This guide explains multiple Linux techniques—including nologin shells, sshd_config allow/deny lists, and hosts.allow/hosts.deny rules—to prevent selected users, groups, or IP addresses from logging in via SSH, with practical commands, examples, and a ready‑to‑run script.
This article reviews Linux virtual memory layouts for 32‑bit and 64‑bit systems, explains the kernel and user address spaces, details how threads consume stack memory, and outlines both virtual‑memory and kernel‑parameter limits that affect the maximum number of threads a process can create.
This guide maps Linux kernel subsystems to key performance metrics and presents a curated set of CPU, memory, disk I/O, and network tools—complete with visual charts, metric explanations, and practical notes for effective system analysis.
This guide walks you through key Linux commands such as top, free, iostat, netstat, df, and du, explaining each output field, how to interpret system load, memory usage, CPU statistics, network connections, and disk space to quickly diagnose production issues.
This guide walks through enabling the Ceph NFS manager module, creating an NFS cluster, exporting a CephFS directory via NFS, mounting it from a client, verifying data consistency, and configuring high‑availability for the nfs‑ganesha service using haproxy and keepalived.
This guide explains how to fine‑tune Linux kernel settings—including sysctl network parameters, shared memory limits, local port ranges, and disk scheduler options—using configuration files and command‑line tools to improve system stability and throughput.
When multiple CentOS 7 servers in the same rack experience 30‑60 second delays before prompting for an SSH password, the slowdown is usually caused by reverse DNS lookups and GSSAPI authentication, which can be resolved by disabling UseDNS and GSSAPIAuthentication in sshd_config and restarting the service.
This tutorial explains the Linux join command for merging two files based on matching key fields, covering syntax, common options like -a, -e, -i, -o, -t, -v, -1, -2, and provides practical examples with sample file contents and command outputs.
This guide introduces ShellCheck, a static analysis tool for Linux shell scripts, outlines its key features, shows how to install it on various distributions or use it online, demonstrates command‑line usage with a practical example, and explains integration with editors like VSCode.
This guide explains multiple techniques—nohup, disown, setsid, tmux, screen, and at—to run scripts in a Linux environment so they continue executing after the user logs out, providing command examples, usage details, and a comparison of terminal multiplexers for reliable background processing.
This guide explains the KDUMP mechanism in Linux, walks through configuring a crash kernel, setting up the KDUMP service, verifying the setup, and using the crash utility to analyze memory dumps with detailed command examples and practical use cases.
An introductory guide to Linux's man command explains its sectional organization, configuration file, essential navigation shortcuts, bookmarking, shell execution, and useful options like -a, -aw, -M, -k, and -f, helping users efficiently access and search manual pages.
This article explains how Ceph cache pools work, compares read‑only and write‑back cache types, provides step‑by‑step commands for creating and configuring cache pools, adjusting CRUSH rules to target SSDs, and outlines safe removal procedures for both cache modes.
Linux 6.10 adds a new DRM Panic infrastructure that displays a blue‑screen‑of‑death style message on kernel crashes, supporting drivers like SimpleDRM, MGAG200, IMX and AST, while systemd‑255 introduces an experimental systemd‑bsod component for emergency error reporting.
This guide walks through installing iptables, loading kernel modules, starting the firewall, mastering core iptables options, creating and managing rules for ports, IPs, and protocols, saving configurations, troubleshooting pitfalls, and provides hands‑on exercises for Linux network security.
This tutorial explains the fundamentals of DNS, introduces BIND components, walks through installing the bind package, configuring named.conf and zone files for forward and reverse lookups, adjusting network settings, and testing the DNS server on a Linux host.
Linux 6.10 adds a new DRM Panic infrastructure that displays a BSOD‑style screen on kernel crashes, supporting drivers like SimpleDRM, MGAG200, IMX and AST, while systemd‑255 introduces an experimental systemd‑bsod component for full‑screen emergency messages, offering a clearer way to diagnose panics.
This article explains the concepts, reasons, and implementation methods of Linux kernel synchronization, covering mutual exclusion, various lock types, compiler and memory barriers, atomic operations, semaphores, read‑write semaphores, and spinlocks with illustrative code examples and usage guidelines.
This guide explains the principles of MD5 and SHA‑512 checksums, demonstrates how to generate and compare them using Linux commands such as md5sum and sha512sum, and shows how to automate integrity verification for files like calico.yaml during transfer or backup.
This guide explains how to use ifconfig to view and modify network interfaces, manage them with ifup/ifdown, edit CentOS 7 configuration files, apply additional ip commands, and troubleshoot common VM cloning network issues.
This article walks through a real Linux kernel hard lockup case, explaining what hard lockup is, analyzing stack traces and register values, identifying a spinlock contention on a per‑CPU runqueue, and showing how an inappropriate GFP flag caused interrupts to be enabled at the wrong time, leading to a deadlock and the eventual fix.
This article explores essential Linux I/O techniques, covering basic file operations with system calls like open, read, write, and close, advanced methods such as memory‑mapped files and asynchronous I/O, network programming with sockets and multiplexing, plus performance‑tuning strategies for efficient resource utilization.
To handle high‑traffic web workloads, the default Linux kernel settings must be adjusted; this guide explains the key sysctl parameters—such as file‑max, tcp_tw_reuse, tcp_keepalive_time, and buffer sizes—and how to apply them for optimal Nginx concurrency.
This guide explains the concepts of network bandwidth, shows how to check physical and virtual NIC speeds on Linux using ethtool, dmesg, and mii‑tool, demonstrates real‑world throughput testing with iperf3, and provides tips for identifying network bottlenecks.
This guide walks through preparing three CentOS 7 nodes, installing Erlang and RabbitMQ, configuring users and permissions, setting environment variables, enabling the management plugin, synchronizing erlang.cookie, joining nodes in RAM or disc mode, and verifying cluster status via the web UI.
This guide walks you through preparing a Ceph cluster, enabling the NFS module, creating an NFS service with nfs‑ganesha, exporting a CephFS share, mounting it from a client, and configuring high‑availability using HAProxy and keepalived.
The article details the complete process of porting QQ's NTRTC audio/video SDK to Linux, covering platform surveys, packaging, build‑time issues like GLIBC mismatches and fPIC errors, debugging steps, Qt/Electron demos, GPU blocklist workarounds, and future compatibility plans.
This article explains the Linux thundering herd phenomenon, its impact on processes, threads, and epoll, demonstrates it with C code examples, analyzes system overhead, and presents mitigation techniques such as accept mutex, SO_REUSEPORT, and proper locking to improve server performance.
This guide explains Linux file permission concepts—including owner, group, and others—covers read, write, and execute rights, demonstrates how to view permissions with ls -l, and provides detailed usage of chmod and chown commands with symbolic and numeric modes.
This guide walks through setting up a Linux server and client, installing hping3 and netcat, and using them to reliably detect whether specific UDP ports are open or closed, including command examples, expected outputs, and troubleshooting tips.
This guide explains what rsync is, walks through cross‑compiling it for an ARM board, shows how to install the binary, and demonstrates practical file‑synchronization commands with detailed flag explanations.
This article explains common scenarios that cause MySQL or Java processes to consume 900% CPU, walks through step‑by‑step diagnosis using Linux tools, and provides concrete optimization techniques such as indexing, caching, thread analysis, and code adjustments to bring CPU usage back to normal levels.
An in‑depth comparison of PostgreSQL and MySQL covers their histories, ACID compliance, performance, scalability, advanced features, security, backup strategies, installation on Linux, and provides practical SQL code examples to help full‑stack developers choose the right open‑source relational database for their projects.
This guide walks through SSH secure tunneling techniques—including local, remote, and dynamic port forwarding—detailing command syntax, option usage, binding address considerations, and practical examples for accessing otherwise unreachable services through encrypted tunnels.
This article compiles several Zhihu contributors' insights explaining why Linux dominates modern server environments, covering historical Windows dominance, IIS shortcomings, licensing costs, ecosystem advantages, container support, and the broader shift toward open‑source infrastructure.
This article explains how to use the htop command to monitor CPU, memory, load average, uptime, and detailed process information in real time, and provides a full reference of its interactive keyboard shortcuts for efficient system management.
This article explains the fundamentals of VXLAN, compares it with VLAN, and provides step‑by‑step Linux kernel and Open vSwitch implementations, including configuration commands, packet‑flow analysis, and practical testing to demonstrate overlay networking in cloud environments.
German Linux‑hardware maker TUXEDO unveiled its ARM‑based “Drako” laptop at Computex, featuring a Qualcomm Snapdragon X Elite 12‑core CPU, 14‑inch 2560×1600 IPS display, 32 GB LPDDR5x RAM and PCIe Gen4 SSD, running the KDE‑Plasma TUXEDO OS ported to ARM, with Qualcomm’s upstream Linux support and collaborations with Lenovo, Arm and Linaro, and the first units slated for delivery by the end of 2024.
This guide explains the physical structure of mechanical hard drives, how data is organized into sectors, tracks, and cylinders, and provides step‑by‑step Linux commands for calculating disk capacity, creating MBR/GPT partitions, formatting filesystems, and managing swap space.
This guide explains Linux routing commands for adding host and network routes, setting default gateways, creating permanent static routes via rc.local, sysconfig files, and static‑routes, enabling IP forwarding, and demonstrates a dual‑NIC experiment using VMware and eNSP to achieve simultaneous internal and external network access.
Learn how to install Apache from source, understand its three MPM modes (prefork, worker, event), configure common server settings, set up port‑ and domain‑based virtual hosts, and deploy both static and dynamic (LAMP) websites with step‑by‑step command examples.
This article introduces RAID fundamentals, compares common RAID levels (0, 1, 5, 10), explains their performance and fault‑tolerance characteristics, and provides step‑by‑step Linux mdadm commands to create, inspect, and manage a RAID‑5 array, including simulating disk failures and recovery.
This guide presents twenty practical Linux command‑line shortcuts—from tab completion and directory navigation to history search and log monitoring—that help both beginners and seasoned users work faster, avoid common pitfalls, and streamline everyday terminal tasks.
This guide explains firewall fundamentals, classifications, and detailed usage of Linux iptables and firewalld commands, covering tables, chains, rule priorities, NAT/ SNAT examples, and zone-based configurations to help secure network traffic effectively.
This article explains the Linux OOM (Out‑Of‑Memory) mechanism, details how the kernel selects and kills the most memory‑hungry process, and shows practical steps to protect critical services from being terminated.
This guide walks through the complete Linux startup sequence, covering power‑on initialization, BIOS/UEFI boot, MBR/GRUB2 loading, kernel entry, init processes, ramdisk handling, run‑level configuration, fstab mounting, and user login mechanisms, illustrated with diagrams and key command references.
This guide explains why accidental database deletion is a serious risk, outlines essential permission and logging measures, and provides step‑by‑step scripts and cron jobs to automatically back up MySQL databases and critical files using Docker, OpenSSL, rsync, and expect.
This tutorial explains the Linux xargs command and provides six practical, step‑by‑step examples—including copying files, deleting by extension, compressing directories, renaming to uppercase, counting lines, and listing user accounts—to help automate common system tasks efficiently.
This guide explains how to configure both permanent and temporary environment variables on Linux for different shells (bash and csh), covering user‑specific and system‑wide settings, the required configuration files, and the exact commands to apply and verify the changes.
This guide explains how to use the Linux route command to display the IP routing table, install the necessary net‑tools package, and perform common operations such as adding, deleting, and blocking routes, including options for persistence and detailed output interpretation.
This guide walks through Linux primary and logical partition concepts, MBR structure, fdisk commands, creating and formatting partitions with XFS, automating mounts, handling large or faulty disks, and setting up swap space for virtual memory.
The article walks through the Flash Friendly File System’s on‑disk layout—zones, sections, segments, blocks, SuperBlock, checkpoint, SIT, NAT, and SSA—showing how formatting, mounting, creating, modifying, and deleting files updates these structures, offering a practical guide for kernel and storage engineers.
The article explains how to configure static and persistent routes on a Linux host using the route command, make them survive reboots via rc.local, sysconfig files, or sysctl, enable IP forwarding, and demonstrates a dual‑NIC experiment where a single static route lets the client access both external and multiple internal subnets.
This guide walks through installing Ansible via source, git or RPM, configuring its environment and SSH trust, adding hosts to the inventory, and testing connectivity with ping, providing essential commands and examples for effective automation on CentOS systems.
This article compiles over a thousand interview questions for operations engineers, covering operations fundamentals, Kubernetes, shell scripting, Linux, Docker, Jenkins, databases, and more, providing a comprehensive study guide for anyone preparing for DevOps or system administration roles.
This article explains Linux's page reclamation process, describing how the kernel recovers memory under pressure using PFRA, LRU algorithms, direct reclaim, compaction, and OOM handling, and provides detailed source code analysis of the involved kernel functions.
This guide explains Linux routing commands for adding host and network routes, setting default gateways, deleting routes, making routes permanent via rc.local, sysconfig files, and IP forwarding, and demonstrates a dual‑NIC experiment using VMware and eNSP to connect internal and external networks with step‑by‑step verification.
This guide walks you through installing Ansible on Linux, configuring inventory and settings, writing a basic playbook to deploy a web server, and executing it, while also covering variables, roles, templates, handlers, conditional tasks, and error handling for robust automation.
This article warns about ten extremely dangerous Linux commands—such as rm ‑rf, fork bombs, and disk‑wiping operations—explaining their destructive effects, how they work, and practical safeguards like using aliases or testing only in virtual machines to prevent catastrophic data loss.
This guide explains step‑by‑step how to install the GeoIP2 library, compile Nginx with the ngx_http_geoip2 module, download the MaxMind GeoLite2 database, configure Nginx to map country codes, and block non‑Chinese visitors by returning a 404 response.
This comprehensive guide introduces the 100 most frequently used Linux shell commands, covering file, directory, permission, network, process, system, and scripting operations with clear explanations and practical examples, helping both beginners and professionals improve efficiency and mastery of the command line.
This article explains the Linux /proc virtual filesystem, the special role of /proc/self for accessing the current process's information, and provides practical commands to read cmdline, cwd, exe, environ, maps, and mem files for system monitoring and debugging.
The article explains Linux kernel reverse‑mapping (RMAP), describing its purpose for efficient page‑reclaim, the underlying data structures such as vm_area_struct, anon_vma and anon_vma_chain, and shows how anonymous and file pages are tracked and unmapped through detailed code examples.
This tutorial explains how to capture live video from a camera with PHP, install necessary Linux drivers, extract frames using FFmpeg, and apply the Fer2013 emotion‑recognition model through a Python script to infer human emotions in real time.
This guide shows how to use df, du, find, and lsof commands to locate large directories, files, and deleted-but-open files that consume disk space, and explains how to adjust reserved filesystem space on Linux.
An inode is a crucial Unix/Linux filesystem structure that stores file metadata, links files to data blocks, and enables features like hard and soft links; this guide explains its role, composition, related commands, and how inode exhaustion can affect system storage.
Linux dominates modern server environments because its free, lightweight distributions and robust open‑source ecosystem outperform the costly, configuration‑heavy Windows/IIS stack, offering superior performance, native container support, and community‑driven innovation that overcame early Microsoft resistance and drove industry-wide adoption.
This guide explains what sersync is, its main features and use cases, and provides step‑by‑step instructions—including server preparation, rsync daemon setup, configuration files, password handling, and command examples—to deploy a real‑time file synchronization service on Linux.
This guide explains how to use the Linux df command with various options to display filesystem disk space, inode usage, and filesystem types in human‑readable, kilobyte, megabyte, or gigabyte formats, and shows how to filter or exclude specific filesystem types.
This guide explains how LVM snapshots work, how to create them using copy‑on‑write, restore individual files or entire volumes, merge snapshots back into the original LV, and leverage snapshots for testing environments, all without stopping services.
This article introduces Linux's file system concepts, covering the unified view of resources as files, the hierarchical directory layout, the role of inodes in mapping logical to physical storage, and the differences between hard and soft links.
This guide explains how to install the open‑source ClamAV antivirus on Linux, update its virus definitions, run recursive scans with various options, and automate deployment using Ansible, providing practical commands and sample outputs for effective malware protection.
This article compiles several Zhihu answers that trace the historical shift from Windows/IIS to Linux-based servers, highlighting ecosystem dynamics, cost advantages, performance differences, container support, and open‑source adoption that together explain why Linux dominates modern server environments.
This guide explains how to use the lsof command on Linux to list open files, filter by process, directory, user, or network criteria, combine options, view UNIX domain sockets, count open files, and even recover accidentally deleted files using file descriptors.
This guide explains why a simple sudo command may still produce a Permission denied error when redirecting output to a file you lack write access to, and presents four practical methods—including running a shell with sudo, using scripts, sudo -s, and sudo tee—to successfully write to such protected files on Ubuntu 18.04.
This article investigates two real‑world performance incidents—one caused by excessive disk I/O from a misconfigured Filebeat and another by kernel memory‑fragmentation bugs triggered by a trace feature—detailing observations, Linux diagnostic commands, analysis, and practical remediation steps.
This article explains the fragmentation problems of the Linux slab allocator, introduces the zsmalloc memory allocator and its requirements, surveys mainstream kernel memory‑compression techniques such as zSwap, zRAM and zCache, and details related allocators like Zbud and Z3fold with example source code.
Learn to create a Bash script that backs up a specific MySQL database using mysqldump, automatically deletes old backups, handles Windows line‑ending issues, schedules daily execution with cron, and restores compressed backups, complete with detailed command examples and explanations of find -mtime.
This comprehensive guide explains how to use essential Linux monitoring commands—including top, free, vmstat, iostat, mpstat, sar, netstat, uptime, ps, watch, strace, and lsof—detailing their purpose, key options, output fields, and practical examples to help you diagnose system performance and resource usage.
This article provides a comprehensive overview of the Linux kernel memory management subsystem, covering its hardware architecture, address‑space layout, various memory zones, and the software structures for page and object allocation and reclamation.
This guide provides a concise reference of essential Linux commands for file and directory handling, file operations, permission management, searching, process control, networking, system monitoring, hardware information, log handling, text processing, and package management on both Debian‑based and RPM‑based distributions.
This article explains how Linux processes inherit and use real, effective, and saved user IDs to enforce permission checks, covering the login sequence, UID inspection via /proc, set‑uid behavior, and the execution flow of external commands and shell scripts.
This guide explains what a default gateway is, how to set it manually on Linux, and how to handle single, dual, or triple NIC configurations using route and iproute2 commands, including creating separate routing tables, static routes, and bonding for redundancy and load balancing.
This guide explains how to effectively manage application logs on Linux by defining log content and archiving rules, handling special cases for services like MySQL and nginx, using crontab for scheduled cleanup, and configuring logrotate with detailed options and examples.
This comprehensive guide walks you through Linux container fundamentals, Docker architecture, image lifecycle, command‑line operations, volume handling, Dockerfile creation, network configurations, registry setup, Docker‑Compose orchestration, and best practices for production‑grade container deployments.
This guide walks through setting up a complete CI/CD environment on three CentOS 7.6 machines—GitLab, Jenkins, and Tomcat—covering installation, configuration, plugin management, Maven integration, SonarQube scanning, and automated deployment of a Java web application.
Linux system performance depends on CPU, memory, disk I/O, network, kernel parameters, and hardware, and troubleshooting requires comprehensive checks using tools like top, vmstat, iostat, netstat, perf, and sysctl, with step‑by‑step guidance for identifying bottlenecks, optimizing resources, and tuning TCP settings.
This article explains why the Linux find command is essential for operations, walks through an interview question about deleting year‑old logs, and then details eight practical find usages—including name patterns, file types, timestamps, sizes, permissions, ownership, executing actions, and directory searches—complete with example commands.
This article compiles over a decade of real‑world Oracle single‑instance and RAC deployment experiences, detailing compatibility issues, specific bugs encountered in versions 10g, 11g, 12c, 19c on Linux platforms, and step‑by‑step remediation commands, scripts, and configuration adjustments to ensure successful installation.
This tutorial walks you through expanding a Linux disk from 500 GB to 2 TB using fdisk, resizing the ext4 filesystem with resize2fs, remounting the partition, and configuring persistent auto‑mounts via /etc/fstab, rc.local, systemd, or autofs, while also covering common error fixes.
This guide introduces Atuin, an SQLite‑backed shell history enhancer, explains its key features, shows how to install it on Linux, configure syncing, and demonstrates powerful commands for searching, statistics, and importing existing history.
This guide explains how to use the md5sum command to generate and compare file checksums, save them for later verification, employ options like -c, --quiet, and --status, and script batch integrity checks on Linux systems.
This guide walks you through installing NFS on CentOS 7, creating a shared directory, configuring export options, starting the service, and then configuring a client to automatically mount the share using /etc/fstab, with verification steps included.
This guide explains how to install ClamAV on Linux via EPEL, update its virus definitions, perform recursive scans with clamscan, interpret scan results, and automate deployment using Ansible, while also comparing alternative scanners such as Comodo, Armadito, and ClamTK.
This guide details how to configure Linux services for automatic boot startup using systemd (systemctl), the legacy chkconfig method, generic script approaches, and crontab @reboot syntax, plus best‑practice recommendations for production environments.
Zero‑copy is an optimization technique that eliminates unnecessary memory copies between kernel and user space by leveraging DMA, memory‑mapping and specialized system calls, thereby reducing CPU load, latency and improving throughput for high‑performance networking, storage and multimedia workloads.
This comprehensive guide introduces Wireshark and Tcpdump, explains their installation, core features, common use cases, filter syntax, interface components, and step‑by‑step examples—including TCP three‑handshake analysis—empowering IT professionals to capture and analyze network traffic efficiently.
This guide walks through the complete PXE boot process, explains how Cobbler extends PXE with automated DHCP/TFTP management, and provides detailed commands and configuration examples for installing Cobbler, fixing common issues, importing a local ISO, creating kickstart files and profiles, and finally launching a fully automated OS installation.
This article explains the concept of MySQL master‑slave replication, outlines its advantages and drawbacks, and provides a step‑by‑step guide—including downloading MySQL 8.0, configuring my.cnf on master and slave servers, creating replication users, setting up replication parameters, and using Laravel for read‑write splitting—complete with all necessary shell and SQL commands.
The article explains how Linus Torvalds practices "dogfooding" by regularly building and testing the Linux kernel on his own hardware, describes the concept of dogfooding in software development, and details the specifications of his primary development PC and secondary MacBook Air laptop.
