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On Linux systems, the root filesystem (/) can be on various device types — a raw disk partition, an LVM logical volume, or other storage configurations. Finding the underlying physical disk requires checking the device hierarchy, which differs depending on the storage setup. Quick method with df and lsblk The simplest approach uses lsblk with…
Sometimes you need to find the ASCII character that comes after a given character. This is useful for generating sequences, creating substitution ciphers, or manipulating character ranges in shell scripts. Using printf with ASCII Values The most portable and straightforward approach uses printf to convert between characters and their ASCII numeric values: #!/bin/bash get_next_char() {…
If you’re running dnsmasq primarily for DNS resolution and don’t need its DHCP server capabilities, you’ll want to disable DHCP while keeping DNS functional. This is a common configuration for DNS-only setups or when another service handles DHCP. Default dnsmasq behavior By default, dnsmasq ships with DHCP disabled. However, many distributions include preconfigured DHCP settings…
Extracting or removing trailing numbers from strings is a common task in shell scripting. Whether you’re parsing log files, processing configuration values, or cleaning up filenames, you’ll need reliable methods to handle these operations. Using Parameter Expansion The cleanest approach uses bash parameter expansion, which doesn’t require external commands and works in all POSIX-compliant shells….
Bash doesn’t have a built-in split function, but you can achieve string splitting through several methods. The most common approach uses IFS (Internal Field Separator), though other techniques exist depending on your needs. IFS with read The simplest method for splitting a string by a delimiter: string=”apple,banana,cherry” IFS=’,’ read -ra ADDR <<< “$string” for i…
The gethostname() function is the standard POSIX way to retrieve the system’s hostname. It’s straightforward to use and works across Unix-like systems. Basic Implementation #include <unistd.h> #include <stdio.h> int main() { char hostname[256]; if (gethostname(hostname, sizeof(hostname)) == 0) { printf(“Hostname: %s\n”, hostname); } else { perror(“gethostname”); return 1; } return 0; } The function takes…
Bash provides straightforward methods to convert Unix epoch timestamps into human-readable formats. This is essential for log parsing, system monitoring, and scripting across CI/CD pipelines and production environments. Using the date Command The standard approach is the date command with the -d flag (GNU coreutils) or -r flag (BSD/macOS): Linux (GNU date) date -d @1234567890…
Retrieving the hostname of the machine running your script is essential for logging, node identification in distributed systems, monitoring, and conditional logic based on where code executes. Bash offers multiple approaches with different tradeoffs. Using the $HOSTNAME Variable The quickest method is the $HOSTNAME environment variable, which Bash sets at shell initialization: echo $HOSTNAME host01…
The date command is your primary tool for retrieving Unix epoch timestamps. It’s available on virtually all Unix-like systems and integrates seamlessly into scripts and command pipelines. Basic Epoch Timestamp date +%s This returns the number of seconds since January 1, 1970 UTC. Output looks like 1735689600. Higher Precision with Nanoseconds For microsecond or nanosecond…
Environment variables store configuration settings for your shell and applications. They’re essential for configuring containers, serverless functions, application runtime behavior, and system services. Retrieving an environment variable Use the dollar sign prefix to access a variable: echo $VARIABLE_NAME This prints the variable’s value to stdout. If the variable doesn’t exist, it prints an empty line….
Bash provides several methods to process files line by line, each with different performance characteristics and use cases. Using a While Loop with IFS The most common approach uses a while loop with the read builtin: while IFS= read -r line; do echo “Processing: $line” done < filename.txt Breaking this down: IFS= prevents leading/trailing whitespace…
The most straightforward way to convert SVG files to PNG is using ImageMagick or Inkscape. Both are widely available in standard repositories and handle the conversion reliably. Using ImageMagick (convert/magick) ImageMagick provides the magick command (the modern equivalent to the older convert utility): magick input.svg output.png For basic conversions, that’s all you need. To control…
There are several ways to retrieve the hostname on a Linux system from Python. The choice depends on your use case and whether you need the simple hostname or the fully qualified domain name (FQDN). Using socket.gethostname() The simplest approach uses the socket module from the standard library: import socket hostname = socket.gethostname() print(hostname) This…
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…
Linux doesn’t provide a glibc wrapper for ioprio_set(), so you need to call it directly via syscall(). Here’s the basic approach: #include <unistd.h> #include <sys/syscall.h> syscall(SYS_ioprio_set, IOPRIO_WHO_PROCESS, pid, ioprio_value); Required definitions You’ll need to define the I/O priority classes, target types, and helper macros. Add these to your source file or header: /* I/O priority…
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…
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…
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…