Before following the instructions in this section, user must have access to the switch console. User's terminal emulation software has to be configured with the following settings to ensure a successful console connection to the switch:

Baud rate: 115200
Data bits: 8
Stop bits: 1

Modifying U-Boot Parameters

U-Boot (Universal Boot Loader) is an open source, primary boot loader for embedded devices. U-boot is used to package the instructions to boot the operating system kernel of a device. The following example shows the auto boot-up sequence:

U-Boot 1.3.0 (Sep 8 2014 - 16:39:03) 
CPU:   8541, Version: 1.1, (0x80720011)
Core:  E500, Version: 2.4, (0x80200020)
Clock Configuration:
       CPU: 825 MHz, CCB: 330 MHz,
       DDR: 165 MHz, LBC:  41 MHz
L1:    D-cache 32 kB enabled
       I-cache 32 kB enabled
I2C:   ready
DRAM:  Initializing
initdram robin1
initdram robin2
robin before CFG_READ_SPD
robin after CFG_READ_SPD
initdram robin3
    DDR: 512 MB
FLASH: 32 MB
L2 cache 256KB: enabled
In:    serial
Out:   serial
Err:   serial
Net:   TSEC0, TSEC1
IDE:   Bus 0: OK
  Device 0: Model: CF 512MB Firm: 20060911 Ser#: TSS25016070309051750
            Type: Hard Disk
            Capacity: 495.1 MB = 0.4 GB (1014048 x 512)
Hit any key to stop autoboot:  5

To modify the baud rate or other boot parameters, interrupt the boot sequence by hitting any key during auto boot. Once the boot sequence is interrupted, user is at the U-boot shell.

Do not interrupt the default auto boot sequence unless the file system is being fixed or the console port settings are being changed.

The most common commands in U-Boot are:

help - Get command line help.
printenv - Show all environment variables. The U-Boot environment is a block of memory kept on persistent storage and copied to RAM when U-Boot starts. It stores environment variables used to configure the system.
version - Show the U-Boot version.
setenv - Set an environment variable.
saveenv - Save the modification in the environment memory.

Use the set and save commands to reset the U-Boot environment variables. In the example below, the baud rate is set to 11520 with the setenv baudrate 115200 command.

=> set baudrate 115200
=> save        
Saving Environment to Flash...
Un-Protected 1 sectors
Erasing Flash...
. done
Erased 1 sectors
Writing to Flash... done
Protected 1 sectors
=> reset

PicOS switches do support Linux shutdown command. To shut down a switch, after running the “sudo shutdown -h now" command, disconnect the power supply.

PICOS-4.4.4_Configuration_Guide

Boot Process and U-Boot Environment

Modifying U-Boot Parameters