U-boot environment: Difference between revisions

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On the SPI flash U-boot has both the U-boot application and the U-boot environment.  Our default build has 8KB of environment which can be used for variables and boot scripts.  These commands are relevant to manipulating the environment:
The eMMC flash contains both the U-Boot executable binary and U-Boot environment.  Our default build has 2 MiB of environment space which can be used for variables and boot scripts.  The following commands are examples of how to manipulate the U-Boot environment:


<source lang=bash>
<source lang=bash>
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env run hellocmd;
env run hellocmd;


# Commit env changes to the spi flash
# Commit environment changes to the SPI flash
# Otherwise changes are lost
# Otherwise changes are lost
env save
env save


# Restore env to default
# Restore environment to default
env default -a
env default -a


# Remove a variable
# Remove a variable
env delete emmcboot
env delete emmcboot
</source>
For a production environment the best option for setting depends on the number of units.  For a smaller number of units it may be simplest to update any required commands by hand.  For example, a custom cmdline option like "debug":
<source lang=bash>
env set cmdline_append 'console=ttymxc0,115200 ro init=/sbin/init debug'
env save
</source>
</source>

Latest revision as of 13:17, 27 September 2018

The eMMC flash contains both the U-Boot executable binary and U-Boot environment. Our default build has 2 MiB of environment space which can be used for variables and boot scripts. The following commands are examples of how to manipulate the U-Boot environment: 

# Print all environment variables
env print -a

# Sets the variable bootdelay to 5 seconds
env set bootdelay 5;

# Variables can also contain commands
env set hellocmd 'led red on; echo Hello world; led green on;'

# Execute commands saved in a variable
env run hellocmd;

# Commit environment changes to the SPI flash
# Otherwise changes are lost
env save

# Restore environment to default
env default -a

# Remove a variable
env delete emmcboot
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