Mounting file systems when VFS starts

When the VFS program starts, only the RAMFS file system is mounted to the root directory by default. If you need to mount other file systems, this can be done not only by calling the mount() function but also by setting the startup parameters and environment variables of the VFS program.

The ROMFS and squashfs file systems are intended for read-only operations. For this reason, you must specify the ro parameter to mount these file systems.

Using the startup parameter -l

One way to mount a file system is to set the startup parameter -l <entry in fstab format> for the VFS program.

In these examples, the devfs and ROMFS file systems will be mounted when the VFS program is started:

init.yaml.(in)

...

- name: VfsFirst

args:

- -l

- devfs /dev devfs 0

- -l

- romfs /etc romfs ro

...

CMakeLists.txt

...

set_target_properties (${vfs_ENTITY} PROPERTIES

EXTRA_ARGS

" - -l

- devfs /dev devfs 0

- -l

- romfs /etc romfs ro")

...

Using the fstab file from the ROMFS image

When building a solution, you can add the fstab file to the ROMFS image. This file can be used to mount file systems by setting the startup parameter -f <path to the fstab file> for the VFS program.

In these examples, the file systems defined via the fstab file that was added to the ROMFS image during the solution build will be mounted when the VFS program is started:

init.yaml.(in)

...

- name: VfsSecond

args:

- -f

- fstab

...

CMakeLists.txt

...

set_target_properties (${vfs_ENTITY} PROPERTIES

EXTRA_ARGS

" - -f

- fstab")

...

Using an "external" fstab file

If the fstab file resides in another file system instead of in the ROMFS image, you must set the following startup parameters and environment variables for the VFS program to enable use of this file:

1. ROOTFS. This environment variable mounts the file system containing the fstab file to the root directory.
2. UNMAP_ROMFS. If this environment variable is defined, the fstab file will be sought in the file system defined through the ROOTFS environment variable.
3. -f. This startup parameter is used to mount the file systems specified in the fstab file.

In these examples, the ext2 file system that should contain the fstab file at the path /etc/fstab will be mounted to the root directory when the VFS program starts:

init.yaml.(in)

...

- name: VfsThird

args:

- -f

- /etc/fstab

env:

ROOTFS: ramdisk0,0 / ext2 0

UNMAP_ROMFS: 1

...

CMakeLists.txt

...

set_target_properties (${vfs_ENTITY} PROPERTIES

EXTRA_ARGS

" - -f

- /etc/fstab"

EXTRA_ENV

" ROOTFS: ramdisk0,0 / ext2 0

UNMAP_ROMFS: 1")

...