nvram command

# To [p]rint all the variables stored in the NVRAM:
nvram -p

# To [p]rint all the variables stored in the NVRAM using [x]ML format:
nvram -xp

# To Modify the value of a firmware variable:
sudo nvram <name>="<value>"

# To [d]elete a firmware variable:
sudo nvram -d <name>

# To [c]lear all the firmware variables:
sudo nvram -c

# To Set a firmware variable from a specific [x]ML [f]ile:
sudo nvram -xf <path/to/file.xml>