Core Linux Commands#

`man`#

Display manual pages for commands:

man ls

Comprehensive reference (syntax, options, behaviour)
Organized into sections (e.g., user commands, system calls)

`apropos`#

Search manual page descriptions by keyword:

apropos network

Useful when you don’t know the exact command name

External Resource#

explainshell — explains command syntax interactively

Common System Commands#

Command	Description
`whoami`	Print current user
`id`	Show user and group IDs
`hostname`	Get/set system hostname
`uname`	System/kernel information
`pwd`	Print current directory
`env`	Show or set environment variables

Networking#

Command	Description
`ifconfig`	Configure/view network interfaces (legacy)
`ip`	Modern network configuration tool
`netstat`	Network status (legacy)
`ss`	Socket inspection (modern replacement for netstat)

Process & System Inspection#

Command	Description
`ps`	Process status
`who`	Logged-in users
`lsof`	Open files by processes

Hardware Inspection#

Command	Description
`lsblk`	Block devices (disks)
`lsusb`	USB devices
`lspci`	PCI devices

File & Path Utilities#

`ls`#

List directory contents:

ls -l /etc

`which`#

Locate executable in $PATH:

which python

Returns the path of the command being executed

File Search#

`find`#

Search filesystem with filters and actions.

Example#

find / -type f -name "*.conf" -user root -size +20k -newermt 2020-03-03 -exec ls -al {} \; 2>/dev/null

Key Options#

Option	Description
`-type f`	Search for files (`d` for directories)
`-name "*.conf"`	Match filename pattern
`-user root`	Filter by owner
`-size +20k`	Files larger than 20 KiB
`-newermt DATE`	Modified after date
`-exec ... {}`	Execute command per result
`2>/dev/null`	Suppress errors (not a `find` option)

Notes#

{} is replaced with each match
\; terminates -exec (escaped to avoid shell interpretation)

`locate`#

Fast file search using indexed database:

locate "*.conf"

Update Database#

sudo updatedb

Characteristics#

Feature	`find`	`locate`
Search Method	Real-time scan	Prebuilt index
Speed	Slower	Very fast
Accuracy	Always current	May be stale
Filtering	Advanced	Limited

Mental Model#

Use man / apropos for discovery
Use which to resolve execution path
Use find for precise, real-time queries
Use locate for fast, broad searches