The following section defines those U-Boot configuration variables that can be configured using the kbuild build system configuration tools, such as menuconfig or xconfig. You can access the configuration user interfaces using

make menuconfig

This will build and run an ncurses-based configuration UI.

You can also build and run a graphical QT-based UI using

make xconfig

Configure a secure console

U-Boot allows you to configure console activation at boot. Go to General setup > Console settings in your configuration tool of choice and define the following configuration variables:

  • CONSOLE_DISABLE: This setting disables the U-Boot input and output consoles and performs a silent boot into Linux. You can then choose whether to optionally enable the console in one of two exclusive methods:

    • CONSOLE_ENABLE_GPIO: Use this setting to enable the console when the selected GPIO is high at boot.

    • CONSOLE_ENABLE_PASSPHRASE: Use this setting to enable the console when the correct passphrase is used at boot time.

      • CONSOLE_ENABLE_PASSPHRASE_KEY: This is the SHA-256 hash of the passphrase in binary form. You can generate it using the following command:

$ echo -n "password" | sha256sum
5e884898da28047151d0e56f8dc6292773603d0d6aabbdd62a11ef721d1542d8  -

See the Digi TrustFence for Yocto for further details.