Rebuilding the existing kernel packages

To re-build the kernel modules and install the source packages follow these instructions. The kmod-fs-ext4 is used as an example:

1. Select the Kernel modules in the OpenWrt Configuration menu.

   

2. Navigate to Filesystems and select the kmod-fs-ext4 as M (modularized features). Note, all dependent kernel packages for kmod-fs-ext4 are selected automatically. 

   
3. Follow the original build flow to continue the setup and save the configuration for the firmware build process.
4. After the build process is complete, you can find the kernel packages under bin/ramips/packages/base/ (if the package you built is not there, you can also use the "find" command to locate where it is).
5. Copy all related kernel module packages to a USB drive.

6. Plug in the USB drive to LinkIt Smart 7688 development board and perform the opkg install command to install all necessary kernel packages from the USB drive. 

   root@mylinkit:/tmp/run/mountd/sda1# opkg install kmod*.ipk
   Installing kmod-crypto-core (3.18.23-1) to root...
   Installing kmod-crypto-hash (3.18.23-1) to root...
   Installing kmod-fs-ext4 (3.18.23-1) to root...
   Installing kmod-lib-crc16 (3.18.23-1) to root...
   Package kmod-lib-crc16 (3.18.23-1) installed in root is up to date.
   Configuring kmod-crypto-core.
   Configuring kmod-crypto-hash.
   Configuring kmod-lib-crc16.
   Configuring kmod-fs-ext4.  

   Note: if you simply install the kmod-fs-ext4, an error will occur like: 

   root@mylinkit:/tmp/run/mountd/sda1# opkg install kmod-fs-ext4_3.18.23-1_ramips_24kec.ipk
   Installing kmod-fs-ext4 (3.18.23-1) to root...
   Collected errors:
   * satisfy_dependencies_for: Cannot satisfy the following dependencies for kmod-fs-ext4:
   *      kmod-lib-crc16 *        kmod-crypto-hash *
   * opkg_install_cmd: Cannot install package kmod-fs-ext4.

   It's now obvious that additional kernel packages are also needed for kmod-fs-ext4 under bin/ramips/packages/base/ in Step 5.