LICM: Finding Your Way on a Linux System

Domain 2 - Finding Your Way on a Linux System

This domain tests command-line literacy: navigating the filesystem, getting help without the internet, and creating or editing files at the shell. It rewards knowing exact syntax and the difference between absolute and relative paths.

Core rules

• The shell expands ~ to your home directory, . to the current directory and .. to the parent. Absolute paths start at /; relative paths start from $PWD.
• Commands are found by searching $PATH left to right. echo $PATH shows it; export PATH=$PATH:/opt/bin appends a directory for the current shell and its children.
• Help sources, in order of specificity: command --help, man command, info command, and /usr/share/doc/<package>/.
• man sections: 1 user commands, 2 system calls, 3 library functions, 5 file formats (e.g. man 5 passwd), 8 admin commands. man -k keyword (same as apropos) searches descriptions.
• ls -l shows type, permissions, links, owner, group, size, date and name; ls -a includes dotfiles.
• cp -r copies directories, mv renames or moves, rm -r removes recursively, mkdir -p creates intermediate directories, and file guesses content type from magic bytes, not from the extension.

Worked example

You are in /home/anna and need the format of the password file. man passwd returns the command in section 1; man 5 passwd returns the file format, which is the correct answer. Reasoning: the same name lives in several sections, and the section number disambiguates them.

Traps

• rm has no recycle bin and no undo.
• cd .. from / stays at /.
• Aliases and shell functions can shadow a binary; type tells you which one runs.
• mkdir a/b fails if a is missing - use -p.