haveged

Generate a random number

$ sudo haveged

$ sudo haveged [[-F|--Foreground]]

$ sudo haveged [[-f|--file]] [path/to/file]

$ sudo haveged [[-r|--run]] [runlevel]

$ sudo haveged [[-b|--buffer]] [buffersizeinKW]

$ sudo haveged [[-c|--command]] [command]

$ sudo haveged [[-d|--data]] [cachesizeinKW]

$ sudo haveged [[-n|--number]] [byteamount]

haveged [options]

-h, -?, --help
    Display help message and exit

-v, --verbose[=level]
    Set verbosity (0=quiet, 1=info (default), 2=verbose, 3=debug)

-w, --wlevel=bytes
    Wake-up threshold for writing to /dev/random (default 1024)

-d, --debug
    Foreground mode with max debug logging (-v 3 -f implied)

-f, --foreground
    Run in foreground, do not daemonize

-p, --pidfile=filename
    Write PID to specified file

-g, --generator=name
    Select generator: havege, hemu, havege128, rdrand (default: havege)

haveged is a lightweight userspace daemon that generates pseudo-random data using the HAVEGE algorithm and feeds it into the Linux kernel's entropy pool. It addresses low-entropy issues on systems like VMs, headless servers, or embedded devices where hardware RNGs are scarce.

The daemon monitors the available entropy via /proc/sys/kernel/random/entropy_avail. When levels drop below a configurable threshold (default 1024 bits), haveged writes high-quality random bytes to /dev/random, ensuring smooth cryptographic operations without blocking.

HAVEGE exploits processor cache timing variations for entropy, producing gigabytes of data per second without special hardware. It's daemonized by default but supports foreground mode for debugging. Widely used in distributions like Arch Linux and Gentoo for boot-time entropy boosting.

While effective, haveged provides pseudo-entropy; it's best paired with hardware sources for optimal security.

Generates pseudo-random data, not true hardware entropy. Use alongside hwrng if available. May slightly impact CPU on low-end systems.

systemctl enable --now haveged or haveged -w 2048 -v 1 &
Check entropy: cat /proc/sys/kernel/random/entropy_avail

Reads/writes /dev/random; monitors /proc/sys/kernel/random/entropy_avail; optional PID in /run/haveged.pid

Developed by Bill Cox starting 2008; initial release 2011. Incorporated HAVEGE from Philippe Biondi. Adopted in Gentoo (2012), Arch Linux; active maintenance for modern CPUs.

rngd(8), egd(8)