Linux Tips, Hacks, Tutorials, And Ideas In Blog
Linux Tips, Hacks, Tutorials, And Ideas In Blog
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.
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:
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.
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.
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.
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.
The nicstat command is top like utility for network interface card (NIC). It displays information and statistics about all your network card such as packets, kilobytes per second, average packet sizes and more. It works under Solaris and Linux operating systems.
In this post, I will explain how to install and use the nicstat command to find out stats about your NICs under Debian / Ubuntu / RHEL / CentOS Linux operating systems.
The iotop command is top like utility for disk I/O. It watches I/O usage information output by the Linux kernel (requires v2.6.20 or later) and displays a table of current I/O usage by processes or threads on the system. This post expalins how to install and use iotop to find out what’s stressing (or program names) on your hard drives under Linux operating systems.