Linux and macOS

Lesson 13 · Linux and macOS · Download .docx

Objectives

Use fundamental Linux commands for file management and system administration
Explain Linux file permissions and the chmod notation
Compare macOS system tools to their Windows equivalents

Key terms

ls -la: Lists all files including hidden with permissions, owner, size, and date.
chmod: Linux command changing file/directory permissions using octal or symbolic notation.
sudo: Runs a command with superuser (root) privileges as defined in /etc/sudoers.
apt: Advanced Package Tool — Debian/Ubuntu package manager for installing software.
dnf: Package manager for Fedora and RHEL-based Linux distributions.
grep: Searches file contents for text patterns; supports regular expressions.
top: Interactive real-time process viewer showing CPU and memory usage per process.
zsh: Z shell — default shell in macOS since Catalina (2019); replaced bash.
APFS: Apple File System — macOS default since High Sierra (2017); optimized for SSDs.
Homebrew: Third-party macOS package manager — equivalent to apt on Ubuntu.
/ (root): Linux file system root — all drives and directories mount under this single point.
rwxr-xr-x: chmod 755 permission — owner can read/write/execute; group and others can read/execute.

The concept

LINUX FILE SYSTEM AND COMMANDS

Linux uses a single file system tree rooted at / (forward slash). Unlike Windows, which assigns drive letters (C:, D:), Linux mounts all storage — including external drives and network shares — as subdirectories under /. Home directories are at /home/username; configuration files are in /etc; binaries in /usr/bin.

Critical commands: 'ls' lists directory contents; add '-l' for long format (permissions + metadata) and '-a' for hidden files. 'cd' changes directory; 'pwd' prints the current path. 'grep pattern file' searches a file's contents for matching lines.

FILE PERMISSIONS

Linux permissions are shown as rwxrwxrwx — three groups of three characters for owner, group, and others. r=read (4), w=write (2), x=execute (1). Octal notation combines these: chmod 755 = owner rwx (7), group r-x (5), others r-x (5). chmod 644 = owner rw- (6), group r-- (4), others r-- (4) — standard for text files.

PACKAGE MANAGERS

Different Linux distributions use different package managers: Ubuntu/Debian use 'apt'; Fedora/RHEL use 'dnf'; Arch uses 'pacman'. On macOS, Homebrew ('brew install') fills the same role — installing command-line tools and GUI apps from a curated repository.

macOS SPECIFICS

The default macOS shell changed from bash to zsh with Catalina (2019). macOS uses APFS (Apple File System) as its default filesystem — optimized for SSDs with snapshot support and space sharing. The equivalent of Windows Task Manager is Activity Monitor; the equivalent of regedit is the Defaults system or property list (.plist) files. Homebrew is the de facto package manager for developer tools.

Worked examples

Example 1: A new Ubuntu server needs Node.js installed. Commands: 'sudo apt update' (refresh package list), then 'sudo apt install nodejs npm'. Verify with 'node --version'. On Fedora: 'sudo dnf install nodejs'. The package manager handles dependency resolution automatically.

Example 2: A file named deploy.sh needs to be executable by the owner but readable only by group and others. Correct permission: chmod 744 (owner: rwx=7, group: r--=4, others: r--=4). Verify with 'ls -la deploy.sh' which should show '-rwxr--r--'.

Common mistakes

Using 'ls' instead of 'ls -la' — missing hidden files and permission details needed for troubleshooting.
Confusing chmod 755 (rwxr-xr-x) with chmod 777 (rwxrwxrwx) — 777 grants everyone write access, a security risk.
Running commands as root instead of using sudo — permanently running as root bypasses the safety of per-command elevation.
Confusing 'su' (switch user) with 'sudo' — sudo runs one command elevated; 'su -' switches the full session.
Attempting to use 'apt' on Fedora/RHEL or 'dnf' on Ubuntu — package managers are distribution-specific.

Self-check

Try each one before you look. A miss here costs nothing and tells you exactly what to reread.

1. 'ls -la' shows:

2. chmod 755 sets permissions to:

3. Which command installs a package on Ubuntu?

4. macOS Terminal uses which default shell?

5. The Linux file system root is mounted at:

Canvas is the official record. This companion enhances the PGCC curriculum; it does not replace it. Last name and class year only. Students with a 504 plan or IEP: your accommodations apply.

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