Red Hat Enterprise Linux is well known to set defaults across the industry. For example, RHEL pushed systemd so hard that all other Linux distro adopted for good or bad reasons. Now Red Hat announced that KDE Plasma Workspaces (KDE) been deprecated from RHEL 7.6 and all future version of RHEL. [continue reading…]
Red Hat Enterprise Linux (RHEL) 7.5 released. This version includes updates and various improvements such as GNOME rebased to version 3.26, LibreOffice rebased to version 5.3, Support for libva (VA-API) added, GStreamer now supports mp3 and more. RHEL is one of the leading enterprise Linux distribution for both bare metal and cloud platform. It targeted toward the commercial users. RHEL works with x86-64, IBM System z, and other platforms. [continue reading…]
Linux/Unix sysadmins have a weird obsession with server uptime. There is a xkcd comic devoted to this subject where a good sysadmin is an unstoppable force that it stands between the forces of darkness and your cat blog’s servers.
Like uptime command but with the more impressive output. Recently I discovered another tool called uptimed that records statistics about a machine’s uptime. Let us see how to get uptime record statistics using uptimed and uprecords on Linux operating system. [continue reading…]
Fedora Linux version 26.0 has been released ( jump to download ) after many months of constant development and available for download in various media format. Fedora 26 is a free and open source operating system includes various new features such as GCC 7, Golang 1.8, Python 3.6, DNF 2.0, OpenSSL 1.1.0 and more. Fedora 26 runs on both ARM servers and desktop boards too. [continue reading…]
There is a serious vulnerability in sudo command that grants root access to anyone with a shell account. It works on SELinux enabled systems such as CentOS/RHEL and others too. A local user with privileges to execute commands via sudo could use this flaw to escalate their privileges to root. Patch your system as soon as possible. [continue reading…]
Recently I came across an excellent software called CoreFreq. It is a CPU monitoring software designed for 64-bits Processors w/ architectures Intel Atom, Core2, Nehalem, SandyBridge and superior, and AMD Family 0F. It runs on 64 bit Linux system. CoreFreq provides a framework to retrieve CPU data with a high degree of precision: [continue reading…]
Entropy is nothing but the measure of “randomness” in a sequence of bits. The PRNG ( pseudorandom number generator ) is a special device (e.g. /dev/random on Linux) to create randomness from server hardware activities. It uses interrupts generated from the keyboard, hard disk, mouse, network and other sources. The random number generator gathers environmental noise from device drivers and other sources into an entropy pool. The randomness usually used for security purposes like creating TLS/SSL keys and the quality source of random bits is critical. For example, OpenSSL APIs can use quality randomness to make your program cryptographically secure. However, a poor source of randomness could result in loss of security. In this post, I will cover haveged and rng-utils/rng-tools to generate random numbers and feed Linux random device for your virtual or dedicated Linux server.
Running out of entropy on server or VMs is common
To see available entropy on Linux, enter: $ cat /proc/sys/kernel/random/entropy_avail
Sample outputs:
I was suggested to look into the haveged project. The haveged software provides an easy-to-use, unpredictable random number generator based on an adaptation of the HAVEGE algorithm. Another suggested option was to use rng-tools/rng-utils to speed up entropy.
Finding out your current availability of entropy and quality of randomness
You need to use the rngtest command as follows. Install it from rng-tools without starting rng in background: $ sudo RUNLEVEL=1 apt-get install rng-tools
$ cat /dev/random | rngtest -c 1000
It is going to take forever to run last command due to low quality randomness. Let us see how to install haveged or rng-tools.
Option #1: Install haveged
Linux entropy source using the HAVEGE algorithm and can installed as follows:
Debian/Ubuntu Linux
Type the following apt-get command: $ sudo apt-get install haveged
Sample outputs:
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
libhavege1
The following NEW packages will be installed:
haveged libhavege1
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 49.8 kB of archives.
After this operation, 196 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://01.archive.ubuntu.com/ubuntu xenial/universe amd64 libhavege1 amd64 1.9.1-3 [21.8 kB]
Get:2 http://01.archive.ubuntu.com/ubuntu xenial/universe amd64 haveged amd64 1.9.1-3 [28.0 kB]
Fetched 49.8 kB in 0s (58.6 kB/s)
Selecting previously unselected package libhavege1:amd64.
(Reading database ... 233574 files and directories currently installed.)
Preparing to unpack .../libhavege1_1.9.1-3_amd64.deb ...
Unpacking libhavege1:amd64 (1.9.1-3) ...
Selecting previously unselected package haveged.
Preparing to unpack .../haveged_1.9.1-3_amd64.deb ...
Unpacking haveged (1.9.1-3) ...
Processing triggers for libc-bin (2.23-0ubuntu4) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for systemd (229-4ubuntu12) ...
Processing triggers for ureadahead (0.100.0-19) ...
ureadahead will be reprofiled on next reboot
Setting up libhavege1:amd64 (1.9.1-3) ...
Setting up haveged (1.9.1-3) ...
Processing triggers for libc-bin (2.23-0ubuntu4) ...
Processing triggers for systemd (229-4ubuntu12) ...
Processing triggers for ureadahead (0.100.0-19) ...
RHEL/CentOS Linux
First, turn on EPEL repo and type: $ sudo yum install epel-release
$ sudo yum install haveged
Sample outputs:
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: centos.excellmedia.net
* epel: epel.mirror.angkasa.id
* extras: centos.excellmedia.net
* updates: centos.excellmedia.net
Resolving Dependencies
--> Running transaction check
---> Package haveged.x86_64 0:1.9.1-1.el7 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
=================================================================================
Package Arch Version Repository Size
=================================================================================
Installing:
haveged x86_64 1.9.1-1.el7 epel 61 k
Transaction Summary
=================================================================================
Install 1 Package
Total download size: 61 k
Installed size: 181 k
Is this ok [y/d/N]: y
Downloading packages:
warning: /var/cache/yum/x86_64/7/epel/packages/haveged-1.9.1-1.el7.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID 352c64e5: NOKEY
Public key for haveged-1.9.1-1.el7.x86_64.rpm is not installed
haveged-1.9.1-1.el7.x86_64.rpm | 61 kB 00:00:00
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
Importing GPG key 0x352C64E5:
Userid : "Fedora EPEL (7) <epel@fedoraproject.org>"
Fingerprint: 91e9 7d7c 4a5e 96f1 7f3e 888f 6a2f aea2 352c 64e5
Package : epel-release-7-6.noarch (@extras)
From : /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
Is this ok [y/N]: y
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Installing : haveged-1.9.1-1.el7.x86_64 1/1
Verifying : haveged-1.9.1-1.el7.x86_64 1/1
Installed:
haveged.x86_64 0:1.9.1-1.el7
Complete!
That is all. Test it: $ cat /proc/sys/kernel/random/entropy_avail
$ cat /dev/random | rngtest -c 1000
$ haveged -n 2g -f - | dd of=/dev/null
Option #2: Install rng-utils/rng-tools
The rngd is hardware RNG entropy gatherer daemon. Type the following yum command on a CentOS/RHEL based system: $ sudo yum install -y rng-utils
Sample outputs:
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: centos.excellmedia.net
* epel: epel.mirror.angkasa.id
* extras: centos.excellmedia.net
* updates: centos.excellmedia.net
Resolving Dependencies
--> Running transaction check
---> Package rng-tools.x86_64 0:5-7.el7 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
=========================================================================
Package Arch Version Repository Size
=========================================================================
Installing:
rng-tools x86_64 5-7.el7 base 34 k
Transaction Summary
=========================================================================
Install 1 Package
Total download size: 34 k
Installed size: 68 k
Is this ok [y/d/N]: y
Downloading packages:
rng-tools-5-7.el7.x86_64.rpm | 34 kB 00:00
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Installing : rng-tools-5-7.el7.x86_64 1/1
Verifying : rng-tools-5-7.el7.x86_64 1/1
Installed:
rng-tools.x86_64 0:5-7.el7
Complete!
Debian / Ubuntu Linux users type the following apt-get command: $ sudo apt-get install rng-tools
Sample outputs:
[sudo] password for vivek:
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
rng-tools
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 21.9 kB of archives.
After this operation, 139 kB of additional disk space will be used.
Get:1 http://01.archive.ubuntu.com/ubuntu xenial/universe amd64 rng-tools amd64 5-0ubuntu3 [21.9 kB]
Fetched 21.9 kB in 0s (34.3 kB/s)
Selecting previously unselected package rng-tools.
(Reading database ... 233574 files and directories currently installed.)
Preparing to unpack .../rng-tools_5-0ubuntu3_amd64.deb ...
Unpacking rng-tools (5-0ubuntu3) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for systemd (229-4ubuntu12) ...
Processing triggers for ureadahead (0.100.0-19) ...
ureadahead will be reprofiled on next reboot
Setting up rng-tools (5-0ubuntu3) ...
Processing triggers for systemd (229-4ubuntu12) ...
Processing triggers for ureadahead (0.100.0-19) ...
That is all. Test it: $ cat /proc/sys/kernel/random/entropy_avail
$ cat /dev/random | rngtest -c 1000
Fig.01: Testing availability of entropy & quality of randomness on Linux
Examples
Now you should see speed up while using the following commands. To use perfect forward secrecy cipher suites, you must set up Diffie-Hellman parameters on the server side. To generate a strong DH group or GPG keys using CLI, run: $ openssl dhparam -out dhparams.pem 2048
OR $ openssl dhparam -out dhparams.pem 4096
OR $ openssl dhparam -out dhparams.pem -dsaparam 4096
Type the following command to generates a key pair that consists of a public and a private key, execute: $ gpg2 --gen-key
To generate a /root/keyfile for disk encryption with LUKS, enter: $ sudo haveged -n 2048 -f /root/keyfile
To generate random ASCII passwords of the length 16 characters, run: $ (haveged -n 1000 -f - 2>/dev/null | tr -cd '[:graph:]' | fold -w 16 && echo ) | head -1
To test the randomness of the generated data with dieharder test suite (use ‘apt-get install dieharder‘ to use dieharder on Debian/Ubuntu Linux): $ haveged -n 0 | dieharder -g 200 -a
Sample outputs:
Two factor authentication is increasingly becoming a strongly recommended way of protecting user accounts in web applications from attackers by requiring a second method of authentication in addition to the standard username and password pair.
Although two factor authentication can encompass a wide range of techniques like biometrics or smart cards, the most commonly deployed technique in web applications is the one time password. If you have used applications like Gmail, you are probably familiar with the one time password generated by the Google Authenticator app that’s available on iOS or Android devices.
The algorithm used for the one time password in the Google Authenticator app is known as the Time-based One-Time Password (TOTP) algorithm. The TOTP algorithm is a standard algorithm approved by the IETF in (RFC 6238) totp-rfc. [continue reading…]
Today I will be talking about ansible, a powerful configuration management solution written in python. There are many configuration management solutions available, all with pros and cons, ansible stands apart from many of them for its simplicity. What makes ansible different than many of the most popular configuration management systems is that its agent-less, no need to setup agents on every node you want to control. Plus, this has the benefit of being able to control you entire infrastructure from more than one place, if needed. That last point’s validity, of being a benefit, may be debatable but I find it as a positive in most cases. Enough talk, lets get started with Ansible installation and configuration on a RHEL/CentOS, and Debian/Ubuntu based systems. [continue reading…]
If you want to monitor network throughput on the command line interface, use nload application. It is a console application which monitors network traffic and bandwidth usage in real time. It visualizes the in and outgoing traffic using two graphs and provides additional info like total amount of transferred data and min/max network usage. [continue reading…]
