped dynamically.
  - Filesystems
    The QNX OS provides a rich variety of filesystems. Like most service-providing processes in the OS, these filesystems execute outside the kernel; applications use them by communicating via messages generated by the shared-library implementation of the POSIX API.
    - Filesystems and pathname resolution
      You can seamlessly locate and connect to any service or filesystem that's been registered with the process manager. When a filesystem resource manager registers a mountpoint, the process manager creates an entry in the internal mount table for that mountpoint and its corresponding server ID (i.e., pid, chid identifiers).
    - Filesystem classes
    - Power-Safe filesystem
      The Power-Safe filesystem is a reliable disk filesystem that can withstand power failures without corruption.
    - 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 Trusted Disk
      QNX Trusted Disk (QTD) devices provide integrity protection of the underlying disk data in secure boot environments. They can extend the secure boot chain up to the core operating system filesystem that stores the critical binaries and configuration files.
    - Image filesystem
      Every QNX OS system image provides a simple read-only filesystem that presents the set of files built into the OS image.
    - DOS filesystem
      The DOS filesystem, fs-dos.so, provides transparent access to DOS disks, so you can treat DOS filesystems as though they were POSIX filesystems. This transparency allows processes to operate on DOS files without any special knowledge or work on their part.
    - Linux Ext2 filesystem
      The Linux Ext2 filesystem provides transparent access to Linux disk partitions.
    - UDF filesystem
    - FFS3 filesystem
      The Flash FileSystem version 3 (FFS3) drivers implement a POSIX-like filesystem on NOR flash memory devices. This filesystem is unique to QNX OS.
    - NFS filesystem
      The Network File System (NFS) allows a client workstation to perform transparent file access over a network. It allows a client workstation to operate on files that reside on a server across a variety of operating systems. Client file access calls are converted to NFS protocol requests, and are sent to the server over the network. The server receives the request, performs the actual filesystem operation, and sends a response back to the client.
    - Linux Squash filesystem
      The Linux Squash filesystem (squashfs) is a compressed read-only filesystem that allows you to compress data, inodes, and directories.
    - RAM filesystem
      Every QNX OS system also provides a simple RAM-based filesystem that allows read/write files to be placed under /dev/shmem.
    - Filesystem events
      Keeping up with a very live filesystem that changes often and quickly is a challenge for the programs that work with it. To help with this challenge, the QNX OS io-blk.so library and, thus, all devb-* drivers, support inotify_*() functions.
  - Character I/O
    A key requirement of any realtime operating system is high-performance character I/O.
  - Networking Architecture
    As with other service-providing processes in the QNX OS, the networking services execute outside the kernel. Developers are presented with a single unified interface, regardless of the configuration and number of networks involved.
  - TCP/IP Networking
    Our TCP/IP stack is included in the io-sock networking stack and uses the common FreeBSD API.
  - High Availability
    The term High Availability (HA) is commonly used in telecommunications and other industries to describe a system's ability to remain up and running without interruption for extended periods of time.
  - What is Real Time and Why Do I Need It?
    Real time is an often misunderstood—and misapplied—property of operating systems. This appendix provides a summary of some of the critical elements of realtime computing and discusses a few design considerations and benefits.
  - Glossary
- OS Components & Operations
- 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 Software in the Cloud enables developers to use the QNX OS in the Amazon cloud environment.
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^® Operating System (OS) applications and systems.
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.

QNX compressed filesystem

QNX SDP8.0System ArchitectureDeveloperUser

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. For information about ACL support in QNX OS, refer to the Working with Access Control Lists (ACLs) chapter in the Programmer's Guide.

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: August 11, 2025