Programming languages and software development
The most direct way to check for key existence is the in operator: if ‘key’ in my_dict: print(“Key exists”) This is O(1) average case and the idiomatic Python approach. It’s fast and readable. Alternatives Based on Your Use Case Using dict.get() when you need the value: value = my_dict.get(‘key’) if value is not None: print(f”Key…
Spaces in file and directory paths are a common source of rsync failures. When paths contain spaces, the shell interprets them as argument separators unless you properly escape or quote them. Here’s how to handle this correctly. The core issue When rsync receives an unquoted path with spaces, the shell splits it at each space….
VM exits occur when a guest VM transitions to hypervisor mode to handle privileged operations, I/O requests, or other events. Tracking exit counts and types helps identify performance bottlenecks, inefficient guest behavior, and hypervisor overhead. Quick Exit Statistics The debugfs interface provides a simple view of exit counts: cat /sys/kernel/debug/kvm/exits This shows aggregate exit counts…
aria2 is a lightweight, multi-protocol download manager that supports HTTP(S), FTP, BitTorrent, and Metalink protocols. It’s particularly useful for resumable downloads, parallel connections, and command-line automation. Prerequisites You’ll need root or sudo access. This guide covers CentOS 7, CentOS Stream, and Rocky Linux 8+. For older systems still on CentOS 7, package availability may be…
curlftpfs is a FUSE-based filesystem that lets you mount FTP/SFTP servers as local directories. This is useful for treating remote FTP locations like local storage without downloading files individually. Prerequisites FUSE kernel module loaded (usually default on modern systems) Root or sudo access Network connectivity to your FTP server Installation on RHEL/CentOS/Rocky Linux The curlftpfs…
When you create VMs in KVM, they’re typically assigned IP addresses via DHCP. Finding those addresses so you can SSH in requires a few steps. Here are the practical approaches. Using virsh domiflist and ARP The traditional method combines virsh domiflist to get the VM’s MAC address, then looks it up in the ARP table:…
SSHFS isn’t available in the default repositories on most RHEL-based distributions. If you try to install it directly, you’ll get an error: # yum install sshfs No package sshfs available. Error: Nothing to do The package lives in EPEL (Extra Packages for Enterprise Linux), so you need to enable that repository first. Enable EPEL For…
VNC (Virtual Network Computing) provides a graphical remote desktop connection to Linux servers. It’s straightforward to set up and useful when you need GUI access to a headless or distant system. Installation On the server side, install a VNC server package. TigerVNC is the most reliable choice across distributions: Debian/Ubuntu: sudo apt install tigervnc-server tigervnc-common…
Adobe Flash Player reached End of Life on December 31, 2020, and Adobe blocked all Flash content from executing in 2021. Installing Flash Player on CentOS 7 in 2026 is neither practical nor recommended—the plugin won’t execute Flash content anyway, and doing so introduces security vulnerabilities to your system. If you’re still running CentOS 7,…
The RTL8192cu is a legacy USB WiFi adapter that’s still in use, but it has known stability issues on modern kernels. If your adapter keeps dropping connections or fails to resume after sleep, you’re likely hitting the same power management bug that affects many devices. Disable power management The most reliable workaround is to disable…
Configuring multiple static IP addresses on a Xen VM is useful for hosting multiple services, SSL certificates, or failover scenarios. The approach depends on your underlying Linux distribution and whether you’re using traditional network configuration or modern network managers. Using ip Command for Immediate Changes The quickest way to add a secondary IP is with…
The NAS Parallel Benchmarks (NPB) remain a standard tool for evaluating HPC system performance, though landscape has shifted toward additional metrics like HPCG and memory bandwidth tests. This guide covers installation and basic usage. Prerequisites Before installing NPB, you’ll need: Fortran compiler — gfortran is the standard choice on most systems MPI implementation — OpenMPI…
NFS squashes root access to an anonymous user (typically nobody) by default as a security measure. When a client connects as root, the server remaps that user to an unprivileged account, preventing root from having unrestricted access to exported shares. This can cause permission issues if your application genuinely requires root-level file operations. Using no_root_squash…
PARSEC is a widely-used CPU-bound benchmark suite containing real applications and complex third-party library dependencies. The installation can be challenging due to these external requirements, but following this guide will get you up and running. Prerequisites Before starting, install the required build tools and libraries: sudo apt-get update sudo apt-get install build-essential pkg-config gettext autoconf…
Different projects and languages have different indentation conventions. Rather than manually adjusting settings each time you switch contexts, you can define custom commands in Vim to toggle between common tab widths quickly. Using Custom Functions and Mappings Add these functions to your ~/.vimrc: function SetTab2() set shiftwidth=2 set tabstop=2 set softtabstop=2 echo “Set tab to…
The “invalid syntax, continuing…” warning from sysctl typically means your /etc/sysctl.conf file has a malformed line that the parser can’t understand. Here’s how to diagnose and fix it. Identifying the Problem When you run sysctl -p to load configuration from /etc/sysctl.conf, any syntax error will be printed with a line number: sysctl -p warning: /etc/sysctl.conf(44):…
If you already have PHP and nginx running on Rocky Linux 9 and need to add or update glibc, glibc-common, and GD libraries independently, you can do so safely without disrupting your existing installation. Understanding the dependencies glibc: The GNU C Library — the core runtime library for nearly all C programs on Linux glibc-common:…
Error handling is fundamental to Go development. Often you’ll need to convert an error to a string for logging, displaying to users, or including in API responses. Go provides several straightforward approaches. Using the Error() Method Every error in Go implements the error interface, which has a single method: Error() string. The simplest conversion is…
In Go, a string is a read-only slice of bytes, while a rune is an alias for int32 representing a Unicode code point. Understanding this distinction is essential when you need to work with individual characters, especially in multilingual text. Basic Conversion The simplest approach is direct type conversion: s := “Hello, 世界” runes :=…
Sending output to stderr keeps error messages separate from normal program output, making it easier to redirect and filter logs in shell scripts and pipelines. Basic Approach with fmt The simplest method uses fmt.Fprintln() with os.Stderr: package main import ( “fmt” “os” ) func main() { fmt.Fprintln(os.Stderr, “This is an error message”) } This writes…