Step-by-step – Build Kernel Ubuntu 21.04 Guide

Configuring

5. 5. Configuring Kernel

   So now to Configure Ubuntu Linux Custom Kernel
   First, access the Kernel Source with::

   cd linux*

   Then copy the current Configuration File into the New Kernel Source:

   sudo find /boot/ \( -iname "*config*" -a -iname "*`uname -r`*" \) -exec cp -i -t ./ {} \;

   mv *`uname -r`* .config

   This mystics because the default Configuration File may have a variable composition including “config” and the Kernel Version.
   In case of a Chrooted System instead you may look up the available Kernels with:

   ls /boot | grep config

   The grep Command refine the output List showing only the entries Matching the Keyword.
   Again fix the Configuration File editing it with nano and commenting out like:

   sudo nano .config

   Use Ctrl+w to search for “CONFIG_SYSTEM_TRUSTED_KEYS” on nano.
   And comment out the Line like:

   #CONFIG_SYSTEM_TRUSTED_KEYS

   Or else try to Set it like:

   CONFIG_SYSTEM_TRUSTED_KEYS=""

   Ctrl+x to Save & Exit.
   Else to reconfigure the Kernel use:

   sudo make menuconfig

   For instructions see: How to Configure a Build Kernel.