# Raw /dev/random output for keymat [duplicate]

Noob question:

It is my understanding that the raw output from

1. non-blocking /dev/random (where the kernel's entropy_avail estimate is equal to or greater than the number of random bits required)

1. or properly-initialized /dev/urandom (i.e., after roughly 256 bits of entropy have been collected by the system)

can be used without further post-processing as strong keymat for long-term symmetric crypto keys.

The output is gathered thusly (for the symmetric key):

//output 256 bits of entropy in 64 hex digits
od -N 64 -x /dev/random


Is there any weakness in this method as I have been recently led to believe (with no justification other than 'it's common knowledge', supposedly), or is raw /dev/[u]random output usable for long-term (>10 year) keymat?

Edit: remove any reference to asymmetric crypto to make its own question.