linux – / dev / random权限被拒绝

The structure consists of a two-level cascaded sequence of pools coupled with 
CSPRNGs.
Each pool is a large group of bits which represents the current state of the 
random number generator. The CSPRNGs are currently based on SHA-1,but the 
kernel developers are considering a switch to SHA-3.

The kernel RNG produces two user-space output streams. One of these goes to 
/dev/urandom and also to the kernel itself; the latter is useful because there 
are uses for random numbers within the kernel. The other output stream goes to
/dev/random. The difference between the two is that /dev/random tries to estimate
how much entropy is coming into the system,and will throttle its output if there 
is insufficient entropy. By contrast,the /dev/urandom stream does not throttle
output,and if users consume all of the available entropy,the interface degrades
to a pure CSPRNG.

所以,我兴奋地试着进入并查看/ dev / random和/ dev / urandom中的内容.但它说,

root@ubuntu:/home/sunny# /dev/random
bash: /dev/random: Permission denied

root@ubuntu:/home/sunny# /dev/urandom
bash: /dev/urandom: Permission denied

但是,当我用“ls”命令检查时,我可以在/ dev中看到“随机”.
我想详细了解这一点.