macOS & Linux Basics
Key Takeaways
- macOS defaults to the APFS file system (since High Sierra, 2017), uses Time Machine for incremental backups, FileVault for full-disk encryption, Spotlight (Cmd+Space) for search, and zsh as its default shell.
- The Linux filesystem starts at root (/) with /home for users, /etc for configuration, /var for logs, /tmp for temporary files, /bin and /sbin for binaries, and /dev for device files.
- Core Linux commands include ls, cd, pwd, cp, mv, rm, chmod, chown, grep, find, sudo, df, top, ps, kill, and man; sudo elevates a single command to root.
- Linux octal permissions read owner-group-other with read=4, write=2, execute=1, so 755 = rwxr-xr-x and 644 = rw-r--r--; chmod sets them and chown changes ownership.
- Package managers differ by distribution family: apt (Debian/Ubuntu), dnf/yum (Red Hat/Fedora), pacman (Arch), and zypper (SUSE).
macOS Essentials
The exam tests macOS by analogy to Windows — know the Apple equivalent of each Windows feature.
| macOS feature | Role / Windows analog |
|---|---|
| Finder | File manager (= File Explorer) |
| Spotlight | Universal search, Cmd+Space |
| Time Machine | Automatic incremental backups to external/network disk |
| Mission Control | All open windows + virtual desktops (Spaces) |
| Keychain | Stored passwords and certificates |
| FileVault | Full-disk encryption (= BitLocker) |
| Terminal | CLI, default shell is zsh |
| AirDrop | Peer-to-peer file transfer between Apple devices |
| Gatekeeper | Blocks unsigned/unidentified app installs |
| System Settings | Config panel (= Control Panel) |
APFS (Apple File System) has been the default since macOS High Sierra (2017), adding native encryption, snapshots, space sharing, and crash protection; the older format was HFS+ (Mac OS Extended). Useful shortcuts: Cmd+Q quits an app, Cmd+W closes a window, and Cmd+Option+Esc opens Force Quit (the macOS analog of Ctrl+Alt+Del).
Linux Filesystem Hierarchy
Linux is a single tree rooted at / — there are no drive letters. Each top-level directory has a defined role.
| Path | Contents |
|---|---|
| / | Root of the entire tree |
| /home | User home directories (/home/username) |
| /root | The root user's home (not the same as /) |
| /etc | System-wide configuration files |
| /var | Variable data: logs in /var/log, mail, spool |
| /tmp | Temporary files, often cleared on reboot |
| /bin, /sbin | Essential user and system binaries |
| /usr | User programs and libraries |
| /dev | Device files (disks, terminals) |
| /proc | Virtual filesystem of process/kernel info |
| /mnt, /media | Manual and removable mount points |
Essential Linux Commands
| Command | Purpose | Example |
|---|---|---|
| ls / cd / pwd | List / change / print directory | ls -la |
| cp / mv / rm | Copy / move / remove | rm -rf dir/ |
| mkdir / touch | Make directory / empty file | mkdir proj |
| cat / less / nano / vi | View / edit text | cat /etc/hostname |
| grep / find | Search text / files | grep error /var/log/syslog |
| sudo / su | Elevate one command / switch user | sudo apt update |
| chmod / chown | Change permissions / ownership | chmod 755 run.sh |
| df / du | Disk space free / usage | df -h |
| top / ps / kill | Live processes / list / terminate | kill -9 1234 |
| ip addr / ping | Network config / connectivity | ip addr show |
| man | Manual pages | man chmod |
Linux File Permissions
Permissions display as -rwxrwxrwx: a type character followed by three triplets for owner, group, and other. Each triplet combines read (r=4), write (w=2), and execute (x=1).
| Octal | Symbolic | Meaning |
|---|---|---|
| 777 | rwxrwxrwx | Everyone full (insecure) |
| 755 | rwxr-xr-x | Owner full; others read+execute |
| 644 | rw-r--r-- | Owner read+write; others read |
| 700 | rwx------ | Owner only, full |
| 600 | rw------- | Owner only, read+write |
Worked example: chmod 640 report.txt gives the owner read+write (6), the group read (4), and everyone else nothing (0) — exactly rw-r-----. You can also use symbolic mode: chmod u+x app adds execute for the owner, chmod g-w file removes group write. chown alice:staff file reassigns owner to alice and group to staff.
Package Management
The right package tool depends on the distribution family — a common exam item.
| Family | Manager | Install command |
|---|---|---|
| Debian / Ubuntu | apt | sudo apt install pkg |
| Red Hat / Fedora / CentOS | dnf (yum) | sudo dnf install pkg |
| Arch | pacman | sudo pacman -S pkg |
| SUSE | zypper | sudo zypper install pkg |
Typical apt workflow: sudo apt update refreshes the package index, sudo apt upgrade updates installed packages, and sudo apt remove pkg uninstalls.
Cross-Platform Scenarios and Pitfalls
The exam tests macOS and Linux mostly as contrasts with Windows, so train yourself on the equivalences. When a ticket says a Mac user lost a file and wants yesterday's version, the answer is Time Machine, not System Restore. When a Mac will not install an app downloaded from the web and warns it is "from an unidentified developer," the gatekeeper of that behavior is literally Gatekeeper, adjusted under Privacy & Security — not antivirus and not a permissions error.
For full-disk encryption on a lost MacBook, the protective feature is FileVault, the direct analog of BitLocker, and like BitLocker it relies on a recovery key that must be stored safely.
Linux questions cluster around permissions and elevation. A user who runs a downloaded script and gets "Permission denied" most often lacks the execute bit; the fix is chmod +x script.sh (or chmod 755), not editing the file. A user who can read but not modify a system file in /etc needs sudo, because those files are owned by root and writable only by root. Remember that sudo elevates a single command while su switches into another user's full session — a scenario that wants one administrative action favors sudo for least privilege.
The numeric permission logic is worth drilling: to grant the owner full control and lock everyone else out entirely you compute 7-0-0 = 700; to let a web server's group read a config but keep it secret from others you use 640.
Package-manager mismatches are a classic distractor. A command that works on Ubuntu (apt install) will fail on a Red Hat or Fedora host, where the correct tool is dnf (or legacy yum); on Arch it is pacman -S. If a scenario shows apt failing with "command not found" on a CentOS server, the issue is the wrong package manager for the distribution, not a broken repository.
File-system gotcha: macOS uses APFS (or older HFS+) and Linux uses ext4, so an external drive formatted NTFS can be read on a Mac but generally not written without third-party drivers. The truly universal choice for moving large files among Windows, macOS, and Linux is exFAT, which every modern OS can read and write and which has no 4 GB file-size limit.
What is the macOS feature equivalent to Windows BitLocker for full-disk encryption?
In Linux, what access does the octal permission 755 grant?
Which Linux directory holds system-wide configuration files?
The Linux command that searches for a text pattern inside files is: _____
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