DOS filesystem (QNX Neutrino)


driver ... dos dos_options ... &

Runs on:



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

Use case-sensitive filename matching (forces long filenames). DOS/FAT is normally a case-preserving, case-insensitive filesystem.
Install a DOS codepage for mapping of locale 8.3 filenames. These names are used only when the corresponding (Unicode) long filename is absent (created pre-Win95) or has been disabled (using lfn=ignore) or for the volume label; specification of the appropriate locale will also allow portability of filenames created by fs-dos.so to older versions of DOS. Use the “chcp” native command on a DOS system to determine its active codepage. Supported values for mapping are:
mapping Description
cp437 DOS Latin US
cp850 DOS Latin-1
cp852 DOS Latin-2
cp866 DOS Cyrillic
cp1250 Windows Latin 2
cp1251 Windows Cyrillic
cp1252 Windows Latin 1
Set DOS/Windows compatibility mode. Certain versions of DOS implement minor individual peculiarities of the FAT on-disk format, although this is unlikely to affect any normal or typical filesystem client usage. The default is auto.
Specify how to handle the POSIX x-bit for executables:

The default is auto.

Set pre-reading of the FAT. Scanning the FAT 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:

The default is nonrmv.

Set the handling of the FAT32/FSI record (this contains a count of free clusters plus a hint at the next free cluster):

The default is lazy.

Set the owning group of all files to group. The default is 0 (root).
Specify what to do with files that have the DOS “hidden” attribute:

The default is show.

Specify what to do with long filenames:

The default is show.

Specify how to handle Windows shortcut files:
Enforce short (8.3) filenames. This option is valid only with lfn=ignore. By default, filename components beyond the 8.3 limit are silently ignored. For example, LONGFILENAME.TXT becomes LONGFILE.TXT.
Set POSIX check and emulation modes:

The default is emulate.

Specify how to display 8.3 filenames:

The default is lower.

Set the owner of all files to user. The default is 0 (root).
Apply this permission mask to all files. The default is 0 (all permissions). The mask argument is a numeric or symbolic umask, similar to what the chmod utility uses.

Note: Because getsubopt() interprets commas as separators between suboptions, you can specify only one symbolic mode at a time (e.g., u=rw, not u=rw,go=r). To work around this, specify more than one umask option (e.g., umask=u=rw umask=go=r).

Specify what to do with the DOS volume name:

The default is equals.

In addition, you can specify any of the filesystem options described for io-blk.so.


The fs-dos.so shared object lets you mount DOS filesystems (FAT12, FAT16, and FAT32) under QNX Neutrino.

The fs-dos.so shared object is automatically loaded by the devb-* drivers when mounting a DOS FAT filesystem.

Note: This filesystem uses UTF-8 encoding for presentation of its filenames; attempts to specify a filename not using UTF-8 encoding will fail (with an error of EILSEQ).

Summary of filesystem commands

The following table shows the shared objects and related commands for the filesystems:

Partition type Filesystem Shared object Initialize with: Check with:
1, 4, or 6 DOS fs-dos.so mkdosfs chkdosfs
7 Windows NTa fs-nt.so N/A N/A
11, 12, or 14 FAT32 fs-dos.so mkdosfs chkdosfs
77, 78, or 79 QNX 4 fs-qnx4.so dinit chkfsys
131 Linux (Ext2) fs-ext2.so N/A N/A
175 Apple Macintosh HFS or HFS Plusa fs-mac.so N/A N/A
177, 178, or 179 Power-Safe fs-qnx6.so mkqnx6fs chkqnx6fsb

a Read-only.

b Not usually necessary.

For more information, see the Filesystems chapter of the System Architecture guide.

See also:

chkdosfs, devb-*, fs-cd.so, fs-ext2.so, fs-mac.so, fs-nt.so, fs-qnx4.so, fs-qnx6.so, fs-udf.so, io-blk.so, mkdosfs, mount, umount

Filesystems chapter of System Architecture

QNX Neutrino User's Guide: