Linux terms
The operating system underneath almost everything in production
Linux runs the servers, containers, and cloud instances that power most production software. This category covers shell commands, file systems, process management, permissions, networking tools, cron jobs, and the system internals that every backend developer benefits from understanding. Knowing your way around Linux is not optional when something breaks at 2am.
More on Linux
History
Linux originated in 1991 when Linus Torvalds released the first kernel as a free, open-source alternative to proprietary Unix systems, building on the GNU project's free software tools and utilities. Throughout the 1990s and 2000s, Linux evolved from a hobbyist project into a production-grade operating system, gaining adoption in server environments, embedded devices, and eventually consumer applications through distributions like Red Hat, Debian, and Ubuntu. Key milestones included the stabilization of the kernel API, the rise of Linux in data centers and cloud infrastructure, and the development of standardized tools for process management, networking, and system administration. Modern Linux practice emphasizes containerization (Docker, Kubernetes), infrastructure-as-code, and automated operations, while the kernel itself continues to incorporate advanced features like namespaces, cgroups, and eBPF for security and performance. Today, Linux powers the majority of servers, cloud platforms, mobile devices via Android, and embedded systems worldwide, making it foundational to contemporary software development and DevOps practices.
Key concepts
- Linux File Permissions
- Linux File System Hierarchy
- Linux Processes
- Environment Variables
- Shell Pipes & Redirects
- Bash Scripting
- Linux User & Group Management
- Linux Networking Tools
Best references
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The Linux Kernel Documentation Official kernel documentation covering namespaces, cgroups, memory management, and file systems—the authoritative source for low-level Linux internals.
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GNU Coreutils Manual Comprehensive reference for core Unix utilities including file permissions, shell pipes, redirects, and command-line tools essential to Linux system administration.
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The Linux Programming Interface by Michael Kerrisk Seminal book and companion website covering system calls, file descriptors, processes, memory management, and networking—widely regarded as the definitive Linux systems programming reference.
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Systemd Official Documentation Authoritative source for systemd services, unit files, and modern init systems—essential for understanding service management on contemporary Linux distributions.
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Linux man-pages Project Central repository for Linux manual pages covering system calls, library functions, file formats, and utilities—the canonical reference for CLI tools and system interfaces.
✦ Latest in Linux
Typed relationships here
Edges touching a Linux term.
- Environment Variables Often seen in Cron Jobs 2d
- Linux Performance Tools Measures Linux Memory Management 2d
- Cron Jobs Often seen in Linux Log Files 5d
- Linux User & Group Management Precedes Linux File Permissions 5d
- Linux User & Group Management Mitigates Privilege Escalation 5d
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iptables and netfilter
Kernel packet-filtering framework (netfilter) and its classic userspace tool (iptables) for firewalling, NAT, and packet mangling.
5d ago
linux advanced
Linux Namespaces
Kernel feature that isolates global resources (PIDs, network, mounts, IPC, hostname, users) so processes see their own private view of the system.
3w ago
linux advanced
cgroups — Linux Control Groups
A Linux kernel feature that groups processes and meters or limits their access to CPU, memory, I/O, network, and other resources — the core primitive that makes Docker, systemd, and Kubernetes resource limits possible.
2mo ago
linux advanced
Linux File Permissions
1
Read, write, and execute permissions assigned to owner, group, and others — the foundation of Linux access control for web application files.
CWE-732 OWASP A5:2021
2mo ago
linux beginner
7.5
Memory-Mapped Files
A file mapped directly into a process's virtual address space — reads and writes go through the OS page cache rather than read()/write() syscalls, enabling fast access to large files and shared memory between processes.
2mo ago
linux advanced
Environment Variables
PHP 5.0+
1
Key-value pairs inherited by child processes — the standard way to pass configuration, credentials, and runtime settings to PHP applications without hardcoding.
3mo ago
linux intermediate
File Descriptors & ulimit
PHP 5.0+
File descriptors are integer handles for open files, sockets, and pipes — each process has a limit (ulimit -n), and exhausting them causes 'too many open files' errors.
3mo ago
linux intermediate
Linux Log Files
2
Log locations, rotation, and analysis tools on Linux — /var/log/ structure, journald, logrotate, and essential log analysis commands.
3mo ago
linux intermediate
Linux Memory Management
1
How Linux allocates RAM — virtual memory, the page cache, swap, and the OOM killer — and what PHP developers need to know when PHP processes run out of memory.
3mo ago
linux intermediate
Linux Networking Tools
PHP 5.0+
Essential tools for diagnosing network issues on Linux servers — ss, netstat, curl, dig, tcpdump, and ping each reveal different layers of connectivity problems.
3mo ago
linux intermediate
Linux Package Managers
apt (Debian/Ubuntu), yum/dnf (RHEL/CentOS/Fedora), apk (Alpine) — tools for installing, updating, and managing system software packages and their dependencies.
3mo ago
linux beginner
Linux Performance Tools
1
Essential tools for diagnosing CPU, memory, IO, and network performance on Linux — top, htop, vmstat, iostat, perf, strace, and ltrace.
3mo ago
linux intermediate
Linux User & Group Management
2
Managing users and groups on Linux servers — useradd, usermod, passwd, groups — and best practices for PHP web server user isolation and privilege separation.
3mo ago
linux intermediate
Regex with grep, sed & awk
Three essential Linux text processing tools — grep for filtering lines, sed for stream editing, awk for field-based processing — all using regular expressions.
3mo ago
linux intermediate
Systemd Services & Unit Files
Systemd is the init system managing service lifecycle on modern Linux — unit files define how services start, stop, restart, and depend on each other.
3mo ago
linux intermediate
Bash Scripting
bash4
1
Writing shell scripts in Bash to automate command-line tasks — from simple file operations to complex deployment pipelines.
3mo ago
linux intermediate
Cron Jobs
PHP 5.0+
3
Scheduled tasks defined in a crontab file, executing commands at specified time intervals — from once a minute to once a year.
3mo ago
linux beginner
Linux File System Hierarchy
1
The standard directory structure of Linux — /etc for config, /var for variable data, /tmp for temporary files, /usr for user programs — knowing it prevents misplacing files.
3mo ago
linux beginner
Linux Processes
PHP 5.0+
Every running program is a process with a PID, memory space, and file descriptors — ps, top, kill, and signals are the essential tools for managing them.
3mo ago
linux intermediate
Shell Pipes & Redirects
Pipes (|) connect stdout of one command to stdin of another; redirects (<, >, >>) send stdin/stdout to files — the foundation of composable Unix command-line workflows.
3mo ago
linux intermediate