For mLinux versions 4.0 or higher:

This command is in mLinux^™ 4.0 or higher for the u-Boot password feature, mts-ubpasswd.

U-Boot can only be accessed via the front USB port.

In order to access U-Boot commands, if there is a U-Boot password, you will be solicited for the password. If you do not successfully enter the password, the system will boot the mLinux OS. If you do not attempt to enter a U-Boot password, the system will boot normally.

The passwd command will still be available to set an mLinux password.

If mts-ubpasswd is invoked with [-u], it will set only the U-boot password.

If mts-ubpasswd is invoked without [-u] it will set both the mLinux administrator (mtadm) and U-boot password. U-Boot has no user-id.

The maximum length of the U-boot password is 29 characters.

Salt may be supplied.

mtcdt:$ sudo mts-ubpasswd --help
ubpasswd [-c] [-m] [-r] [-u] [-d] [-s salt] [password]
  -c        clear the U-Boot password
  -d        debug
  -m        means use the mac to generate the password 
  -r        returns true if U-Boot password
            is currently required
  -s        salt is user supplied salt
  -u        means u-boot only (not UNIX password)

The password is a user supplied password. A salt not supplied is generated. If a password is not supplied, it is generated. The password is generated using a hash algorithm from the Ethernet MAC address and the Device-ID (serial number).

Here is an example of setting the U-Boot password:

    mtcdt:$ sudo mts-ubpasswd -u 'RedWhiteBlue1993'
    salt: tq7QunBl3KMM7K5/n3v4pMwG2lQArnT9LTLU1P5z6BbStfxU9J4Do+RuUAVfa93t8LldIyGlUhBfOPdXjUvEV4FesXyp3Uh40lx0hQm5RyWYeNPy0Q6nMX6L+vUgQXVy
    uboot password hash: "87defd89a743a151499f74e83b4d7cd9dbceecc915aad60d9b67d381e7ad3e79"
    u-boot password is RedWhiteBlue1993
    + /usr/bin/u-boot setenv mtss tq7QunBl3KMM7K5/n3v4pMwG2lQArnT9LTLU1P5z6BbStfxU9J4Do+RuUAVfa93t8LldIyGlUhBfOPdXjUvEV4FesXyp3Uh40lx0hQm5RyWYeNPy0Q6nMX6L+vUgQXVy
    + /usr/bin/u-boot setenv mtsp 87defd89a743a151499f74e83b4d7cd9dbceecc915aad60d9b67d381e7ad3e79

    If you wish to remove the u-boot password (not recommended) perform the following commands:

    mtcdt:$ sudo mts-ubpasswd -c

If a key is pressed after U-Boot starts:

    U-Boot 2016.09.01 (May 25 2017 - 03:06:22 -0500)

    CPU: AT91SAM9G25
    Crystal frequency:       12 MHz
    CPU clock        :      400 MHz
    Master clock     :  133.333 MHz
           Watchdog enabled
    I2C:   ready
    DRAM:  256 MiB
    WARNING: Caches not enabled
    NAND:  256 MiB
    MMC:   mci: 0
    env_relocate_spec: crc1_ok=1 saved crc=0x139075a calculated crc=0x139075a flags=0
    env_relocate_spec: crc2_ok=1 saved crc=0x139075a calculated crc=0x139075a flags=0
    In:    serial
    Out:   serial
    Err:   serial
    vendor-id:  Multi-Tech Systems
    product-id: MTCDT-240L
    device-id:  P8704508
    hw-version: MTCDT-0.1
    mac-addr:   00:08:00:4a:00:07
    Net:   macb0
    Hit any key to stop autoboot:  0

    Enter password : ****************
    U-Boot>

The system will replace any characters typed with asterisks when the password is entered