Mastering Linux with Tips and Tricks

All Mastering Linux with Tips and Tricks

Common Bash Error Messages on Linux and macOS (and How to Fix Them)

What common Bash errors mean and how to fix them: command not found, permission denied, bad substitution, ambiguous redirect, and more.

foobarupdated Aug 202657 examples

How To Calculate IP Subnets and Netmasks in Linux and macOS?

How to convert between CIDR prefixes and netmasks, and calculate network, broadcast, and usable host ranges with ipcalc, sipcalc, python3, and Bash.

ip -oupdated Aug 202617 examples

Find, Filter, and Count Text: How to become a badass with Grep

All you need to know to be efficient with grep for searching line matching a regular expression pattern.

curl -oupdated Dec 20211 example

What is the Best Way to Count Files in a Directory?

Learn how to count the number of files in a directory using the Linux command line ls, find, and a native bash shell solution with globs and arrays.

ls -aupdated Sep 20204 examples

What are the Differences Between Vi and Vim?

Vi vs Vim: A review of the main differences between the Vi/Ex POSIX standard and the Vim implementation.

updated Sep 2020

sudo: no tty present and no askpass program specified

Learn what is askpass and how to solve the 'sudo: no tty present and no askpass program specified' error when using sudo to execute a command.

%adminupdated Sep 20201 example

How To Format Date and Time in Linux, macOS, and Bash?

This guide covers how to format date and time in Linux, Mac, and the Bash shell. Includes how to do date shell operations like adding days or comparing dates.

calupdated Oct 202022 examples

What's New in Focal Fossa Ubuntu 20.04 LTS?

lsb_release -aupdated Sep 20206 examples

How To Do Advanced Math Calculation Using bc?

Learn how to use the GNU Linux bc command line to do math arithmetic and algebra with square root, sine, cosine, tangent, arctangent, bessel, and more.

echo "a=1;updated Sep 20208 examples

Disown a running shell process and reattach it to a new screen

This post cover the basics of shell jobs management and terminal screen sessions. It covers how to detach a running job from your current shell and how to attached it to a new TTY session.

bg [jobspecupdated Sep 20201 example

Redirecting a stdout to a file using sudo and tee

Learn how to address a permission denied error when trying to edit a file on Linux and work around some sudo issues. This post include a simple vim tips to save changes to a file with sudo right from your editor.

touchupdated Sep 20205 examples

sudo: sorry, you must have a tty to run sudo

Learn what is a tty and how to solve 'sudo: sorry, you must have a tty to run sudo' error when using ssh to execute a sudo remote command.

Defaults:myuserupdated Sep 20202 examples

Linux sysctl configuration and tuning script

Legacy post providing a custom script to auto-tune your Linux kernel and sysctl options based on your server specifications.

host=$(hostname)updated Sep 20201 example

Using losetup and dd to secure sensitive data

Legacy post on using dd and losetup to encrypt a block device and secure sensitive data.

dd if=/dev/zeroupdated Sep 20209 examples

Bind 9.5.0 - Patch dlz MySQL 5 for Auto Reconnect

Legacy post addressing connectivity issue from a Bind 9 server with the dlz MySQL driver to a MySQL 5 backend server. This post provides appropriate patch for the given software versions.

updated Sep 2020

Choosing a filesystem for your Linux/Unix server

Review of various filesystems available on Linux and how to choose one for your workstation or production server.

updated Sep 2020

Two common errors while starting Apache server on Linux

Legacy post discussing some common errors when starting or running an Apache server on Linux.

apachectl stopupdated Sep 20206 examples

How to Reload or Change your current Shell?

Learn the basic steps to reload your Linux shell to apply your recent configurations changes. This post cover the POSIX exec builtin command in Bash and the GNOME shell.

help execupdated Sep 20205 examples

Fine tuning a Linux Apache MySQL PHP (LAMP) server

Legacy post discussing how to tune a production system using Linux, Apache, MySQL, and PHP (aka LAMP).

sysctl [-n]updated Sep 20201 example

Removing ^M in imported Windows files

Learn how to quickly and easily handle files with newline and carriage return between linux, mac, and windows. This post will explain how to remove or replace the often annoying ^M character.

alias cvtCR="trupdated Sep 20202 examples

How to manage an idle ssh connection ?

Quick and simple tips on how to handle an idle remote ssh connection from your terminal.

updated Sep 2020

Raid 5 Monitoring on Dell Power Edge 2650 with afacli

Case study on monitoring a Raid 5 array on Dell PowerEdge 2650 with a PERC3/Di by using afacli on Debian.

wgetupdated Sep 20202 examples

Linux is the kernel Linus Torvalds first released in September 1991. What you actually run is a distribution built around it — the kernel, a GNU userland, an init system, and a package manager. Most of what follows holds on any of them, because the tools are the same whether you are on Debian, Ubuntu, RHEL, or Alpine.

This section covers the parts of that userland you end up fighting with: formatting dates and timezones, searching with grep, counting files in a directory without being lied to by ls, arbitrary-precision math with bc, subnets and CIDR netmasks, and tuning sysctl on a server that has run out of headroom.

It also covers the errors. command not found, Argument list too long, bad substitution, Killed — what they mean and what causes them — along with the two sudo failures that show up in every CI pipeline sooner or later: no tty present and sorry, you must have a tty to run sudo.