www.kontron.com
CP6924-1-RA-A User Guide
46
4.3.2
Bootloader Shell Options
The boot process can be interrupted by entering the bootstopkey phrase “stop”. This will open a bootloader shell session.
Entering “?” provides a list of possible built-in commands, “printenv” provides a list of current environment settings. The
bootloader shell can be used to customize boot options and system startup by changing some of its environment variables.
A list of available environment variables and its description can be seen in the table below.
Table 4-3:
Bootloader Environment Variables
Name
Type
Description
baudrate
Var
Serial line baudrate
default: 115200
bootargs
Var
Default kernel arguments. (quiet postresult=0x${postresult}
${vram_kinfo})
bootcmd
Script
This variable defines a command string that is automatically executed
when the initial countdown is not interrupted.
This command is only executed when the variable bootdelay is also
defined!
bootcmdcli
Script
contains startup script which will drop to CLI and wait. This is used in
case that the system detects a rollback failed condition (rollback_ctl
= 1).
bootcmdflash
Script
contains the standard startup script for loading OS image from flash
partition command. This will load the Linux kernel and start it with a
INITRD type root file system.
bootcmdnet
Script
contains the standard startup script for loading OS image from net-
work.
bootcmdprd
Script
contains the standard startup script for use during board production.
bootcmdrecovery
Script
contains standard startup script for board firmware recovery in boot
firmware.
bootcmdrollback
Script
contains standard startup script for board firmware rollback from
backup partition after a CRC checksum error has been detected.
check bootsource
Script
check for user defined bootcmd/bootargs pair.
check rollback
Script
check whether previous rollback failed and drop into bootloader CLI.
bootdelay
Var
After reset, U-Boot will wait this number of seconds before it executes
the contents of the bootcmd variable. During this time a countdown is
printed, which can be interrupted by pressing any key.
Set this variable to 0 boots without delay. Be careful: depending on
the contents of your bootcmd variable, this can prevent you from
entering interactive commands again forever!
Set this variable to -1 to disable autoboot.
default: 3 for boot monitor, 10 for boot write-protected boot firm-
ware.
bootsource
Var
When the standard boot sequence is used, contains the boot source,
either flash, net, prd to select the respective boot sequence to acti-
vate. It is only used when bootcmd contains the default startup
script, which may be overridden by the user.
default: flash
bootstopkey
Var
Defines the key phrase that the user needs to type to drop into the
bootloader command line interface during startup.
not set – use string “stop” as bootstop key phrase (default)
<any> - use string <any> as bootstop key phrase
check bootsource
Script
Check for user defined bootsource extensions and execute them
check rollback
Script
Check for rollback prerequisites and start 'run rollback_flash' script
clear_config
Script
Erase config partition to restore factory defaults for Linux BSP set-
tings.
clear_env
Script
Erase U-Boot environment sectors.
disable_rollback
Var
0 – rollback when CRC check of kernel or rootfs fails (default)
1 – do not rollback
ethact
Var
Default network interface used by network commands (bootp, tftp-
boot et al)
default: ppc_4xx_eth0
