Linux Process Management Cheat Sheet

Updated 2026-05-20

Next Topic: Linux Text Processing with grep, sed, and awk Cheat Sheet

🧠Study flashcards on this topic129 cards · spaced repetition→

Linux process management is the set of tools and techniques for inspecting, controlling, and tuning the processes running on a Linux system. Every running program — a web server, a shell, a background cron job — exists as a process with its own PID, memory footprint, scheduling attributes, and signal-response rules. Mastering process management is a core sysadmin and developer skill: it lets you diagnose performance problems, clean up runaway jobs, tune CPU and I/O priority for competing workloads, and write scripts that run reliably even when users disconnect. The non-obvious key insight is that signals are the universal control channel — understanding which signal to send (and when) separates a practitioner from someone who always reaches for kill -9.

What This Cheat Sheet Covers

This topic spans 19 focused tables and 168 indexed concepts, 129 flashcards. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.

Table 1: Process Listing with psTable 2: Process State Codes (STAT Column)Table 3: Finding Processes with pgrep and pidofTable 4: Linux Signals ReferenceTable 5: Sending Signals with kill, pkill, and killallTable 6: CPU Priority with nice and reniceTable 7: I/O Priority with ioniceTable 8: Background Execution and Job ControlTable 9: Process Tree Visualization with pstreeTable 10: Tracing System Calls with straceTable 11: Listing Open Files with lsofTable 12: Resource Limits with ulimitTable 13: The /proc Filesystem for Process InspectionTable 14: CPU Affinity and Real-Time SchedulingTable 15: OOM Killer and Memory ProtectionTable 16: Zombie and Orphan ProcessesTable 17: Signal Trapping in Shell ScriptsTable 18: Performance Profiling with perfTable 19: Cgroup-Based Resource Control

Quick IndexSubscribe to unlock

A jump-to index of every table row in this cheat sheet.

Mind MapSubscribe to unlock

An interactive map of every table and concept in this topic.

Table 1: Process Listing with ps

The ps command is the go-to snapshot tool for seeing what is running on a system. BSD-style (ps aux) and POSIX-style (ps -ef) produce similar output but differ in columns — aux adds %CPU, %MEM, VSZ, RSS, and STAT, while -ef adds PPID (parent PID).

Command	Example	Description
ps aux	`ps aux`	Lists all processes for all users with CPU%, MEM%, VSZ, RSS, and STAT columns (BSD style).
ps -ef	`ps -ef`	Lists all processes in full format including PPID (POSIX/UNIX style).
ps -eo (custom columns)	`ps -eo pid,ppid,ni,pcpu,pmem,comm`	• Prints only the user-specified columns • any keyword from `ps --help all` is valid
ps --sort	`ps -eo pid,pcpu,comm --sort=-%cpu`	• Sorts output by a field • prefix with `-` for descending order (e.g. top CPU consumers first).
ps -C (by command name)	`ps -C nginx -o pid=`	• Selects processes by exact executable name • suppresses header with `=`.
ps -p (by PID)	`ps -p 1234 -f`	Shows full info for a specific PID.
ps --ppid (children)	`ps --ppid 1234`	Lists all direct child processes of a given parent PID.
ps --forest	`ps -ef --forest`	Draws an ASCII tree of parent–child relationships.
ps -L (threads)	`ps -L -p 1234`	Adds an LWP (thread ID) column to show all threads inside a process.
ps -u / -U (by user)	`ps -u www-data`	Filters output to processes owned by a specific user (effective UID with `-u`, real UID with `-U`).

Table 2: Process State Codes (STAT Column)

The STAT column in ps encodes the current kernel state of a process. Understanding these codes is essential for diagnosing stuck, zombie, or runaway processes. A second letter (modifier) often appears alongside the primary code.

Code	Example	Description
R (running)	`STAT: R`	Process is running or runnable — on the CPU or queued for it.

The rest of this section is part of the full cheat sheet

Table 3: Finding Processes with pgrep and pidof

pgrep and pidof offer fast, scriptable ways to find PIDs without piping ps through grep. pgrep matches against process names (and optionally full command lines), while pidof does exact binary-name lookup. Both return just PIDs, making them easy to feed into kill or renice.

Command	Example	Description
pgrep (basic)	`pgrep nginx`	Returns PIDs of all processes whose name matches the pattern.

The rest of this section is part of the full cheat sheet

Table 4: Linux Signals Reference

Signals are software interrupts sent to processes by the kernel, other processes, or the user. Most process control — from graceful shutdown to forced termination to config reload — is done via signals. Run kill -l to list all signals on your system.

Signal	Example	Description
SIGTERM (15)	`kill 1234`	• Default signal from `kill` • requests graceful termination — process can catch this and clean up

The rest of this section is part of the full cheat sheet

Table 1: Process Listing with ps

Command	Example	Description
ps aux	`ps aux`	Lists all processes for all users with CPU%, MEM%, VSZ, RSS, and STAT columns (BSD style).
ps -ef	`ps -ef`	Lists all processes in full format including PPID (POSIX/UNIX style).
ps -eo (custom columns)	`ps -eo pid,ppid,ni,pcpu,pmem,comm`	• Prints only the user-specified columns • any keyword from `ps --help all` is valid
ps --sort	`ps -eo pid,pcpu,comm --sort=-%cpu`	• Sorts output by a field • prefix with `-` for descending order (e.g. top CPU consumers first).
ps -C (by command name)	`ps -C nginx -o pid=`	• Selects processes by exact executable name • suppresses header with `=`.
ps -p (by PID)	`ps -p 1234 -f`	Shows full info for a specific PID.
ps --ppid (children)	`ps --ppid 1234`	Lists all direct child processes of a given parent PID.
ps --forest	`ps -ef --forest`	Draws an ASCII tree of parent–child relationships.
ps -L (threads)	`ps -L -p 1234`	Adds an LWP (thread ID) column to show all threads inside a process.
ps -u / -U (by user)	`ps -u www-data`	Filters output to processes owned by a specific user (effective UID with `-u`, real UID with `-U`).

Table 2: Process State Codes (STAT Column)

Code	Example	Description
R (running)	`STAT: R`	Process is running or runnable — on the CPU or queued for it.

Table 3: Finding Processes with pgrep and pidof

Command	Example	Description
pgrep (basic)	`pgrep nginx`	Returns PIDs of all processes whose name matches the pattern.

Table 4: Linux Signals Reference

Signal	Example	Description
SIGTERM (15)	`kill 1234`	• Default signal from `kill` • requests graceful termination — process can catch this and clean up