# Generate a UUID
uuidgen

# using a string as a seed to produce the same UUID each time
echo -n "unique_string" | openssl dgst -sha256 | sed 's/.* //' | cut -c1-36

# dashes are part of the standard, so lets add them
echo -n "unique_string" | openssl dgst -sha256 | sed 's/.* //' | cut -c1-36| sed -E 's/(.{8})(.{4})(.{4})(.{4})(.{12})/\1-\2-\3-\4-\5/'

# using sha256sum (which is in busybox) - also removes the need for the first sed command
echo -n "unique_string" |sha256sum | cut -c1-36| sed -E 's/(.{8})(.{4})(.{4})(.{4})(.{12})/\1-\2-\3-\4-\5/'