Mounting file systems when VFS starts
By default, the VFS component provides access to the following:
- RAMFS file system. RAMFS is mounted to the root directory by default.
- ROMFS object storage. The storage contains non-executable files (including configuration files) that are added to the solution image during the build. The ROMFS file system is not mounted by default. However, the storage can be accessed indirectly through the
-fargument, for example.
If you need to mount other file systems, this can be done either by using the mount() call after the VFS starts or immediately when the VFS starts by passing the following arguments and environment variables to it:
-l <entry in fstab format>The
-largument lets you mount the file system.-f <path to fstab file>The
-fargument lets you pass the file containing entries in fstab format for mounting file systems. The ROMFS storage will be searched for the file. If theUMNAP_ROMFSvariable is defined, the file system mounted using theROOTFSvariable will be searched for the file.UNMAP_ROMFSIf the
UNMAP_ROMFSvariable is defined, the ROMFS storage will be deleted. This helps conserve memory and change behavior when using the-fargument.ROOTFS = <entry in fstab format>The
ROOTFSvariable lets you mount a file system to the root directory. In combination with theUNMAP_ROMFSvariable and the-fargument, it lets you search for the fstab file in the mounted file system instead of in the ROMFS storage.
Example:
env.c
int main(int argc, char** argv)
{
/* The devfs and romfs file systems will be mounted for the Vfs1 entity. */
const char* Vfs1Args[] = {
"-l", "devfs /dev devfs 0",
"-l", "romfs /etc romfs 0"
};
ENV_REGISTER_ARGS("Vfs1", Vfs1Args);
/* The file systems defined through the /etc/dhcpcd.conf file located in the ROMFS storage will be mounted for the Vfs2 entity. */
const char* Vfs2Args[] = { "-f", "/etc/dhcpcd.conf" };
ENV_REGISTER_ARGS("Vfs2", Vfs2Args);
/* The ext2 file system containing the /etc/fstab file used for mounting additional file systems will be mounted to the root directory for the Vfs3 entity. The ROMFS storage will be deleted. */
const char* Vfs3Args[] = { "-f", "/etc/fstab" };
const char* Vfs3Envs[] = {
"ROOTFS=ramdisk0,0 / ext2 0",
"UNMAP_ROMFS=1"
};
ENV_REGISTER_PROGRAM_ENVIRONMENT("Vfs3", Vfs3Args, Vfs3Envs);
envServerRun();
return EXIT_SUCCESS;
}
Please also refer to the net_with_separate_vfs, net2_with_separate_vfs, multi_vfs_dhcpcd, multi_vfs_dns_client and multi_vfs_ntpd examples provided in KasperskyOS Community Edition.