Caution: This version of this document is no longer maintained. For the latest documentation, see


QNX Neutrino microkernel and process manager (QNX Neutrino)


procnto* [-a d|e|s] [-c] [-e n|o] [-F number] [-fe]
         [-h] [-H size] [-mmemmgr_configuration]  
         [-P priority] [-p] [-T timeout] [-u umask] [-v]

Runs on:



Disable alignment fault emulation. The procnto manager doesn't attempt to make misaligned memory accesses work; they'll cause a SIGBUS signal for the offending thread.
Enable alignment fault emulation. The procnto manager attempts to make misaligned memory accesses work, although they'll be slow. This isn't guaranteed to work; offending threads may still get a SIGBUS signal.
Use the system default for alignment faults. This behavior depends on your platform:
Prevent the adaptive partitioning scheduler from automatically running threads that receive events from interrupt handlers as critical.

Note: The -c option has an effect only if:
  • you're using Adaptive Partitioning
  • the thread receiving an event from an interrupt handler is running in a partition configured with a critical budget

The -c option was added in the QNX Neutrino Core OS 6.3.2. For more information, see the Adaptive Partitioning User's Guide.

-e n|o
Specify which value to use for EALREADY:

Note: The -e option was added in QNX Neutrino 6.4.0. The default is -eo; it will be -en in a later release.

For more information, see "Changes to EALREADY" in the entry for errno in the Neutrino Library Reference.

-F number
The maximum number of file descriptors that can be open at the same time. The minimum allowable value is 100. The default value is 1000, but might be constrained by the RLIMIT_NOFILE system resource.

Note: Sockets, named semaphores, message queues, channel IDs (chids), and connection IDs (coids) all use file descriptors.

To determine the current limit, use the ksh builtin command, ulimit, or call getrlimit() (see the Library Reference).

Force floating-point emulation. The default is to use floating-point hardware in the CPU if present, and to emulate it in software if the CPU has no FPU (see Use this option to simulate a system with no FPU.
Disable CPU halting in idle thread. Some CPU and supporting chipsets can lock up if the CPU halts when idle; you'll notice the need for the -h option right away because your system will lock up after booting.
-H size
Sets the initial heap size for procnto. If more memory is required for procnto, it's dynamically obtained; however, by setting a properly calculated value this option can speed up boot time, and reduce the amount of physical memory fragmentation.

The size parameter indicates the number of bytes to grow the heap in advance. You can postfix this value with a multiplier character, such as "k" (kilobyte) or "m" (megabyte). For example:

1m == 1024k == 0x100000

If the number is less than 1024 and it isn't postfixed by a multiplier character, it's assumed to be in kilobytes. The default value is 64 KB if the -H option isn't specified.

-m memmgr_configuration
The memmgr_configuration string is a sequence of characters that enable (or if preceded with a ~ character, disable) memory-manager aspects.

Note: The -m option was added in the QNX Neutrino Core OS 6.3.2. If you specify more than one -m option, procnto ignores all but the last one.

The configuration options are:

Enable backward compatibility (the default).

Note: See the release notes for the current behavior.

Disable backward compatibility.
Make munmap() act as if UNMAP_INIT_REQUIRED were specified (i.e. POSIX initialization of the page to all zeroes is required the next time the underlying physical memory is allocated). This is the default.
Make munmap() act as if UNMAP_INIT_OPTIONAL were specified (i.e. initialization of the underlying physical memory to zeroes on its next allocation is optional). See "Initializing allocated memory" in the Interprocess Communication (IPC) chapter of the System Architecture guide.
l ("el")
Lock all memory; act as if mlockall(MCL_CURRENT|MCL_FUTURE) were specified at the start of every program. For more information, see mlockall() in the in the Neutrino Library Reference.
Don't lock all memory (the default).
Superlock all memory; act as if ThreadCtl(_NTO_CTL_IO,0) were specified at the start of every program. This affects only the locking of memory; programs don't actually get I/O privileges.
Don't superlock all memory (the default).

Note: If you enable both l and L, the L option takes priority.

Turn on full allocation of high memory for all processes. This is mostly useful only for testing.
Make sure that all anonymous allocation occurs below the 4 GB mark (the default).
Enable variable page sizes (the default). This automatically allows for mapping to be performed with different page sizes to achieve better performance.
Disable variable page sizes.
Enable the PROT_EXEC flag for system-allocated threads (the default). This option allows gcc to generate code on the stack -- which it does when taking the address of a nested function (a GCC extension).
Turn off PROT_EXEC for system-allocated stacks, which increases security but disallows taking the address of nested functions. You can still do this on a case-by-case basis by doing an mprotect() call that turns on PROT_EXEC for the required stacks.

Note: The -m[~]x option was added in QNX Neutrino 6.4.0.

-P priority
Set the lower end of the range of privileged priorities to the given priority; the upper end of the range is 255. Only processes with an effective user ID of 0 (i.e. root) can use these priorities. Non-root (and root) processes can use priorities from 1 through priority - 1. The default value of priority is 64.
Disable kernel preemption. This prevents threads running in kernel space from being preempted by a higher-priority thread. This can be useful when debugging a system with a frequent source of high-priority interrupts.
-T timeout
Specify the number of seconds to wait for a close() to succeed in the event of a process termination. Previously, this timeout was hard coded to be 30 seconds. The current default is also 30 seconds; however, the -T timeout option let's you set this value.

When a process terminates, any outstanding connections are closed. This means that an _IO_CLOSE message is synthesized and sent to the resource manager responsible for that connection.

Because it is not guaranteed that the server will reply in a reasonable amount of time (i.e, a qnet node may be down), a TimerTimeout() call before the send guarantees that the termination process will proceed.

Note: The -T option was added in QNX Neutrino 6.4.0.

-u umask
Use the given umask when creating the entries in /proc/pid/as. If you don't specify this option, procnto uses a mask of 022. You can restrict access further, but this could break software that relies on being able to open entries in /proc.

Note: The -u option was added in QNX Neutrino 6.4.0.

Be verbose. Specifying more v characters increases the verbosity. If you specify this option, you'll get more useful information when a process is terminated by a signal.


The procnto system process contains the QNX Neutrino microkernel, process management, memory management and pathname management. It's required in all bootable images made using the mkifs utility. For more information, see the QNX Neutrino System Architecture guide.

Note: To determine the release version of the kernel on your system, use the uname -a command.

There are different versions of procnto for different processors (see the Board Support Package for your board for specific information):

PowerPC 400 series processors.
PowerPC 800 series processors.
PowerPC 900 series processors.
PowerPC 900 series SMP processors.
Power Book E processors.
Other supported PowerPC SMP processors, such as the 600 and 700 series.
Other supported PowerPC processors, such as the 600 and 700 series.
ARMv6 processors.
All other supported multicore processors.
All other supported processors.

There's also an instrumented version of each of the above (e.g. procnto-600-smp-instr) that you'll use for system analysis. For self-hosted Neutrino systems, the default microkernel is procnto-instr.

Note: If you're using an SMP version of procnto, you can use the appropriate startup-* command's -P option to specify the maximum number of CPUs to activate.

Starting in 6.3.0, procnto also manages named semaphores, which mqueue used to do (mqueue now manages named semaphores only if it detects that procnto isn't doing so). Named semaphores appear in the pathname space under /dev/sem. The sem_* client functions handle named semaphores; for more information, see the Neutrino Library Reference.


To disable preemption in kernel code:

procnto -p

See also:, mkifs, startup-*, uname

mlockall(), mmap(), munmap(), munmap_flags(), sem_close(), sem_getvalue(), sem_open(), sem_post(), sem_trywait(), sem_unlink(), sem_wait() in the Neutrino Library Reference