Overview: startup parameters and environment variables of VFS

VFS program startup parameters

• -l <entry in fstab format>

  The startup parameter -l mounts the defined file system.

• -f <path to fstab file>

  The parameter -f mounts the file systems specified in the fstab file. If the UNMAP_ROMFS environment variable is not defined, the fstab file will be sought in the ROMFS image. If the UNMAP_ROMFS environment variable is defined, the fstab file will be sought in the file system defined through the ROOTFS environment variable.

Examples of using VFS program startup parameters

Environment variables of the VFS program

• UNMAP_ROMFS

  If the UNMAP_ROMFS environment variable is defined, the ROMFS image will be deleted from memory. This helps conserve memory. When using the startup parameter -f, it also provides the capability to search for the fstab file in the file system defined through the ROOTFS environment variable instead of searching the ROMFS image.

  Example of using the UNMAP_ROMFS environment variable

• ROOTFS = <entry in fstab format>

  The ROOTFS environment variable mounts the defined file system to the root directory. When using the startup parameter -f, a combination of the ROOTFS and UNMAP_ROMFS environment variables provides the capability to search for the fstab file in the file system defined through the ROOTFS environment variable instead of searching the ROMFS image.

  Example of using the ROOTFS environment variable

• VFS_CLIENT_MAX_THREADS

  The VFS_CLIENT_MAX_THREADS environment variable redefines the SDK configuration parameter VFS_CLIENT_MAX_THREADS.

• _VFS_NETWORK_BACKEND=<VFS backend name>:<name of the IPC channel to the VFS process>

  The _VFS_NETWORK_BACKEND environment variable defines the VFS backend for working with the network stack. You can specify the name of the standard VFS backend: client (for a program that runs in the context of a client process), server (for a VFS program that runs in the context of a server process) or local, and the name of a custom VFS backend. If the local VFS backend is used, the name of the IPC channel is not specified (_VFS_NETWORK_BACKEND=local:). You can specify more than one IPC channel by separating them with a comma.

• _VFS_FILESYSTEM_BACKEND=<VFS backend name>:<name of the IPC channel to the VFS process>

  The _VFS_FILESYSTEM_BACKEND environment variable defines the VFS backend for working with file systems. The name of the VFS backend and the name of the IPC channel to the VFS process are defined the same way as they are defined in the _VFS_NETWORK_BACKEND environment variable.

Default values for startup parameters and environment variables of VFS

For the VfsRamFs executable file:

ROOTFS = ramdisk0,0 / ext4 0

VFS_FILESYSTEM_BACKEND = server:kl.VfsRamFs

For the VfsSdCardFs executable file:

ROOTFS = mmc0,0 / fat32 0

VFS_FILESYSTEM_BACKEND = server:kl.VfsSdCardFs

-l nodev /tmp ramfs 0

-l nodev /var ramfs 0

For the VfsNet executable file:

VFS_NETWORK_BACKEND = server:kl.VfsNet

VFS_FILESYSTEM_BACKEND = server:kl.VfsNet

-l devfs /dev devfs 0

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