I understand that reads to
/dev/random may block, while reading
/dev/urandom is guaranteed not to block.
Where does the letter
u come into this? What does it signify?
Userspace? Unblocking? Micro?
Based on the initial wording of the question, there has been some debate over the usefulness of
/dev/urandom. The link Myths about /dev/urandom has been posted three times below, and is summarised in this answer to the question When to use /dev/random vs /dev/urandom.
/dev/randomwhich is blocking.
/dev/randomwas somehow better than
/dev/urandomis now long obsolete and for the vast majority of use cases,
/dev/urandomis now preferred.