8.2 Using an NFS-Mounted Root Filesystem to Write a Filesystem Image to Flash

Though we will discuss the setup and configuration of the NFS server on the host for providing a root filesystem to a target in detail in Chapter 9, let's take a look at how this configuration can be useful at this stage.

The use of an NFS-mounted root filesystem during early development stages simplifies the development process by allowing quick modification of the files used by the target. Later, the target needs to have a filesystem stored in its flash in order to be self-hosting. Though some bootloaders can be used to copy images to flash, it is also possible to use the MTD utilities running on the target to copy files available on the NFS-mounted root filesystem to flash. To do so, copy the designated filesystem image to the directory containing the NFS-mounted target root filesystem, boot the target, and use MTD commands on the target to copy the filesystem image to flash.

To copy an initial RAM disk image to your target's flash, for example, first configure your target to mount its root filesystem from a directory exported by your host using NFS. On your host, copy the filesystem image to the directory exported to your target. Though the filesystem image is not physically on your target, it will be visible on its root filesystem once the kernel mounts it using NFS at startup. Now, boot your target and use the MTD utilities on your target to copy the filesystem image from the NFS-mounted root filesystem to the appropriate flash device entry in your target's /dev directory.