The Linux pseudo random number generator (PRNG) is a special device that generates randomness from hardware interrupts (keyboard, mouse, disk/network I/O) and other operating system sources. This randomness is used mostly for encryption like SSL/TLS, but also has many other uses.
When this randomness is used up, you will encounter massive delays in the start and run time of flex.bi and other programs on your server, that's why we recommend using haveged.
Installing Haveged
Use the following command to create a yum repository:
su -c 'rpm -Uvh http://download.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-10.noarch.rpm'
Then install Haveged and start it:
yum install haveged systemctl enable haveged systemctl start haveged
To test the amount of available entropy, you can run the following command:
cat /proc/sys/kernel/random/entropy_avail