Reset macOS & Prepare for Development (Complete Guide 2)

Overview of Changes in macOS 15 “Sequoia”

• Recovery Mode Entry (Sequoia):

  • On Apple Silicon (M1/M2/M3), you hold down the Power button until “Loading Startup Options” appears, then select Options → Continue to enter Recovery Mode (iBoysoft).
  • On Intel-based Macs, you still restart and hold ⌘ Command + R until the Apple logo appears to enter Recovery Mode (Apple Support).

• Default Shell: zsh:

  • Since macOS Catalina (10.15), Apple replaced Bash with zsh as the default login and interactive shell (Ask Different, Wikipedia). Sequoia continues using zsh by default.

• Checklists:

  • At the end of each major section, you’ll find a Markdown checkbox (- [ ] …) so you can mark tasks complete as you go.

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1. Backup Your Data (Mandatory!)

1. Connect an External Drive: Ensure it’s at least as large as your Mac’s internal storage.
2. Open Time Machine: Go to Apple menu → System Settings → General → Time Machine (Apple Support).
3. Select Backup Disk: Click “Add Backup Disk…” and choose your external drive.
4. Wait for Backup to Finish: Don’t proceed until Time Machine’s initial backup completes.

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2. Reset macOS 15 (Erase & Reinstall)

2.1 Enter Recovery Mode

• Apple Silicon (M1/M2/M3):

  1. Shut down your Mac.
  2. Press and hold the Power button until you see “Loading Startup Options.”
  3. Select Options, then click Continue to load the Recovery environment (iBoysoft).

• Intel-Based Macs:

  1. Shut down or restart your Mac.
  2. Immediately hold ⌘ Command + R until the Apple logo appears.
  3. Release the keys when you see the macOS Recovery utilities window (Apple Support, iBoysoft).

2.2 Erase Your Disk

1. In the Recovery app window, select Disk Utility and click Continue (Apple Support).

2. In Disk Utility’s sidebar, choose Macintosh HD (or whatever you named your startup volume).

3. Click Erase (or Erase Volume Group if shown) (Apple Support).

4. Set:

   • Name: Macintosh HD
   • Format: APFS
   • Scheme: GUID Partition Map (on Intel) or simply APFS on Apple Silicon (Apple Support).

5. Confirm by clicking Erase (or Erase Volume Group).

2.3 Reinstall macOS Sequoia

1. After erasing, quit Disk Utility to return to the Recovery utilities.
2. Select Reinstall macOS Sequoia (it may display as “Reinstall macOS”) and click Continue (Apple Support, iBoysoft).
3. Follow the on-screen prompts—macOS will download a fresh copy of Sequoia and install (this can take 20–60 minutes depending on your connection).

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3. Fast Setup (Skip Unnecessary Steps)

Immediately after installation, you’ll see Sequoia’s Setup Assistant. To minimize distractions:

1. Country/Region: Select yours and click Continue.
2. Wi-Fi: Connect to your network (required for signing in and software updates).
3. Data Migration: Choose “Not Now” if you want a clean slate.
4. Apple ID: Click “Set Up Later” → Skip.
5. Create Admin Account: Provide your name, account name, and password. Uncheck Touch ID until after initial configuration.
6. Location Services: Deselect or click “Don’t Use”.
7. Analytics & Usage: Uncheck both “Share Analytics” and “Share With App Developers.”
8. Siri: Choose “Set Up Later” → Continue.

After that, you should see your new desktop—no extra accounts or old files.

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4. Terminal Quickstart & zsh Configuration

4.1 Launch Terminal

• Press ⌘ Command + Space, type Terminal, and press Enter. Since Sequoia uses zsh by default, you’ll be dropped into a zsh prompt (%). (Ask Different, Wikipedia).

4.2 Basic zsh Customization

1. Create ~/.zshrc (if it doesn’t exist):

   touch ~/.zshrc
   

2. Open ~/.zshrc in a text editor (e.g., nano ~/.zshrc).

3. Add Common Aliases & PATH Adjustments:

   # Set up Homebrew in PATH for Apple Silicon; adjust if on Intel
   if [[ -d /opt/homebrew/bin ]]; then
     export PATH="/opt/homebrew/bin:$PATH"
   else
     export PATH="/usr/local/bin:$PATH"
   fi
   
   # Prompt customization (optional)
   autoload -Uz promptinit
   promptinit
   prompt adam1
   
   # Example aliases
   alias ll='ls -lah'
   alias code='open -a "Visual Studio Code"'
   

4. Save & Exit (Ctrl + O, Enter, then Ctrl + X in nano).

5. Apply Changes:

   source ~/.zshrc
   

   You should now see your new prompt theme and have aliases available (Wikipedia).

4.3 Suppressing Bash Deprecation Warnings (Optional)

If you ever invoke Bash (e.g., via bash), you’ll see a message reminding you that zsh is now default. To silence that message when running Bash interactively:

echo 'export BASH_SILENCE_DEPRECATION_WARNING=1' >> ~/.zshrc
source ~/.zshrc

This sets the environment variable so that invoking Bash won’t repeatedly show the “default shell is now zsh” warning (Ask Different).

4.4 Quick Launch Common Apps (Example zsh Function)

Add a helper function to ~/.zshrc to open frequently used apps in one command:

function quickstart() {
  open -a Safari
  open -a Notes
  open -a "Activity Monitor"
}

After saving and source ~/.zshrc, run:

quickstart

This opens Safari, Notes, and Activity Monitor simultaneously .

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5. Development Environment Setup

5.1 Install Homebrew & Core Tools (zsh-Friendly)

In zsh, paste the following to install Homebrew and essential CLI tools:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

# After Homebrew is installed, ensure its path is loaded
if [[ -d /opt/homebrew/bin ]]; then
  echo 'eval "$(/opt/homebrew/bin/brew shellenv)"' >> ~/.zshrc
  eval "$(/opt/homebrew/bin/brew shellenv)"
elif [[ -d /usr/local/bin ]]; then
  echo 'eval "$(/usr/local/bin/brew shellenv)"' >> ~/.zshrc
  eval "$(/usr/local/bin/brew shellenv)"
fi

# Install essential command-line tools
brew install git python node

• Git: for version control.
• Python: scripting and automation.
• Node.js: JavaScript runtime.

Note: On Apple Silicon, Brew installs into /opt/homebrew/bin; on Intel, it’s usually /usr/local/bin (Wikipedia, Microsoft Learn).

5.2 Install GUI Applications

From the same zsh prompt, run:

brew install --cask warp
brew install --cask miniconda
brew install --cask google-chrome

• Warp: modern terminal alternative.
• Miniconda: Python environment manager.
• Google Chrome: web browser.

5.3 Git Configuration

In zsh, set your Git identity:

git config --global user.name "Your Name"
git config --global user.email "[e-mail]"

Verify by running git config --list (Wikipedia).

5.4 Create Development Folders

mkdir -p ~/Developer/{projects,scripts,backups}

This yields:

• ~/Developer/projects
• ~/Developer/scripts
• ~/Developer/backups

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6. Post-Install Pro Tips

1. Enable Firewall:

   • Go to System Settings → Network → Firewall (Sequoia moves some settings around; search “Firewall” if you don’t see it immediately).
   • Turn Firewall on and configure “Block all incoming connections” as desired (Apple Support, iBoysoft).

2. Install Xcode Command-Line Tools:

   xcode-select --install
   

   This is required for compilers and certain Homebrew packages (Wikipedia, iBoysoft).

3. Configure Time Machine for Regular Backups:

   • Return to System Settings → General → Time Machine.
   • Enable “Back Up Automatically” and choose your backup disk.

4. Keyboard Shortcuts:

   • ⌘ Command + Space: Spotlight.
   • ⌘ Command + Tab: App switcher.
   • ⌃ Control + ⌘ Command + Q: Lock screen immediately (Apple Support, iBoysoft).

5. Check for System Updates:

   • Go to System Settings → General → Software Update.
   • Always keep Sequoia patched (it’s a ~12 GB download initially, plus ~4 GB for CLI tools over time).

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7. Final Checklist & Estimated Timeline

• Total time to complete this process: approximately 60–90 minutes (this includes downloading Sequoia, installing tools, and configuring zsh).

Below is the final summary checklist. Mark each item as you go:

Final Checklist:

Once all boxes are checked, you’ll have a fresh, zsh-powered, Sequoia-ready development environment! 🚀

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References

1. Erase & Reinstall macOS: Apple Support “Erase and reinstall macOS” (Apple Support)
2. Clean Install Sequoia: iBoysoft “How to clean install macOS Sequoia” (iBoysoft)
3. zsh Default Shell: Apple Support kb “HT208050” & Wikipedia “Z shell” (Ask Different, Wikipedia)
4. Recovery Mode (Intel vs Apple Silicon): iBoysoft & Donemax “Two Methods to Reinstall macOS Sequoia” (iBoysoft, Donemax, Apple Support)
5. PowerShell on macOS 15 (confirms Sequoia support): Microsoft Documentation (Microsoft Learn)
6. Suppressing Zsh Warnings: StackOverflow “Suppressing the default interactive shell is now zsh” (Ask Different)
7. Proper Homebrew Path for zsh: Wikipedia “Z shell” & AlvinWanJala Blog “Switch from zsh to bash” (Wikipedia, alvinwanjala.com)

If you have questions about any of these steps—especially around Recovery Mode or zsh configuration—feel free to ask!