# lowest\_entropy

**URL:** <https://community.netdata.cloud/t/lowest-entropy/2455>\
**Category:** Alerts\
**Created:** [January 25, 2022, 2:59pm UTC](https://community.netdata.cloud/t/lowest-entropy/2455 "2022-01-25T14:59:14Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Ancairon](https://yyz1.discourse-cdn.com/flex029/user_avatar/community.netdata.cloud/ancairon/32/1001_2.png) [@Ancairon](https://community.netdata.cloud/u/Ancairon)\
**Post date:** [January 25, 2022, 2:59pm UTC](https://community.netdata.cloud/t/lowest-entropy/2455/1 "2022-01-25T14:59:14Z")

</div>

# lowest\_entropy

## OS: Linux

This alert presents the minimum amount of entropy in the kernel entropy pool in the last 5 minutes.

Low entropy can lead to a reduction in the quality of random numbers produced by `/dev/random`and `/dev/urandom`.

The Netdata Agent checks for the minimum entropy value in the last 5 minutes. The alert gets raised into warning if the value \< 100, and cleared if the value \> 200.

For further information on how our alerts are calculated, please have a look at our [Documentation](https://learn.netdata.cloud/docs/agent/health/reference#expressions).

> **What is entropy and why do we need it?**
>
> Entropy is similar to “randomness”. A Linux system gathers “real” random numbers by keeping an eye on different events: network activity, hard drive rotation speeds, hardware random number  
> generator (if available), key-clicks, and so on. It feeds those to the kernel entropy pool, which is  
> used by `/dev/random`.[1](https://unixhealthcheck.com/blog?id=472)
> 
> Encryption and cryptography applications require random numbers to operate. A function or an  
> algorithm that produces numbers -_that seem to be random_- is very predictable, if you know what function is used.
> 
> In real life, we use our surroundings and our thoughts to produce truly random numbers. A computer can’t really do this by itself, so it gathers numbers from a lot of sources. For example, it can get the CO2 levels in a room from a sensor on the system and use that as a random number.
> 
> This way all the values are random and there is no pattern to be found among them.

For further information, please have a look at the _References and Sources_ section.

> **References and Sources**
>
> 1. [Entropy](https://unixhealthcheck.com/blog?id=472)
> 2. [rng-tools](https://github.com/nhorman/rng-tools)
> 3. [How to add more entropy to improve cryptographic randomness on Linux](https://www.techrepublic.com/article/how-to-add-more-entropy-to-improve-cryptographic-randomness-on-linux/)
> 4. [Haveged Installation - Archlinux Wiki](https://wiki.archlinux.org/title/Haveged#Installation)

### Troubleshooting Section

The best tool to troubleshoot the lowest entropy alert is with `rng-tools`. If `rng-tools` are not  
available for your platform, or you run into trouble, you can use the tool `haveged` as an alternative.

> **Install and setup rng-tools**
>
> `rng-tools` is a random number generator daemon.  
> It monitors a set of entropy sources, and supplies entropy from them to the system kernel’s /dev/random machinery.[2](https://github.com/nhorman/rng-tools)
> 
> ### Installation
> 
> ### Debian-based platforms
> 
> ```auto
> root@netdata~ # sudo apt-get update
> root@netdata~ # sudo apt-get install rng-tools
> 
> ```
> 
> ### RHEL/Fedora/CentOS machines
> 
> 1. Change to the root account;
> 
> ```auto
> root@netdata~ # su
> 
> ```
> 
> 1. And then install;
> 
> ```auto
> root@netdata~ # yum install rng-tools
> 
> ```
> 
> ### After the Installation
> 
> You can run the service using the following command;
> 
> ```auto
> root@netdata~ # service rngd start
> 
> ```
> 
> And also you can check the daemon status using the following command;
> 
> ```auto
> root@netdata~ # service rngd status
> 
> ```

> **Install Haveged**
>
> Ideally, a system with high entropy demands should have a hardware device to generate random  
> numbers. For example, a TPM is such a device. However, there are also several software-only options you may install, like `haveged` [(_read more_)](https://wiki.archlinux.org/title/Haveged#Installation).
> 
> ### Installation
> 
> ### Debian-based platforms
> 
> 1. To install `haveged`, run:
> 
> 2. Set `haveged` up to start at boot with the command `sudo update-rc.d haveged defaults`.[3](https://www.techrepublic.com/article/how-to-add-more-entropy-to-improve-cryptographic-randomness-on-linux/) 
> 
> ### RHEL/Fedora/CentOS machines
> 
> 1. Change to the root account:
> 
> 2. Install `haveged`:
> 
> 3. Set `haveged` to start at boot with the command `chkconfig haveged on`.[3](https://www.techrepublic.com/article/how-to-add-more-entropy-to-improve-cryptographic-randomness-on-linux/)