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518 lines
12 KiB
ReStructuredText
518 lines
12 KiB
ReStructuredText
.. SPDX-License-Identifier: CC-BY-SA-4.0
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.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)
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Filesystem Configuration
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========================
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By default, the In-Memory Filesystem (IMFS) is used as the base filesystem (also
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known as root filesystem). In order to save some memory for your application,
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you can disable the filesystem support with the
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:ref:`CONFIGURE_APPLICATION_DISABLE_FILESYSTEM` configuration option.
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Alternatively, you can strip down the features of the base filesystem with the
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:ref:`CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM` and
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:ref:`CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM` configuration options. These
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three configuration options are mutually exclusive. They are intended for an
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advanced application configuration.
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Features of the IMFS can be disabled and enabled with the following
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configuration options:
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* :ref:`CONFIGURE_IMFS_ENABLE_MKFIFO`
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* :ref:`CONFIGURE_IMFS_DISABLE_CHMOD`
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* :ref:`CONFIGURE_IMFS_DISABLE_CHOWN`
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* :ref:`CONFIGURE_IMFS_DISABLE_LINK`
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* :ref:`CONFIGURE_IMFS_DISABLE_MKNOD`
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* :ref:`CONFIGURE_IMFS_DISABLE_MKNOD_FILE`
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* :ref:`CONFIGURE_IMFS_DISABLE_MOUNT`
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* :ref:`CONFIGURE_IMFS_DISABLE_READDIR`
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* :ref:`CONFIGURE_IMFS_DISABLE_READLINK`
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* :ref:`CONFIGURE_IMFS_DISABLE_RENAME`
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* :ref:`CONFIGURE_IMFS_DISABLE_RMNOD`
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* :ref:`CONFIGURE_IMFS_DISABLE_SYMLINK`
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* :ref:`CONFIGURE_IMFS_DISABLE_UNMOUNT`
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* :ref:`CONFIGURE_IMFS_DISABLE_UTIME`
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.. index:: CONFIGURE_APPLICATION_DISABLE_FILESYSTEM
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.. _CONFIGURE_APPLICATION_DISABLE_FILESYSTEM:
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CONFIGURE_APPLICATION_DISABLE_FILESYSTEM
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----------------------------------------
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CONSTANT:
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``CONFIGURE_APPLICATION_DISABLE_FILESYSTEM``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default. If no other root file system configuration
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parameters are specified, the IMFS will be used as the root file system.
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DESCRIPTION:
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This configuration parameter is defined if the application dose not intend
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to use any kind of filesystem support. This include the device
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infrastructure necessary to support ``printf()``.
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NOTES:
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None.
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.. index:: CONFIGURE_IMFS_DISABLE_CHMOD
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.. _CONFIGURE_IMFS_DISABLE_CHMOD:
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CONFIGURE_IMFS_DISABLE_CHMOD
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----------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_CHMOD``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to change
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the mode is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_DISABLE_CHOWN
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.. _CONFIGURE_IMFS_DISABLE_CHOWN:
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CONFIGURE_IMFS_DISABLE_CHOWN
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----------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_CHOWN``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to change
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the owner is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_DISABLE_LINK
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.. _CONFIGURE_IMFS_DISABLE_LINK:
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CONFIGURE_IMFS_DISABLE_LINK
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---------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_LINK``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to create
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hard links is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_DISABLE_MKNOD
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.. _CONFIGURE_IMFS_DISABLE_MKNOD:
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CONFIGURE_IMFS_DISABLE_MKNOD
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----------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_MKNOD``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to make
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directories, devices, regular files and FIFOs is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_DISABLE_MKNOD_FILE
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.. _CONFIGURE_IMFS_DISABLE_MKNOD_FILE:
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CONFIGURE_IMFS_DISABLE_MKNOD_FILE
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---------------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_MKNOD_FILE``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to make
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regular files is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_DISABLE_MOUNT
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.. _CONFIGURE_IMFS_DISABLE_MOUNT:
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CONFIGURE_IMFS_DISABLE_MOUNT
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----------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_MOUNT``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to mount
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other file systems is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_DISABLE_READDIR
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.. _CONFIGURE_IMFS_DISABLE_READDIR:
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CONFIGURE_IMFS_DISABLE_READDIR
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------------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_READDIR``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to read a
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directory is disabled in the root IMFS. It is still possible to open nodes
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in a directory.
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.. index:: CONFIGURE_IMFS_DISABLE_READLINK
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.. _CONFIGURE_IMFS_DISABLE_READLINK:
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CONFIGURE_IMFS_DISABLE_READLINK
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-------------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_READLINK``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to read
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symbolic links is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_DISABLE_RENAME
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.. _CONFIGURE_IMFS_DISABLE_RENAME:
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CONFIGURE_IMFS_DISABLE_RENAME
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-----------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_RENAME``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to rename
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nodes is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_DISABLE_RMNOD
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.. _CONFIGURE_IMFS_DISABLE_RMNOD:
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CONFIGURE_IMFS_DISABLE_RMNOD
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----------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_RMNOD``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to remove
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nodes is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_DISABLE_SYMLINK
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.. _CONFIGURE_IMFS_DISABLE_SYMLINK:
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CONFIGURE_IMFS_DISABLE_SYMLINK
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------------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_SYMLINK``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to create
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symbolic links is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_DISABLE_UNMOUNT
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.. _CONFIGURE_IMFS_DISABLE_UNMOUNT:
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CONFIGURE_IMFS_DISABLE_UNMOUNT
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------------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_UNMOUNT``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to unmount
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file systems is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_DISABLE_UTIME
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.. _CONFIGURE_IMFS_DISABLE_UTIME:
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CONFIGURE_IMFS_DISABLE_UTIME
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----------------------------
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CONSTANT:
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``CONFIGURE_IMFS_DISABLE_UTIME``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to change
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times is disabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_ENABLE_MKFIFO
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.. _CONFIGURE_IMFS_ENABLE_MKFIFO:
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CONFIGURE_IMFS_ENABLE_MKFIFO
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----------------------------
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CONSTANT:
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``CONFIGURE_IMFS_ENABLE_MKFIFO``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the support to make FIFOs
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is enabled in the root IMFS.
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.. index:: CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK
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.. _CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK:
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CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK
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--------------------------------------
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CONSTANT:
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``CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Valid values for this configuration parameter are a power of two (2)
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between 16 and 512 inclusive. In other words, valid values are 16, 32, 64,
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128, 256,and 512.
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DEFAULT VALUE:
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The default IMFS block size is 128 bytes.
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DESCRIPTION:
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This configuration parameter specifies the block size for in-memory files
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managed by the IMFS. The configured block size has two impacts. The first
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is the average amount of unused memory in the last block of each file. For
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example, when the block size is 512, on average one-half of the last block
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of each file will remain unused and the memory is wasted. In contrast, when
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the block size is 16, the average unused memory per file is only 8
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bytes. However, it requires more allocations for the same size file and
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thus more overhead per block for the dynamic memory management.
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Second, the block size has an impact on the maximum size file that can be
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stored in the IMFS. With smaller block size, the maximum file size is
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correspondingly smaller. The following shows the maximum file size possible
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based on the configured block size:
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- when the block size is 16 bytes, the maximum file size is 1,328 bytes.
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- when the block size is 32 bytes, the maximum file size is 18,656 bytes.
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- when the block size is 64 bytes, the maximum file size is 279,488 bytes.
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- when the block size is 128 bytes, the maximum file size is 4,329,344 bytes.
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- when the block size is 256 bytes, the maximum file size is 68,173,568 bytes.
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- when the block size is 512 bytes, the maximum file size is 1,082,195,456
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bytes.
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.. index:: CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM
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.. _CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM:
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CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM
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--------------------------------------
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CONSTANT:
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``CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default. If no other root file system configuration
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parameters are specified, the IMFS will be used as the root file system.
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DESCRIPTION:
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This configuration parameter is defined if the application wishes to use
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the device-only filesytem as the root file system.
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NOTES:
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The device-only filesystem supports only device nodes and is smaller in
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executable code size than the full IMFS and miniIMFS.
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The devFS is comparable in functionality to the pseudo-filesystem name
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space provided before RTEMS release 4.5.0.
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.. index:: CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM
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.. _CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM:
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CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM
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-----------------------------------------
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CONSTANT:
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``CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM``
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DATA TYPE:
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Boolean feature macro.
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RANGE:
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Defined or undefined.
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DEFAULT VALUE:
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This is not defined by default.
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DESCRIPTION:
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In case this configuration option is defined, then the following
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configuration options will be defined as well
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- ``CONFIGURE_IMFS_DISABLE_CHMOD``,
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- ``CONFIGURE_IMFS_DISABLE_CHOWN``,
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- ``CONFIGURE_IMFS_DISABLE_UTIME``,
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- ``CONFIGURE_IMFS_DISABLE_LINK``,
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- ``CONFIGURE_IMFS_DISABLE_SYMLINK``,
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- ``CONFIGURE_IMFS_DISABLE_READLINK``,
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- ``CONFIGURE_IMFS_DISABLE_RENAME``, and
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- ``CONFIGURE_IMFS_DISABLE_UNMOUNT``.
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