Most modern systems have thermal sensors built into the CPU and motherboard. Reading these sensors is essential for monitoring system health, diagnosing performance issues, and preventing thermal throttling or hardware damage. Install lm-sensors The standard tool for reading hardware sensors on Linux is lm-sensors. Install it on your system: Debian/Ubuntu: sudo apt install lm-sensors RHEL/CentOS/Fedora:…
When running scripts as root, you often need to execute commands with the environment of a different user. The most reliable way to retrieve another user’s PATH is by spawning a login shell under that user’s context. Basic Approach user1path=$(su – user1 -c ‘echo $PATH’) This spawns a login shell (-) as user1 and outputs…
When writing system administration scripts, you often need to check if a user account exists before taking action. There are several reliable methods to accomplish this. Using id command The id command retrieves user information and returns a non-zero exit code if the user doesn’t exist. This makes it ideal for conditional testing: user=”hello” if…
To identify the developers who’ve contributed the most commits to a repository, use git log with some text processing: git log –format=’%aN’ | sort | uniq -c | sort -rn This returns a sorted list with commit counts and author names: 247 Paul Phillips 45 Dale Wijnand 12 Yamashita Yuu 10 Gilles Cornu 8 Josh…
Bash provides several straightforward ways to test whether a string contains a substring. The best approach depends on your use case and performance requirements. Using [[ ]] with glob patterns The fastest and most Bash-native method is the [[ conditional construct with glob patterns: if [[ “$string” == *”substring”* ]]; then echo “Found it!” fi…
When stop-dfs.sh fails to cleanly terminate DataNode processes, you’re left with orphaned Java processes consuming resources and potentially causing cluster issues. This happens most often after ungraceful cluster shutdowns or when the standard stop script encounters communication problems with specific nodes. Understanding the Problem The typical symptom is stop-dfs.sh reporting that certain nodes have no…
Merging SAM files is a common task in bioinformatics workflows, and while samtools merge works directly with BAM files, you need a different approach for SAM files. The most efficient method leverages the SAM format structure: headers start with @, and alignment records don’t. Why not convert to BAM first? Converting SAM to BAM, merging…
When submitting images to publishers or print shops, you’ll often need CMYK color space instead of RGB. The conversion is straightforward on Linux using ImageMagick’s convert command. Basic conversion The simplest approach uses the -colorspace option: convert from.tif -colorspace CMYK to.tif This works, but CMYK TIFF files can be quite large. Add compression to keep…
While BIOS settings are the preferred way to disable USB 3.0, you can also force USB 2.0 mode on a running Linux system by manipulating the xHCI controller’s port routing register directly using setpci. How it works Intel xHCI controllers use the XUSB2PR (xHC USB 2.0 Port Routing Register) at offset 0xd0. Setting this register…
When you need the commit hash of the latest commit, there are several ways to get it. The most direct approach is using git log with format options rather than parsing output with grep. Using git log with –format The cleanest method is to use git log with the –format option: git log -1 –format=”%H”…
These kernel messages from the libata driver indicate SATA link-layer errors between your drive and controller. They look alarming, but they’re usually fixable — and the fix is typically hardware-related, not a software or drive firmware issue. What These Error Messages Mean When you see messages like this in dmesg: ata4.00: exception Emask 0x10 SAct…
YouCompleteMe’s installation script fails on Fedora with a CMake error about missing PYTHON_LIBRARIES and PYTHON_INCLUDE_DIRS, even when Python is already installed. The error looks like this: CMake Error at /usr/share/cmake/Modules/FindPythonLibs.cmake:201 Could NOT find PythonLibs (missing: PYTHON_LIBRARIES PYTHON_INCLUDE_DIRS) The issue is that you have the Python runtime libraries installed but not the development headers needed for…
When your application fails to bind to a port, you need to identify what’s already using it. This is one of the most common debugging tasks in Linux system administration. Using ss (Modern Approach) The ss command has largely replaced netstat in modern Linux distributions. It’s faster, more efficient, and provides clearer output: ss -ltnp…
VirtualBox on Fedora reports “The vboxdrv kernel module is not loaded” when you try to launch it, even though the virtualbox and kernel module packages are installed. This typically happens on systems with UEFI Secure Boot enabled, which requires kernel modules to be cryptographically signed. Check if the module is loaded First, verify whether the…
When writing C programs on Linux that handle file paths, you need to allocate buffers safely. The kernel defines maximum path and filename lengths through standard macros in <linux/limits.h>. Getting the limits On Linux systems, <linux/limits.h> provides two key macros: NAME_MAX — maximum length of a single filename component (255 characters) PATH_MAX — maximum length…
Finding files that match a pattern is straightforward with ls *string* or find . -name ‘*string*’. But excluding files with a certain string in their filename requires a different approach. Using find with negation The most reliable method is find with the ! (or -not) operator: find . -type f ! -name ‘*string*’ This finds…
When managing packages on Ubuntu or Debian systems, knowing what versions are available—and which one will be installed—is essential for dependency management and system stability. The aptitude command provides several ways to inspect package versions. Check all available versions of a package The most straightforward approach is to use the versions subcommand: aptitude versions package-name…
When you run cat /etc/resolv.conf on a modern Linux system, you’ll often see nameserver 127.0.0.1 or 127.0.1.1 pointing to localhost. This doesn’t mean you’re actually using your ISP’s DNS directly — it usually means your system is running a local DNS stub resolver or caching service like systemd-resolved or dnsmasq. To find out which actual…
Vim determines file types by extension to apply syntax highlighting and indentation. If you have custom file extensions that should be treated as C files, you need to configure Vim to recognize them. Using autocommand in .vimrc Add an autocommand to your ~/.vimrc: ” Treat .h and .c files in a custom directory as C…
Detecting whether an image is predominantly blank, black, or contains minimal content is useful for automated workflows like batch processing, quality control, or identifying failed captures. Here’s how to do it reliably on Linux. Using ImageMagick ImageMagick’s convert command (or magick in newer versions) can extract image statistics to determine if an image is nearly…