Kernel message through UART debugging port

By default, kernel message through UART debugging port is disabled since removing kernel message reduce the boot time a bit and most regular user do not have UART debugging port.

Fix up the booting parameters

1. Uncomment the line where ttyAML0,115200n8 is specified from the file /usr/share/flash-kernel/ubootenv.d/upstream/10-console. This line will enable the UART debugging port for the kernel message.

   $ cat /usr/share/flash-kernel/ubootenv.d/upstream/10-console
   # Default serial console
   # setenv console "ttyAML0,115200n8"
   \
   # Default TTY console
   setenv bootargs "${bootargs} console=tty1"
   

2. Remove quiet from the file /etc/default/flash-kernel.

   $ cat /etc/default/flash-kernel\
   LINUX_KERNEL_CMDLINE="root=UUID=6322eafd-5b4c-474d-83ee-77c7223ccbd9 rootwait ro quiet splash"\
   LINUX_KERNEL_CMDLINE_DEFAULTS=""
   

3. In order to apply the change to the boot script, run update-bootscript.

   $ sudo /usr/sbin/update-bootscript