Disabling a user account is a common administrative task. Whether you’re offboarding an employee, removing an unused service account, or securing a compromised account, there are several approaches depending on your requirements. Lock the account with usermod The simplest method is to lock the password hash: sudo usermod -L username This prepends an exclamation mark…
Process priority management is essential for ensuring critical tasks get CPU resources when needed. Linux provides several mechanisms to control how the kernel scheduler allocates CPU time to processes. Understanding Priority Levels Linux uses two priority concepts: Nice value: ranges from -20 (highest priority) to 19 (lowest priority). Default is 0. Real-time priority: ranges from…
When upgrading libvirt from an older version (like 1.2.2) to 2.5.0 or later, you may encounter a socket connection error when trying to create VMs: ERROR Failed to connect socket to ‘/var/run/libvirt/virtlogd-sock’: No such file or directory Domain installation does not appear to have been successful. This happens because libvirt 2.5.0 introduced the virtlogd daemon…
After a libvirt upgrade, VMs fail to start with the error: error: Failed to start domain kvm1 error: Network not found: no network with matching name ‘default’ This happens when the default NAT network (virbr0) isn’t automatically created during the upgrade. Quick fix: Restore the default network The fastest solution is to recreate the default…
EncFS provides an encrypted filesystem in user space — files are encrypted on the fly and stored in an existing directory. It’s lighter than LUKS and doesn’t require root access or dedicated partitions. Here’s how to set it up on CentOS 6. Install EncFS EncFS is available from the EPEL repository: # Enable EPEL sudo…
Sometimes you need an older version of Hadoop — for compatibility with existing jobs, to reproduce bugs, or to match a specific cluster environment. The Apache Hadoop project maintains an archive of all past releases. From the Apache Archive All Hadoop releases are available from the Apache Software Foundation’s distribution archive: https://archive.apache.org/dist/hadoop/common/ Browse the directory…
The default TeX Live packages available through standard repositories are often outdated and incomplete. The official TeX Live installer provides access to current versions and the full package collection, though it requires around 4-5GB of disk space. Prerequisites Before starting, ensure you have the required dependencies installed: sudo yum groupinstall -y “Development Tools” sudo yum…
There are several tools available for extracting images from PDFs on Linux, each with different strengths depending on your use case and the PDF structure. pdfimages (Poppler Utils) The most straightforward approach is using pdfimages from the poppler-utils package: pdfimages document.pdf image This extracts all images and saves them as image-000.ppm, image-001.ppm, etc. By default,…
Getting kernel function call stacks is essential for debugging driver issues, understanding kernel behavior, and performance profiling. The approach depends on what you’re trying to trace: live kernel execution, crash analysis, or post-mortem inspection. Using ftrace The kernel’s built-in ftrace framework is the first tool to reach for. It’s zero-overhead when disabled and has minimal…
When trying to mount an encrypted EncFS directory as a normal user, you may encounter this error: $ encfs -s ~/t/.enc ~/t/enc EncFS Password: fuse: failed to exec fusermount: Permission denied fuse failed. Common problems: – fuse kernel module not installed (modprobe fuse) – invalid options — see usage message Even though the same command…
Dia is a GTK+ based diagram creation program for Linux. It supports flowcharts, network diagrams, circuit diagrams, UML diagrams, and many other types. Here’s how to install and get started with Dia on CentOS 7. Install Dia from EPEL Dia is available in the EPEL (Extra Packages for Enterprise Linux) repository: # Enable EPEL if…
The most common need is collapsing multi-line records into single lines. Here are the practical approaches: Using tr to remove newlines The simplest method removes all newlines: tr -d ‘\n’ < input.txt > output.txt This works well for data without embedded line breaks you want to preserve. For CSV or structured data where you need…
When running Ubuntu on older servers like Dell PowerEdge systems with legacy graphics cards (Matrox G200eR2, etc.), you may encounter extremely slow desktop performance. The issue typically stems from the X server falling back to unoptimized drivers or incorrect video mode detection. Identifying the problem First, check your current graphics configuration: lspci | grep -i…
The bottom panel in GNOME Classic displays the window list via the “Window List” extension. If you don’t use it, there are several ways to remove it depending on your approach. Method 1: Context menu removal (Recommended) The simplest approach if your GNOME version supports it: Hover over a blank area of the bottom panel…
The most common approach is using Apache’s mod_rewrite module. Add this to your .htaccess file in your document root: <IfModule mod_rewrite.c> RewriteEngine On RewriteCond %{HTTP_HOST} !^www\. [NC] RewriteCond %{HTTP_HOST} !^$ RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [L,R=301] </IfModule> This uses a 301 permanent redirect, which tells browsers and search engines that the www version is canonical. The conditions…
XSANE is a graphical scanner interface for Linux that provides straightforward scanning capabilities. When you scan documents or images, the JPEG output files can be surprisingly large depending on your settings. Here are practical methods to reduce the file size. Adjust JPEG Quality in XSANE The most direct approach is to lower the JPEG quality…
The screen terminal multiplexer can capture window output in several ways. Here are the most practical approaches depending on your use case. Enable logging before starting screen Start a new screen session with the -L flag to log all output to a file: screen -L -S mysession This creates a log file named screenlog.0 in…
HP printers and scanners on Rocky Linux, CentOS, or RHEL require the HPLIP (HP Linux Imaging and Printing) package. This guide covers the complete setup process. Install HPLIP packages Start by installing the core HPLIP packages: sudo dnf install hplip hplip-gui hpijs On older CentOS 7 systems, use yum instead of dnf. HPLIP may prompt…
The tee command by default reads from stdin and writes to both stdout and files. To capture only stderr, you need to explicitly redirect it. Basic stderr redirection to tee The straightforward approach is to redirect stderr to stdout, then pipe to tee: command 2>&1 | tee output.log This captures both stdout and stderr. If…
Temporary files are essential for any non-trivial Bash script. Whether you’re processing data, staging changes, or handling inter-process communication, you need reliable ways to create uniquely-named files that won’t collide with other processes. Using mktemp The standard and most reliable approach is mktemp, which generates a cryptographically random temporary filename: tmpfile=$(mktemp) echo “Temporary file created…