How to improve your bash/sh shell script with ShellCheck lint script analysis tool

{Updated} ShellCheck is a static analysis tool for shell scripts. One can use it to finds bugs in your shell scripts. It is written in Haskell. You can find warnings and suggestions for bash/sh shell scripts with this tool. Let us see how to install and use ShellCheck on a Linux or Unix-like system to enhance your shell scripts, avoid errors and productivity.

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How to install VirtualBox on Ubuntu 20.04 Linux LTS

How do I install VirtualBox application on Ubuntu 20.04 Linux LTS system?

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How to install MySQL server on Ubuntu 20.04 LTS Linux

How do I install MySQL server 8.0 on Ubuntu 20.04 LTS Linux server? How can I add a new MySQL user and database on the newly set up Ubuntu server?

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How To check LXD container BTRFS disk usage on Linux

Here is a quick and dirty shell script I put to check LXD container size and how much space they are taking on the BTRFS subvolume. Naturally, you must run the script as a root user, and LXD must be configured with BTRFS storage backend on Linux operating systems. See how to set up and install LXD on Ubuntu 20.04 LTS using the apt command

How to check TLS/SSL certificate expiration date from command-line

How do I check the TLS/SSL certificate expiration date from my Linux or Unix shell prompt? How can I find the TLS certificate expiry date from Linux and Unix shell scripts?

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Linux / UNIX Desktop Fun: Terminal ASCII Aquarium

{Updated} You can now enjoy mysteries of the sea from the safety of your own terminal using ASCIIQuarium. It is an aquarium/sea animation in ASCII art created using perl.

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How to delete container with lxc (LXD) command on Linux

Want to delete LXD based container with lxc command on Linux? Try these simple tips. To delete LXD instances/container and snapshots, we use the lxc delete command. However, the container/instance must be stopped, and all snapshots must be removed before removing the Linux container with the lxc command.

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How to show dropped packets per interface on Linux

How do I display dropped packets per interface on Linux operating systems from the command line option? How can I determine why a Linux server is dropping packets?

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Linux set up bluetooth speaker to stream audio from your Android / iOS mobile phone

So how do you stream audio from your Apple iOS or Google Android phone to your laptop speaker? Let us see how to set up a Bluetooth speaker to stream audio from your Android / iOS mobile phone to your Linux based laptop or desktop that got better audio speakers.

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How to install dnscrypt proxy with adblocker on Linux

How do I install the dnscrypt proxy application with an adblocker/malware blocker on Linux operating system with WireGuard or OpenVPN?

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How To Install Speedtest-cli On a FreeBSD To Check Internet Speed

I am using the FreeBSD system. How do I install Speedtest-cli on a FreeBSD Unix system for checking the Internet speed?

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Alpine Linux set up WireGuard VPN server

How do I install and set up WireGuard VPN server on an Alpine Linux cloud server? How can I configure Alpine Linux as the WireGuard VPN server? How can I configure snat to route all VPN traffic on my Alpine Linux?

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How to disable firewall and NAT rules on the LXD bridge

I followed your Ubuntu LXD tutorial, and I noticed LXD automatically created firewall and NAT rules. Is there any way to disable this feature? I want to manage a firewall using custom rule sets. How can I disable firewall and NAT rules on the LXD bridge under Linux?

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How To Set Up a Firewall with Awall on Alpine Linux

Alpine Wall (Awall) is an easy to use interace to iptables for Alpine Linux users. While iptables and ip6tables is an excellent command, it can be challenging for new Alpine Linux users. The awall tool has easy to follow high-level concepts such as zones, limits, policies, and a single source for both IPv4 and IPv6. This tutorial will show you how to set up a firewall with Awall on Alpine Linux.

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UNIX / Linux PGP TarBall File Signature Keys Verification

{Updated} For all FOSS based project, you should download the PGP signatures and MD5/SHA hashes and verify them before using them for security reasons. Learn how to verify the PGP key against downloaded software under Linux / UNIX / *BSD and macOS using the GNU Privacy Guard or any OpenPGP-compliant program.

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Quick tip: Display banner/message before OpenSSH authentication

Want to display a message or banner before OpenSSH (SSHD server) authentication? Try this simple tip to show the banner or ASCII logo on your Linux or Unix system.

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Linux / UNIX kill unresponsive hung SSH session

{Updated} Sometimes my ssh session stops working because of the internet connection problem. I tried pressing CTRL-Z and CTRL-C to terminate my ssh session but failed to work. How do I properly kill a hung SSH session without killing my local terminal or using the kill command? How can I kill unresponsive hung SSH session on macOS?

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Alpine Linux Change Hostname (computer name)

I am a new Alpine Linux user. By default, my server name is set to 'localhost' during installation. Now, I would like to change the computer name. How do I change the Alpine Linux computer name? Can you tell me more about Alpine Linux change hostname command?

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How to enable firewalld logging for denied packets on Linux

{Updated} How do I enable FirewallD logging for denied packets on Linux operating systems so that I can view all dropped packets information? How can I view a log of the traffic blocked by FirewallD under a CentOS/RHEL (Red Hat Enterprise Linux)/Suse/OpenSUSE Linux?

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How to find and delete directory recursively on Linux or Unix-like system

{Updated} I type 'find . -type d -iname foo -delete command to find all foo directories and delete them. However, I am getting an error message that read as, find: cannot delete './hourly.4/data/foo': Directory not empty on my Linux server. How do I delete directories based on find command output on Linux or Unix-like system?

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tmpmail – A temporary email right from Linux / Unix terminal

Are you looking to send a temporary email right from your Linux or Unix terminal? Look no further. Try tmpmail command-line utility that allows you to generate a temporary email address for receiving emails. Underneath the script uses 1secmail's API to receive the emails.

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How to Install Java on Ubuntu 20.04 LTS Linux

Can you explain how to install Java on Ubuntu 20.04 LTS Linux system?

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How To Protect SSH With Fail2Ban on CentOS 8

{Updated} My ssh log file shows too many password failures. Random IP address trying to brute force my sshd server running on CentOS 8 server. How do I protect ssh with fail2ban on CentOS 8 Linux server? How do I install Fail2Ban on CentOS 8?

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How to create a Linux swap file

I am a new Linux system developer and user. How do I create a Linux swap file from the command line option for my cloud server? How can I add swap space on my Ubuntu 20.04 LTS or CentOS Linux 7/8 server?

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How do I know if my Linux is 32 bit or 64 bit?

{Updated} I need to find out if my Linux server is running on 32-bit or 64-bit system. How do I know if my Linux is 32 bit or 64 bit?

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How to check if CentOS / RHEL needs a full reboot

I am using a CentOS/RHEL 6/7/8 server. How do I check from the command line if a reboot is required for my CentOS host? How do I check if a host powered by CentOS Enterprise Linux needs to reboot after running the yum update command?

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How to install kotlin programming language on Ubuntu/Debian Linux

{Updated} How do I install the latest version of kotlin programming language on Ubuntu or Debian Linux system?

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How to use ssh-agent for authentication on Linux / Unix

How do I use the ssh-agent command for non-interactive authentication on Linux and Unix-like systems such as macOS or FreeBSD desktop? My private key is protected with a passphrase or password. So I need have to enter the passphrase to use the ssh private key for authentication multiple times. How can I tell ssh ask the passphrase one time only?

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Top 15 XKCD comics for Linux and Unix fans

Linux is a free and open-source kernel developed by Linus Torvalds, a Unix-like operating system clone. XKCD comic has a long tradition for including humorous geeky cartoons. In this post, I pick my favorite XKCD comics for Linux and Unix fans.

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FreeBSD configure AWS SES with Postfix MTA

How do I integrate and configure Amazon/AWS SES with Postfix running on my FreeBSD Unix server?

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Linux Dell Server / Desktop / Laptop Find Out Service Tag Command

{Updated} I need to find out the service tag of my Dell server or computer. How do I find out my unique five- to seven-digit alphanumeric (letter and number) service tag code without looking at the back of the system or opening the door of bezel? Is there is Linux command to get the Dell service tag from the Terminal?

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Linux / UNIX List Open Files for Process

{Updated} How do I list all open files for a Linux or UNIX process using command line options? How can I show open files per process under Linux?

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How to view status of a service on Linux using systemctl

How do I use the systemctl command to view status of a systemd service on Linux operating systems?

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How to install and setup PostgreSQL on RHEL 8

{Updated} How do I install PostgreSQL relational database management on RHEL 8 using the command line? How do I install and setup PostgreSQL on RHEL 8 (Red Hat Enterprise Linux) server using application streams?

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Linux and Unix Test Sequential Disk I/O Performance With dd Command

{Updated} You can use the following commands on a Linux or Unix-like systems for simple sequential I/O performance test

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BASH Prepend A Text / Lines To a File under Linux, macOS and Unix

{Updated} I am a new Unix system user with a bash as a default shell. I can append text to a file using >> operator but how do I prepend a text to a file? I want the opposite operation of >> operator. How can I prepend some data to a text file? How do we add text to the beginning of a file in Bash under Linux?

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How to save iptables firewall rules permanently on Linux

I am using Debian / Ubuntu Linux server. How do I save iptables rules permanently on Linux using the CLI added using the iptables command? How can I store iptables IPv4 and IPv6 rules permanently on the Debian Linux cloud server?

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How to find ip address of Linux KVM guest virtual machine

{Updated} How do I find out an IP address of Linux KVM guest from Linux host itself? I wanted to ssh into KVM guest VM. How can I find the IP address of a KVM Virtual Machine Guest on a CentOS Linux 7.x/8.x server?

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How to install less on CentOS / RHEL / Fedora

One of my PHP and bash scripts depends upon less command to display the help system to other users. But, whenever they run less on a particular version of CentOS or RHEL cloud server, they get an error that reads as: "bash: less: command not found." How do I install less utility on CentOS or RHEL (Red Hat Enterprise Linux)/Fedora Linux server? How can I configure Linux containers such as Docker or Podman to install less automatically?

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How to write the output into the file in Linux

How do I write the output into the file in Linux bash shell? Can you explain I/O redirection for both bash and POSIX shell to write data to the file under Unix or Linux?

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SSH Into Google Cloud Compute Engine Instance Using Secure Shell Client

{Updated} I need to set and test my web-app using Google cloud compute engine. How do I connect to an Instance Using ssh from my Ubuntu Linux or Apple OS X/macOS desktop?

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How to backup and restore LUKS header on Linux

Previously I explained how to encrypt Linux partitions or disk with the LUKS (Linux Unified Key Setup)/dm-crypt. In this quick blog post, I will explain how to backup and restore LUKS header for emergency purposes. Backup is useful for recovering from misconfigurations, corrupted headers or forgotten passphrase or unknown password.

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How to set/change FQDN on Ubuntu 20.04 Linux

How do I set/change my server's Fully Qualified Domain Name (FQDN) on Ubuntu 20.04 LTS "Focal Fossa" Linux?

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Bash Shell Ignore Aliases and Functions When Running A Command

{Updated} How do I ignore bash shell aliases or functions when running a command without removing alias or function from memory or current shell session on a Linux or Unix-like systems?

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How to add days to date and get new date on Linux

I brought eggs from the market, and it says best before 20 days from the date of packing. Say my egg box was packed on 29/July/2020. How do I add days to date using Linux CLI? I want to find out date 29/July/2020 + 20days using the CLI, and how do I do it?

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Thinkpad laptop update firmware/bios on Linux

{Updated} You need to keep firmware updated, and it is an essential task for system stability and to fix bugs. The latest models of Lenovo ThinkPads can update the firmware using the Linux Vendor Firmware Service (LVFS). When updates are published on LVFS, GNOME/KDE can notify you about upgrades. Installing the firmware on Linux wasn't easy, as most vendors only supported the Windows family of operating systems. However, older Thinkpad models can be still updated without using Windows.

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Set up automatic unattended updates for Ubuntu 20.04

How do I configure automatic unattended updates for Ubuntu Linux 20.04 LTS "Focal Fossa" server?

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Find command Exclude or Ignore Files (e.g. Ignore All Hidden .dot Files )

{Updated} How do I ignore all hidden .dot files while searching for files using the find command? How do I ignore or exclude certain files while running Linux or UNIX find command?

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How To Force apt-get with IPv4 or IPv6 Transport (address) on a Ubuntu or Debian or Mint Linux

{Updated} It is possible that I can forces my apt-get command/apt command only use IPv6 or Ipv4 transport on a Debian or Ubuntu Linux server?

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How to install htop on Arch Linux

I am a new user of Arch Linux operating system. How do I install htop on Arch Linux using the pacman command?

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