The article explains how the Linux kernel discovers and calls module initialization functions like inet_init by using the fs_initcall macro, which creates static initcall variables placed in specially‑named sections that the linker groups and the kernel iterates at boot time.
This article explains how Linux 3.10 organizes memory using NUMA nodes, zones, the buddy system, and the SLAB allocator, providing commands, code examples, and visual diagrams to illustrate each layer of the kernel's efficient memory management.
This article explains the Linux kernel memory management hierarchy—including NUMA nodes, memory zones, the buddy system for free pages, and the SLAB allocator—providing command‑line examples, code snippets, and visual diagrams to illustrate how the kernel efficiently allocates and reclaims memory.
This article explains common awk built‑in variables such as OFS, NR, and NF, demonstrates practical awk one‑liners for extracting and formatting /etc/passwd data, and shows how to use netstat (and ss) together with awk to monitor network connection states on a Linux system.
This guide walks Linux operations engineers through common signs of a compromised host—such as missing logs, altered password files, unexpected login events, and deleted critical files—and provides concrete command‑line techniques for detection, investigation, and recovery using tools like ll, du, lastlog, who, lsof, and tcpdump.
This guide outlines comprehensive Linux security hardening steps—including account protection, service minimization, password policies, sudo usage, file system safeguards, rootkit detection tools, and post‑attack response—to help operations teams secure their servers against common threats.
This article introduces the five Linux I/O models—blocking, non‑blocking, I/O multiplexing, signal‑driven, and asynchronous—explaining core concepts such as blocking vs non‑blocking calls, synchronous vs asynchronous processing, and detailing each model’s execution phases, advantages, and typical use‑cases.
Teen developer Daniel Rodriguez repurposes a non‑functional iPhone 7 by jailbreaking it, building a custom Ubuntu 20.04 root filesystem, compiling a tailored kernel, and using projectsandcastle and PongoOS to boot Linux, effectively turning the device into a networked ARM64 server.
This guide explains how to configure Ansible inventory, write a YAML playbook that updates the root password on two servers, execute the playbook, and verify the password change through SSH login, illustrating a flexible automation workflow for multi‑host deployments.
This guide introduces the most useful Linux text‑viewing commands—including cat, tac, more, less, head, tail, sort, sed, uniq, and vi—explaining their basic syntax, common options, and practical examples for efficient file inspection and manipulation.
This guide explains how to set up SSH certificate‑based authentication by creating a Certificate Authority, generating user and host keys, signing certificates, configuring both server and client to trust them, and managing revocation, offering a more secure alternative to password or key‑pair logins.
This guide walks through preparing the Linux environment on Kubernetes master and node machines, creating a bare Git repository, configuring SSH access, cloning the repository, and demonstrating core Git commands such as add, commit, status, diff, and push to a remote server.
This guide shows how to transform an outdated 2011 13‑inch MacBook Pro into a usable Linux machine by creating a Fedora 33 live USB, installing the OS, and configuring the Broadcom Wi‑Fi driver, all within about an hour of work.
This article explains how to use the Linux export command to set and view environment variables, demonstrates common options such as listing all exports, exporting specific variables, exporting functions, and shows how to persist settings in shell configuration files, providing practical examples for beginners.
This guide walks you through configuring SSH key‑based authentication, generating a public‑private key pair, copying the public key to a remote server, and using ssh‑agent to cache your passphrase for seamless logins.
This guide walks through the complete GCC compilation pipeline—preprocessing, compilation, assembly, and linking—using a simple C "Hello World" program, detailing each step, relevant commands, and how to inspect the resulting ELF binary.
This article explains the layered design of Linux file I/O, describes how data moves from application buffers through libc, page cache, and kernel I/O queues to disk, discusses synchronization primitives, consistency issues, and performance factors such as scheduling algorithms and hardware characteristics.
This guide explains why password‑based SSH logins are insecure, introduces asymmetric key concepts, walks through generating key pairs with ssh‑keygen, uploading public keys manually or via ssh‑copy‑id, using ssh‑agent and ssh‑add to manage passphrases, and disabling password authentication for hardened server access.
This article provides a comprehensive overview of Linux's core components—including the kernel, memory and process management, virtual file system, device drivers, network stack, shell variants, file types, directory hierarchy, partitioning, mounting, and essential command‑line tools—while illustrating each concept with diagrams and code examples.
This guide walks you through querying a Linux server's basic configuration—including OS version, kernel, CPU specs, memory usage, disk usage, and block device details—using common command‑line tools with clear examples and explanations.
This article explains the Linux ps command, its purpose, common options, process states, and provides practical examples such as pstree, ps ‑Lf, pstack, kill signals, and various ps usages for listing all processes, filtering by user, and combining with grep.
Learn how to securely copy files between local and remote machines using the scp command, covering basic syntax, authentication options, copying to and from remote hosts, recursive directory transfers, and transferring between two remote servers, all illustrated with practical examples.
This guide provides system administrators with a step‑by‑step checklist to audit and harden Linux operating systems, covering account management, password policies, service restrictions, filesystem permissions, logging configuration, and practical command examples for comprehensive security compliance.
This article provides a step‑by‑step guide to preparing the operating system, installing and configuring MySQL, tuning system parameters, and using a Bash one‑click deployment script to automate the setup and initialization of a MySQL 5.7.32 instance on Linux.
This article introduces ten fundamental Linux commands—pgrep, pstree, bc, split, nl, mkfifo, ldd, col, xmlwf, and lsof—explaining their purposes, typical usage examples, and how they can help developers and system administrators work more efficiently on Unix-like systems.
This article provides a comprehensive, step‑by‑step tutorial for setting up a three‑node Ceph storage cluster on CentOS 7.9, covering host configuration, firewall and SELinux settings, package installation, monitor, manager, OSD, MDS, and RGW deployment, along with required keyrings, configuration files, and troubleshooting tips.
Learn how to use the Linux tar command to archive files and directories, explore options for creating, listing, and extracting archives, and compare gzip, bzip2, and xz compression methods with performance metrics and practical examples.
This guide explains why careful file deletion matters, introduces Linux tools like lsof and extundelete for recovering accidentally removed files, and provides step‑by‑step commands, installation instructions, and precautions to successfully restore data from ext3/ext4 partitions.
This guide walks through installing Gogs, creating a start‑up script, configuring a systemd service, launching the server, checking its status, creating repositories via the web UI or command line, and pushing code with saved credentials, all on a Linux host.
A comprehensive reference of over two hundred Linux command‑line utilities, grouped by function such as file management, system monitoring, networking, user administration, and process control, each with concise English descriptions to help beginners and seasoned administrators quickly find the right tool for any task.
Upgrading a production Linux server safely requires thorough preparation—including full backups, verifying software compatibility, using a temporary server and load balancer, and scheduling the upgrade during low traffic—to avoid data loss, downtime, and performance issues.
This article explains the relationship and differences among 32‑bit and 64‑bit hardware, operating systems, and applications, covering CPU families, Linux and Windows OS variants, compatibility layers, and how to identify architecture using simple commands.
This article explains what inodes are, why they can become exhausted despite available disk space, and provides practical Linux commands and preventive steps to identify and resolve inode exhaustion issues.
This guide walks through installing MariaDB, creating a Gogs database and user, setting up Git, extracting and launching Gogs, and configuring the application—including disabling registration—to complete a simple self‑hosted Git server on Linux.
This article explains how Linux manages TCP sockets at the kernel level, shows how to adjust system limits for massive concurrent connections, walks through key source code such as sock_common, tcp_v4_rcv, and inet_lookup, and provides practical tuning steps to achieve over a million simultaneous client connections.
Ansible is a simple, powerful, agent‑less automation language that uses YAML‑based playbooks to manage configurations, install software, and orchestrate tasks across Linux, Windows, Unix, and network devices; this guide explains its architecture, installation on Ubuntu, configuration files, inventory setup, and common ad‑hoc commands.
A seven‑day series of experiments measures the memory footprint of TCP sockets in various states—including ESTABLISH, data transfer, and TIME_WAIT—showing how the Linux kernel optimizes socket memory usage and what factors influence the actual consumption.
This guide introduces several Linux performance monitoring tools—nmon, perf, top, iostat, sar, dstat, and htop—explaining their functions, key metrics, and installation commands for use on a Huawei Kunpeng server. It also shows how to generate flame graphs with perf and highlights htop's interactive advantages.
This compilation presents Qunar's 2020 technical articles covering domain‑driven design, API standardization, backend services, Linux I/O, Redis distributed locks, GraphQL, JVM internals, and performance optimizations, offering detailed insights and practical guidance for engineers seeking to improve system architecture and operational efficiency.
The article presents a seven‑day series of experiments measuring how much memory a TCP connection occupies in various states—including ESTABLISH, data transfer, and TIME_WAIT—revealing kernel optimizations for socket buffer reclamation and overall memory overhead.
This article provides a detailed Linux tutorial for installing MongoDB, disabling the firewall, extracting the package, setting environment paths, creating data and log directories, editing the configuration file, and launching the database both in foreground and as a background service.
This guide explains how to enrich Linux Bash history with execution timestamps, user and IP information, and how to modify the Bash source to forward history entries to syslog, ensuring tamper‑resistant audit logs for security incident response.
This article traces the origins of Unix and Linux, explains how Linux emerged as an open‑source clone of Unix, compares their licensing, portability, community support, and usage in data centers and devices, and highlights the key distinctions that set the two operating systems apart.
This guide shows how to enrich Linux Bash history with execution timestamps, user and IP information, and forward logs to syslog or a remote server, improving auditability and protecting against tampering during security incident response.
The article explains what inodes are, why they can become fully consumed even when disk space remains, and provides step‑by‑step Linux commands and cron adjustments to identify the offending directories, delete excess files, and prevent future inode exhaustion.
This guide explains why standard rm fails on files with special characters or leading dashes and provides six reliable techniques—including using a path prefix, the "--" separator, quoting, escaping, inode deletion, and wildcards—to safely remove such files on Linux systems.
This article analyzes why the Linux commands du and df often report inconsistent disk usage, detailing the underlying file system structures, inode and block allocation, how each tool gathers statistics, and the impact of mounted partitions and deleted-but‑still‑referenced files.
This guide shows how to increase the number of concurrent TCP connections on a Linux server by adjusting kernel parameters, expanding file descriptor limits, and understanding the underlying socket structures and lookup mechanisms that govern connection handling.
This guide provides a comprehensive, step‑by‑step walkthrough of Linux account security, user and shadow file inspection, login record analysis, process and startup script examination, cron job auditing, file integrity searches, and log‑based intrusion detection using practical commands and examples.
This guide explains how to use the Linux basename utility to strip directory paths and suffixes from filenames, covering its basic syntax, useful options like -z, -a, and -s, handling multiple files, removing extensions, and embedding it in shell scripts.
This guide walks through the complete process of adding a new disk to a Linux server running on VMware, including disk addition, partitioning, formatting, mounting, and handling disks larger than 2 TB with detailed command examples.
This guide details how to examine Linux user and shadow files, monitor login activity, investigate suspicious processes, review startup scripts, audit cron jobs, search for altered files, and analyze system logs to detect and mitigate potential intrusions.
This article introduces several essential Linux commands—including crypt (via mcrypt), various kill utilities, shred for secure deletion, zombie process identification, the at scheduler, and daemon management—explaining their purposes, usage examples, and relevant options for system administrators.
This guide explains practical techniques and command‑line tools—such as systemd‑detect‑virt, cgroup inspection, DMI data, and cloud‑provider metadata—to determine whether a given shell environment is running inside a container, a virtual machine, or on bare‑metal hardware, including scripts for Docker, rkt, AWS, OpenStack and more.
This article explores Linux’s TCP socket implementation, showing how to adjust system limits, dissecting key kernel structures like sock_common, and walking through the tcp_v4_rcv processing path and inet lookup functions, ultimately revealing methods to scale client connections beyond the traditional 65 535 port limit.
This guide explains how to optimize Linux kernel parameters and Nginx settings—such as file descriptor limits, TCP queue lengths, temporary ports, worker processes, KeepAlive, and log buffering—to significantly improve server performance and handle high traffic loads.
This guide shows how to download, extract, and run the lightweight nmon performance monitoring tool on CentOS 7, including the exact commands to fetch the package, choose the correct binary, start the utility, and view CPU and memory statistics using interactive keys.
This article explains the types and default actions of Linux signals, distinguishes between standard and real‑time signals, and demonstrates how to use the kill and trap commands with practical shell script examples for signal handling.
This guide explains how to become a professional software tester by covering test case creation, essential testing methods, protocol basics, when to adopt automation, key testing tools, UI and API automation scripting, SQL proficiency, and Linux basics for effective testing workflows.
This tutorial walks through extracting the MySQL 8.0.17 package, creating required directories and users, configuring my.cnf, initializing the data directory, setting up startup scripts, adding MySQL to the system PATH, starting the service, and securing the root password on a Linux host.
This guide presents a curated set of practical Linux command-line techniques for analyzing web server logs, including counting unique IPs, identifying popular pages, measuring traffic volume, detecting slow or error responses, and monitoring connection states, enabling administrators to efficiently monitor performance and security.
This guide walks through the concepts, volume types, environment setup, cluster creation, and client mounting steps required to build a highly available GlusterFS distributed replicated storage system integrated with NFS‑Ganesha on Linux servers.
This guide shows Linux administrators how to use the ps command with sorting and head to list the top ten processes by CPU usage, memory consumption, and virtual memory, explains the meaning of key ps output fields, and provides alternative sorting options.
This guide introduces ten fundamental Linux commands—pgrep, pstree, bc, split, nl, mkfifo, ldd, col, xmlwf, and lsof—explaining their purposes, typical usage examples, and how they help developers and system administrators efficiently manage processes, files, and system resources.
This tutorial explains MySQL benchmarking fundamentals and walks you through installing sysbench, configuring test parameters, preparing data, running the benchmark, analyzing results, and applying best‑practice recommendations to accurately assess database performance.
This guide shows Linux commands for quickly identifying the ten processes that consume the most CPU, memory, or virtual memory, explains the key ps fields, and provides alternative sorting options for system monitoring.
This article explains the true limits of concurrent TCP connections on a server, debunks common misconceptions about port numbers, details the TCP four‑tuple theory, outlines Linux file‑descriptor restrictions, shows how to tune kernel buffers with sysctl, and shares a real‑world test achieving one million active connections.
This article explains why detailed Linux system operation auditing is essential for security and troubleshooting, outlines practical filtering rules to avoid redundant or sensitive logs, and compares five auditing approaches—history, custom bash, snoopy, auditd, and eBPF—detailing their strengths, limitations, and configuration examples.
This guide explains how to list available shells, identify the current login shell, and use the chsh command to switch the default shell on a Linux system—covering changes to zsh or bash, verification steps, and accessing chsh help options.
The article explains why Linux’s du and df commands often report inconsistent disk usage, detailing the underlying file‑system structures such as inodes, block maps, and superblocks, the processes of file creation and deletion, and how mounted partitions, open file handles, and stat calls affect each tool’s calculations.
This article demystifies common misconceptions about server concurrency, explains the theoretical maximum TCP connections based on the four‑tuple, details Linux file‑descriptor and buffer limits, and walks through a practical experiment that achieves over one million simultaneous connections on a single machine.
The article explains how the Linux CFS scheduler balances load using three mechanisms—periodic balancer on busy CPUs, NOHZ idle balancer that wakes idle CPUs in tickless mode, and the new idle balancer that checks overload and cache state—detailing their triggers, IPI interactions, timing intervals, and key data structures.
This guide explains how to use rsync’s –exclude and –exclude‑from options, as well as include patterns and find‑based techniques, to selectively skip files or directories during synchronization, with clear command examples and practical tips.
This tutorial walks you through downloading Jenkins, setting up JDK 1.8, installing and configuring Supervisord, creating the Jenkins directory, configuring supervisord to manage Jenkins, retrieving the initial admin password, and completing the web UI setup, all with clear command examples and screenshots.
Auditing Linux system operations is essential for security and troubleshooting, but excessive logs can overwhelm analysis; this guide outlines common filtering rules and compares five recording methods—history, custom bash, snoopy, auditd, and eBPF—highlighting their advantages, limitations, and practical configuration examples.
This article explains the principles, use cases, and kernel implementation of Linux connection tracking (conntrack), covering its role in NAT, L4 load balancing, Netfilter hook mechanisms, key data structures, core functions, and performance considerations.
Learn how to use Linux's inotify-tools to monitor directory changes and automatically synchronize modified files with rsync, covering installation, command options, example output, an event‑handling shell script, and running the script in the background with nohup.
The article explains what inodes are, why they can become fully consumed even when disk space remains, how to monitor inode usage with df -i, and provides practical steps and command‑line scripts to locate offending directories, delete excess files, and prevent future inode exhaustion on Linux systems.
Utilization clamping (uclamp) lets user space specify a task’s minimum and maximum CPU utilization, allowing the Linux scheduler to more accurately scale frequency and select cores, improving performance and power efficiency through per‑task, cgroup, and global APIs that replace the older schedtune mechanism.
The article explains why a client can successfully write to a TCP socket after the server has closed its end, why the first write succeeds while the second fails, and how Linux kernel code and TCP state transitions cause this behavior.
This comprehensive tutorial walks you through why Linux matters, how to install VMware, create and configure a CentOS VM, set up networking, use Xshell, master essential commands, manage users, install software via source, RPM or YUM, and write functional Bash scripts with practical examples.
This comprehensive guide explains the Linux filesystem hierarchy, the purpose of the Filesystem Hierarchy Standard, the roles of top‑level directories such as /, /usr and /var, the differences between absolute and relative paths, common file types, extensions, and how to interpret file attributes using standard commands.
This article traces Linus Torvalds' journey from studying operating systems with Minix to creating the Linux monolithic kernel, highlighting the historical context, technical choices, community collaboration, GNU involvement, and the factors that propelled Linux to dominate modern computing.
This guide details Linux account security fundamentals, including critical system files, user and privilege inspection commands, login monitoring, intrusion investigation techniques, startup script analysis, cron job auditing, file searching methods, process inspection, and log file examination to help secure and troubleshoot Linux servers.
This comprehensive guide covers the fundamentals of processes and threads, their definitions, relationships, creation, lifecycle, scheduling strategies, context switching, inter‑process communication methods, and practical C/C++ examples, providing a deep dive into operating‑system concepts for developers and interview preparation.
This guide explains how to interpret the Linux free command, distinguishes between used, free, buffers, and cache memory, describes common symptoms of memory pressure, and provides step‑by‑step commands to manually clear swap and drop caches for better system performance.
This guide explains what SSH (Secure Shell) is, why it’s essential for encrypted communication and Linux server access, and provides a concise overview of OpenSSH’s core concepts and basic commands, serving as a quick reference manual for users.
This article details a network outage caused by ARP cache state transitions, neighbor reachability detection differences between Linux 6.0/7.0, Cisco NXOS ARP timeout, and keepalived standby handling, explaining how these factors led to traffic disruption and the eventual root‑cause resolution.
This article explains how Linux implements the TCP/IP model to encapsulate, transmit, and receive network packets, covering OSI vs TCP/IP layers, the Linux network stack structure, NAPI interrupt mitigation, and the step‑by‑step processing of packets in both directions.
Explore the evolution of Containerd from Docker’s early days, its architecture, installation on Ubuntu, configuration nuances, performance benchmarks, and practical usage with the ctr CLI, while also learning how it integrates with Kubernetes, Docker, and tools like Sealos for streamlined container management.
This guide explains how to batch‑install Docker on Linux servers by creating a deployment directory, writing an Ansible playbook that unpacks the Docker binary, copies the service file, configures systemd, and verifies the installation with Docker commands.
This guide provides a concise reference of curl's most useful command‑line options, explaining how to customize headers, handle cookies, send data, manage redirects, control output, and debug requests for efficient web and API interactions.
This article provides a comprehensive overview of the evolution of operating systems, analyzes the rise of Chinese domestic OS such as Kylin, Deepin and HarmonyOS, examines market share trends across desktop, server and mobile platforms, and forecasts the economic potential of government, enterprise and consumer adoption over the next five years.
Learn how to efficiently switch between directories in Linux using the built‑in bash commands pushd, popd, and dirs, covering basic usage, stack manipulation, and advanced options to eliminate repetitive typing and streamline your workflow.
This guide explains how to safely back up and restore a Linux system using tar archives, rsync synchronization, dd cloning, and full-disk imaging, covering command syntax, exclusion of volatile directories, preparation steps, and post‑restore configuration to ensure a reliable recovery.
This comprehensive cheat‑sheet covers essential Linux commands for viewing system information, managing files and directories, handling users and groups, controlling permissions, mounting filesystems, performing backups, and using package managers like RPM, YUM, DEB and APT, plus networking and CD/DVD utilities.
This article provides a comprehensive reference of essential Linux system commands covering system information, date and time management, shutdown/reboot, file and directory operations, searching, mounting, disk usage, user and group management, permissions, special attributes, compression, package handling, network utilities, and backup techniques, all presented with concise examples for quick learning.
This guide explains how to back up an entire Linux system or create a disk image using tar, rsync, and dd commands, covering exclusion of system directories, restoration steps, and special considerations for migrating to a new host.
This guide explains what strace is, how to use it for filtering system calls, profiling execution time, diagnosing configuration issues, and tracing network activity, providing concrete command examples and interpretation of output to help troubleshoot Linux processes efficiently.
The article explains the relationship and distinctions among 32‑bit and 64‑bit concepts across hardware, operating systems, and software, detailing Intel and AMD architectures, how to identify CPU and OS bitness on Linux, and the implications for compiling kernels and running applications.
