haveged

Start haveged daemon

$ sudo haveged

$ sudo haveged -F

$ sudo haveged -f [path/to/file]

$ sudo haveged -r [runlevel]

$ sudo haveged -b [buffersizeinKW]

$ sudo haveged -d [cachesizeinKW]

$ sudo haveged -n [byteamount]

haveged [options]

haveged is a random number generator daemon that feeds the Linux kernel's entropy pool (/dev/random). It uses the HAVEGE (HArdware Volatile Entropy Gathering and Expansion) algorithm, which harvests entropy from CPU timing variations.
The daemon is particularly useful for:
- Headless servers lacking traditional entropy sources (keyboard, mouse)
- Virtual machines with limited hardware entropy
- Systems requiring high-throughput random number generation
- Preventing /dev/random blocking during cryptographic operations
haveged monitors the kernel entropy pool and automatically feeds it when levels drop.

-F, --Foreground

Run in foreground (don't daemonize)

Write random data to file instead of /dev/random

Set run level (0=run as daemon, 1=display results)

Collection buffer size in KiB words

Cache size in KiB words

Number of bytes to write to output

Write BYTES to /dev/random at a time

Verbosity level

Some security researchers debate HAVEGE's entropy quality on virtualized or modern CPUs with consistent timing. Consider using hardware RNG (rngd) when available. On modern kernels, /dev/random no longer blocks, reducing the need for haveged.

haveged was developed by Gary Wuertz based on the HAVEGE algorithm created by André Seznec and Nicolas Sendrier. It became popular for addressing entropy starvation on Linux servers and VMs.

rngd(8), random(4), getrandom(2)