A Man and His Mutt - http://www.melonfire.com/community/columns/trog/article.php?id=98&page=1 A good guide to the mutt email client.
Advanced Bash Scripting Guide - http://www.tldp.org/LDP/abs/html/ An in-depth exploration of the art of shell scripting.
awk - http://www.grymoire.com/Unix/Awk.html A tutorial from Grymoire. Awk is an excellent filter and report writer. Many UNIX utilities generates rows and columns of information. AWK is an excellent tool for processing these rows and columns, and is easier to use AWK than most conventional programming languages.
AWK, GREP, SED tutorial - http://coewww.rutgers.edu/linux/lessons/lesson9/shell_script_tutorial.html A tutorial on, among other things, awk, grep and sed.
Awk Introduction Tutorial - 7 Awk Print Examples - http://www.thegeekstuff.com/2010/01/awk-introduction-tutorial-7-awk-print-examples/ This is the first article on the new awk tutorial series. We’ll be posting several articles on awk in the upcoming weeks that will cover all features of awk with practical examples. In this article, let us review the fundamental awk working methodology along with 7 practical awk print examples.
AWK Primer - http://www.vectorsite.net/tsawk.html The Awk text-processing programming language is a useful and simple tool for manipulating text. This document provides a quick Awk tutorial. It is also available in a downloadable archive, formatted in HTML, for reading on a tablet or other viewer.
awk & sed tutorials - http://www.theunixschool.com/p/awk-sed.html Tutorials from The UNIX School for the awk and *sed* commands.
More Great Linux Awk, Sed and Bash Tips and Tricks - https://www.linux.com/learn/docs/726140-more-great-linux-awk-sed-and-bash-tips-and-tricks/ Awk and Sed are powerful text processors that run circles around bloaty word processors. We're going to use them to customize the Bash prompt, add and remove line numbers, insert commas in long numbers, and perform all manner of experiments without endangering our source files.
Bash Keyboard Shortcuts - http://ss64.com/bash/syntax-keyboard.html You'll be glad you knew them.
Best Practices for UNIX chroot() operations - http://unixwiz.net/techtips/chroot-practices.html Systems exposed to the internet are heavily challenged to keep the bad guys out, and keeping up with the latest security patches is not always easy. So, the wise admin will attempt to institute systemic steps to limit the damage should a compromise occur, and one excellent method is the use of a chroot() jail.
Command Line Tutorials - Sed & Awk - https://quickleft.com/blog/command-line-tutorials-sed-awk/ We're going to take a look at two very important commands for your toolbox – "sed" and "awk". These two commands are pretty powerful, but as a result, their learning curve can be pretty steep. I'll provide you an outline to get you up to speed on sed and awk, but there's more to these commands than I have room here to cover. Fortunately, there's a ton of information on the internet about these commands, and I encourage you to read up on them once we're done.
Change runlevels in RHEL 7, How do I - https://access.redhat.com/solutions/2142121 This article describes the way runlevels are handled is updated in RHEL 7.
Crontab - Quick Reference - http://www.adminschoice.com/crontab-quick-reference "cron" is a Unix, solaris, Linux utility that allows tasks to be automatically run in the background at regular intervals by the cron daemon.
CTRL-ALT-DELETE Behavior Modification - http://www.cyberciti.biz/tips/linux-disable-the-ctrl-alt-del-shutdown.html Keep linux from rebooting in response to the three finger salute.
Explain Shell - https://explainshell.com/ This site contains 29761 parsed manpages from sections 1 and 8 found in Ubuntu's manpage repository. A lot of heuristics were used to extract the arguments of each program, and there are errors here and there, especially in manpages that have a non-standard layout. In other words, if you give this a bash command, it will explain what the command does.
Fedora Extra Packages for Enterprise Linux - https://fedoraproject.org/wiki/EPEL Extra Packages for Enterprise Linux (or EPEL) is a Fedora Special Interest Group that creates, maintains, and manages a high quality set of additional packages for Enterprise Linux, including, but not limited to, Red Hat Enterprise Linux (RHEL), CentOS and Scientific Linux (SL), Oracle Linux (OL).
Harping on ARP - http://lwn.net/Articles/45373/ One of the longer-running current discussions on linux-kernel (and linux-net, and netdev) was started on July 27, when Bas Bloemsaat pointed out a problem that he was having. The Linux implementation of ARP, it seems, it not working as he would like.
Icinga Blog - https://www.icinga.com/blog/ The official blog for Icinga2 monitoring software.
Linux eMail Server - Mail Transfer Agent (MTA) software - http://www.yolinux.com/TUTORIALS/LinuxTutorialMailMTA.html Internet mail is sent from the email client to the email server which routes it to the intended destination which will also be an email server. The protocol by which the email servers communicate is called SMTP (Simple Mail Transfer Protocol) and the email server software is known as the MTA or Mail Transfer Agent. This tutorial lists the popular MTA eMail server programs used, basic Sendmail email server configuration as well as Postfix email server configuration. Also listed are Mailing List programs and the RFC's (Request For Comments) on which the internet email standards are currently or eventually based.
Linux Man Pages - http://linux.die.net/man/ HTML versions of Linux Man Pages. If you don't know what these are, you probabably worry about viruses and windows updates every week.
Linux Newbie Guide by Stan, Peter and Marie Klima - unixguide.net/linux/ A great resource for those just starting out with Linux. LNAG and LAME have both helped me with some basic concepts in getting started with linux.
Performing Math Calculation in Bash - https://www.shell-tips.com/2010/06/14/performing-math-calculation-in-bash/ I use math in bash scripts a lot, from simple crontab reports to Icinga2 monitoring plugins… Here is few small examples on how to do some math in Bash with integers or float. Especially since math in bash might surprise you if you haven't already read this.
Procmail Strategies Against Spam - http://pm-lib.sourceforge.net/README.html Spam is a problem. This document contains a detailed analysis of various ways that Procmail can be used to combat spam.
Red Hat Enterprise Linux 7 System Administrator's Guide - https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/index.html The System Administrator's Guide documents relevant information regarding the deployment, configuration, and administration of Red Hat Enterprise Linux 7. It is oriented towards system administrators with a basic understanding of the system.
Regular Expressions .info - http://www.regular-expressions.info/ A regular expression (regex or regexp for short) is a special text string for describing a search pattern.
RPM How To - http://www.tldp.org/HOWTO/RPM-HOWTO/build-it.html Detailed steps on creating RPM files.
Rubular - http://rubular.com/ Rubular is a Ruby-based regular expression editor. It's a handy way to test regular expressions as you write them.
Rute user's Tutorial and Exposition - http://linuxcourse.rutgers.edu/rute/rute.html LINUX books assumed that anyone using LINUX was migrating from System V or BSD--systems that I had never heard of. It is a sensible adage to create, for others to share, the recipe that you would most like to have had. Indeed, I am not convinced that a single unifying text exists, even now, without this book. Even so, I give it to you desperately incomplete; but there is only so much one can explain in a single volume.
Sed - http://www.panix.com/~elflord/unix/sed.html This tutorial is meant as a brief introductory guide to sed that will help give the beginner a solid foundation regarding how sed works. It's worth noting that the tutorial also omits several commands, and will not bring you to sed enlightenment in itself.
Server Lab Linux Pages - http://www.serverlab.ca/category/tutorials/linux/administration-linux/ Server Lab has many articles covering Linux administration, database, network services, storage and file systems, and web servers.
Simple Awk Tutorial - http://www.hcs.harvard.edu/~dholland/computers/awk.html Harvard's simple awk tutorial.
Some VMware images - http://www.thoughtpolice.co.uk/vmware/ If you wish to try out several linux flavors without interruption to your current OS before you really install it, VMWare plus these images will do just that and bypass the pain of installing them in VMWare too!
SysVinit to Systemd Cheatsheet - https://fedoraproject.org/wiki/SysVinit_to_Systemd_Cheatsheet This is a document to help system administrators who need to understand what commands in systemd replace their old workflow in sysvinit. If you want general information on systemd, refer to systemd.
Using the Watchdog Timer in Linux - https://www.jann.cc/2013/02/02/linux_watchdog.html Covers use of the linux watchdog timer.
What is the difference between test, [ and [[ ? - http://mywiki.wooledge.org/BashFAQ/031 [ ("test" command) and [[ ("new test" command) are used to evaluate expressions. [[ works only in Bash, Zsh and the Korn shell, and is more powerful; [ and test are available in POSIX shells. Here are some examples.