best way to generate a random a key and vector in Linux

I want to generate a random key and vector in order to encrypt an image.

$ openssl enc -des -in [filename of the original file] -out [filename of the encrypted file]
-v -p -K [your key] -iv [initialization vector] -e

Is this the best way to generate a key and vector?

cat /dev/urandom | head -1 > randombytes.bin

xxd randombytes.bin | head -1