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QNX 4 compatible filesystem support


driver ... qnx4 qnx4_options... &

Runs on:



Where driver is any of the devb-* drivers, and qnx4_options is one or more of the following, separated by commas:

When to pre-read the .bitmap file. Scanning the bitmap is required to return the count of free blocks. It also allows for improved write() performance by creating an in-memory summary of where free blocks might be located within the filesystem.

The value must be one of the following:

Allow persistent over-grown files; don't truncate them when they're closed. Certain file-write access patterns (e.g O_APPEND) are detected, and the file isn't shrunk back at the last close. This is useful for log files that you keep appending to, and so on.
Never embed inode details; always place in fixed-size .inodes.
Enable a more aggressive file-extent over-allocation heuristic.
Attempt to repair any file marked as “busy” on the filesystem (i.e. a file that was being grown or shrunk when the system was improperly shutdown). The default action is to return EBADFSYS to any attempt to open such a file; this option will instead truncate the file to its last-known valid size, unset the “busy” indicator, and allow access. This truncation may result in lost data and unused blocks marked as used in the bitmap, so run chkfsys later to ensure full filesystem consistency.

In addition, you can specify any of the filesystem options described for


The shared object provides support for QNX 4 filesystems. It's automatically loaded by the devb-* drivers when mounting a QNX 4 filesystem.


To enable support for long filenames (more than 48 characters) on an existing QNX 4 compatible filesystem, login as root and create an empty, read-only file named .longfilenames in the root directory of that filesystem.

To enable support for long filenames on a new QNX 4 filesystem, use the -N option to dinit.

See also:

devb-*,,,,,,,,, mount, umount

Filesystems chapter of System Architecture

QNX Neutrino User's Guide: