io-fs-media Reference

Media filesystem interface

Synopsis:

io-fs-media [-a] [-b] [-cTYPE=num] [-ddriver,options] [-t] [-v]

Options:

-a
Start all built-in drivers. In this release, only tmp is built in.
-b
Don't run in the background. This setting is used for debugging.
-cTYPE=num
Set a cache size. The type of cache is specified by TYPE and can be one of:
  • attrs — number of attributes (default: 32)
  • bundles — number of 64 KB bundles (default: 2)
  • files — maximum number of files per filesystem (default: 1048576)
  • maps — number of extent mappings (default: 512)
  • mcache — maximum size of the meta cache (default: 16 KB)
  • meta — size of the metadata cache (default: 16 KB)
  • pages — number of 4 KB clusters (default: 256)
  • throngs — number of 1 MB throngs (default: 0)
  • wads — number of 256 KB wads (default: 0)
You can specify multiple -c options on the command line.
-ddriver,options
Start the specified driver with the specified options. The available drivers are:
  • tmp (built into io-fs-media)
  • MTP (iofs-pfs.so)
  • iPod (iofs-ipod.so)
Note: You should start each driver in its own process because io-fs-media is single-threaded.
-t
Print the built-in tables to stdout, then exit.
-v
Enable the verbose option for all mounted filesystems.

Description:

The io-fs-media filesystem interface makes distinct media devices and filesystems appear as POSIX-compliant filesystems under QNX Neutrino.

The io-fs-media service supports these media devices and filesystems:

RAM filesystem (tmp)
The tmp driver is statically linked to the io-fs-media binary and supports a temporary POSIX filesystem in RAM. For information on configuring this driver, see "Starting the RAM filesystem:".
MTP filesystem
The MTP driver supports access to files on MTP devices. This functionality is provided by the iofs-pfs.so library, which is loaded at runtime. A USB stack is required to use this driver. For information about starting and configuring the MTP driver, see "iofs-pfs.so Reference".
iPod filesystem
The iPod driver supports access to files on iPod devices. This functionality is provided by the iofs-ipod.so library, which is loaded at runtime. For information about starting and configuring this driver, see the iPod documentation shipped in the iPod download package.

Starting the RAM filesystem:

The tmp driver creates, in RAM, a temporary POSIX filesytem that exists for the duration of the io-fs-media process. You can configure this temporary filesystem by issuing io-fs-media commands with the -dtmp option followed by a comma-separated list defining one or more tmp driver options. The driver supports these options:

use
Print a usage message and then exit.
maxsize=size
The maximum size for the filesystem (in MB). You must provide a number followed by M to indicate the unit (e.g., maxsize=12M).
minsize=size
The minimum size for the filesystem (in MB). You must provide a number followed by M to indicate the unit (e.g., minsize=3M).
mount=path
Assign a mountpoint for the RAM filesystem. The default mountpoint is /fs/tmpfs.
noglob
Don't store the filesystem in global memory. This option is applicable on ARM targets only.

Example:

Suppose you issue this command to configure a temporary filesystem: 

# io-fs-media -d tmp,minsize=3M,maxsize=12M -cpages=4 -cbundles=0

The minsize option sets a minimum filesystem size of 3 MB, which is allocated at startup as contiguous memory. The memory allocation can increase up to the size specified by maxsize as needed. Memory allocated after startup is not necessarily contiguous.

With ARM targets, the behavior is different: at startup, memory is allocated contiguously up to the size in maxsize.