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QNX Software Development Platform
System Architecture
The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
Process Manager
The process manager is capable of creating multiple POSIX processes (each of which may contain multiple POSIX threads).
Pathname management
I/O resources aren't built into the microkernel, but are instead provided by resource manager processes that may be started dynamically at runtime. The procnto manager allows resource managers, through a standard API, to adopt a subset of the pathname space as a domain of authority to administer.
Symbolic prefixes
We've discussed prefixes that map to a resource manager. A second form of prefix, known as a symbolic prefix, is a simple string substitution for a matched prefix.

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.
  - 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 is capable of creating multiple POSIX processes (each of which may contain multiple POSIX threads).
    - Process management
      The first responsibility of procnto is to dynamically create new processes. These processes will then depend on procnto's other responsibilities of memory management and pathname management.
    - Memory management
      The virtual memory system implements the POSIX model for memory management along with some QNX OS extensions.
    - Memory accounting
    - Pathname management
      I/O resources aren't built into the microkernel, but are instead provided by resource manager processes that may be started dynamically at runtime. The procnto manager allows resource managers, through a standard API, to adopt a subset of the pathname space as a domain of authority to administer.
      - Resolving pathnames
        When a process opens a file, the POSIX-compliant open() library routine first sends the pathname to procnto, where the pathname is compared against the prefix tree to determine which resource managers should be sent the open() message.
      - Symbolic prefixes
        We've discussed prefixes that map to a resource manager. A second form of prefix, known as a symbolic prefix, is a simple string substitution for a matched prefix.
        Creating special device names
        You can also use symbolic prefixes to create special device names.
        Relative pathnames
        Pathnames need not start with slash. In such cases, the path is considered relative to the current working directory.
      - File descriptor namespace
        Once an I/O resource has been opened, a different namespace comes into play. The open() returns an integer referred to as a file descriptor (FD), which is used to direct all further I/O requests to that resource manager.
  - 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.
  - 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
- 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.

Symbolic prefixes

QNX SDP8.0System ArchitectureDeveloperUser

We've discussed prefixes that map to a resource manager. A second form of prefix, known as a symbolic prefix, is a simple string substitution for a matched prefix.

You create symbolic prefixes using the POSIX ln (link) command. This command is typically used to create hard or symbolic links on a filesystem by using the -s option. If you also specify the -P option, then a symbolic link is created in the in-memory prefix space of procnto.


Command	Description
ln -s `existing_file` `symbolic_link`	Create a filesystem symbolic link.
ln -Ps `existing_file` `symbolic_link`	Create a prefix tree symbolic link.

Note that a prefix tree symbolic link will always take precedence over a filesystem symbolic link.

For example, assume you're running on a machine that doesn't have a local filesystem. However, there's a filesystem on another machine available over NFS (mounted at /nfs_host) that you wish to access as /bin. You accomplish this using the following symbolic prefix:

ln -Ps /nfs_host/x86_64/bin  /bin

This will cause /bin to be mapped into /nfs_host/x86_64/bin. For example, /bin/ls will be replaced with the following: /nfs_host/x86_64/bin/ls

Page updated: May 17, 2024