Week 5: Marketing's Macs and the warehouse Linux box

Installing and removing apps

macOS apps come in three file types:

• .dmg: a disk image; double-click to mount it, then drag the app into Applications
• .pkg: an installer package that runs the Installer wizard; used when files go in several places
• .app: the application bundle itself (really a folder that looks like one file)
• App Store: Apple-reviewed apps, installed and updated automatically

Exam tip Uninstalling: drag the .app to the Trash and empty it. Apps installed from a .pkg may need the vendor's uninstaller to remove all files.

System folders

Know where things live:

/Applications  apps for all users
/Users         home folders
               (/Users/rosa)
/Library       settings, fonts, support
               files shared by all users
/System        the OS itself, protected
~/Library      one user's prefs and
               caches (hidden); same as
               /Users/rosa/Library

Exam tip Resetting one user's app settings? Look in that user's ~/Library, not the system /Library.

System Preferences

System Preferences (renamed System Settings in macOS 13 Ventura) holds: Displays (resolution, arrangement), Networks (Wi-Fi, Ethernet, VPN), Printers & Scanners, Privacy (Privacy & Security: app access to camera, files, screen recording), Accessibility (VoiceOver, zoom) and Time Machine (backups).

Exam tip App can't record the screen in a video call? Privacy & Security > Screen Recording: allow the app.

macOS features

Know what each one does:

• Mission Control: shows all open windows and multiple desktops (Spaces)
• Keychain: stores passwords, certificates and keys (Keychain Access app)
• Spotlight: system-wide search, Cmd+Space
• iCloud: Apple's cloud; iCloud Drive syncs files; iMessage and FaceTime for messages and calls
• Gestures: multi-finger trackpad actions
• Finder: the file manager; Dock: the app bar
• Continuity: Mac and iPhone work together (Handoff, AirDrop, Universal Clipboard, calls)

Disk Utility, FileVault, Terminal, Force Quit

The admin tools:

• Disk Utility: First Aid repairs a disk; also erase, format (APFS, exFAT) and partition
• FileVault: full-disk encryption; keep the recovery key safe
• Terminal: the command line (zsh shell)
• Force Quit: Cmd+Option+Esc closes a frozen app (like End task)

Exam tip macOS's 'Task Manager' for a frozen app is Force Quit. Activity Monitor shows CPU and memory use.

File management commands

Linux is case-sensitive, and paths use forward slashes.

• ls: list files (ls -l details, ls -a hidden); pwd: print working directory
• mv: move or rename; cp: copy (cp -r for folders); rm: remove (rm -r for folders; no Recycle Bin!)
• chmod: change permissions (chmod 755 script.sh); chown: change owner (chown rosa:warehouse file)
• grep: search inside files for text (grep -i error /var/log/syslog)
• find: search for files by name, size or date (find /home -name '*.pdf')

Reading permissions

ls -l shows owner, group and permissions for owner/group/others.

$ ls -l lbl.sh
-rwxr-x--- 1 rosa warehouse 812 Oct 6 lbl.sh
  |  |  |
  |  |  +-- others: ---  no access
  |  +----- group:  r-x  read, execute
  +-------- owner:  rwx  read, write, run

r=4 w=2 x=1, so rwxr-x--- = 750
$ chmod 755 lbl.sh  (others get r-x)

Exam tip chmod changes WHAT can be done; chown changes WHO owns it.

Filesystem management

mount attaches a filesystem to a folder (mount /dev/sdb1 /mnt/usb); umount detaches it. fsck checks and repairs a Linux filesystem, like chkdsk. Run fsck on an unmounted filesystem.

Exam tip fsck on a mounted, in-use filesystem can corrupt it. Unmount first, or let it run at boot.

Administrative: su and sudo

The root account is the superuser (UID 0) and can do anything. su switches to another user (root by default) and needs THAT user's password. sudo runs one command as root using YOUR password, if /etc/sudoers allows it, and logs it.

Exam tip Best practice: don't sign in as root. Use sudo for single commands; it's logged and limited.

Package management

Linux installs software from repositories with a package manager:

Debian/Ubuntu:   sudo apt update
                 sudo apt install cups
                 sudo apt upgrade
Fedora/RHEL:     sudo dnf install cups
                 sudo dnf upgrade

Exam tip apt = Debian family. dnf = Red Hat family (replaced yum).