This chapter covers troubleshooting common macOS issues, a critical topic for the CompTIA A+ 220-1102 exam. You will learn to diagnose and resolve problems with booting, applications, storage, networking, and security on macOS systems. Expect around 5-7% of exam questions to touch on macOS troubleshooting, often in scenario-based multiple-choice questions. Mastery of these skills is essential for any IT support professional working with Apple devices.
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Think of a macOS system as a well-managed apartment building. The macOS kernel is the building manager, ensuring utilities (hardware drivers) work and enforcing rules (security policies). Applications are tenants, each with their own apartment (sandboxed environment). The Finder is the lobby directory, and System Preferences is the building's control panel. When a tenant (app) stops flushing their toilet (app hangs), the building manager (kernel) might force a flush (Force Quit). If the elevator (file system) gets stuck between floors (directory corruption), the building manager might need to run a diagnostic (First Aid in Disk Utility). Sometimes, a tenant's loud music (kernel panic) triggers the fire alarm (system crash). The building's main power switch (NVRAM) controls basic functions like door locks (display resolution) and intercom volume (sound output). Resetting the main power switch (resetting NVRAM) can resolve issues with these basics. The building's backup generator (Safe Boot) starts only essential systems (extensions and startup items) to isolate problems. If a tenant spills water (malware), the building manager quarantines the area (quarantine feature) and calls a cleanup crew (antimalware software). The building's security cameras (unified log) record every event, allowing the manager to review footage (log files) to diagnose issues. The building's maintenance log (Console app) helps track recurring problems. The building manager's master key (root password) can override all locks, but is rarely used to avoid security risks. Understanding this apartment building analogy helps you systematically troubleshoot macOS issues by identifying which system component is malfunctioning and applying the appropriate fix.
Overview of macOS Troubleshooting
macOS is a Unix-based operating system known for its stability and user-friendly interface. However, like any OS, it can encounter issues. Troubleshooting macOS requires understanding its unique architecture: the XNU kernel, the file system (APFS), the graphical interface (Aqua), and the system-wide logging system (unified log). Common problems include boot failures, application crashes, kernel panics, slow performance, network connectivity issues, and permission errors. The exam tests your ability to apply systematic troubleshooting methodologies and use built-in utilities to resolve these issues.
Boot Process and Startup Issues
The macOS boot process involves several stages: power-on self-test (POST), boot ROM, EFI boot, kernel loading, launchd initialization, and user login. Issues can arise at any stage. Common symptoms include: - No power: Check power source, cable, and battery. - Chime but no video: Could be display, GPU, or PRAM/NVRAM issue. - Spinning globe: Indicates network boot attempt (holding Option key) or missing boot volume. - Question mark folder: Means the system cannot find a valid System Folder. - Prohibitory sign (circle with slash): Indicates a corrupted system file or incompatible kernel extension. - Kernel panic: A screen with a message saying "You need to restart your computer" – usually caused by hardware, driver, or kernel extension issues.
Troubleshooting steps: - Reset NVRAM/PRAM: Non-Volatile Random-Access Memory stores settings like display resolution, startup disk, time zone, and sound volume. Resetting can resolve issues related to these settings. For Intel Macs, hold Command+Option+P+R during startup until the chime sounds twice. For Apple Silicon Macs, simply restart; NVRAM is automatically reset. - Reset SMC: System Management Controller manages power, battery, thermal, and other hardware functions. Symptoms of SMC issues include fan noise, battery not charging, keyboard backlight issues, and system not responding. Reset methods vary by Mac model: - Desktop Macs: Unplug power cord, wait 15 seconds, reconnect, wait 5 seconds, then turn on. - Laptops with non-removable battery: Shut down, plug in power, press Shift+Control+Option+Power button simultaneously for 10 seconds, then release and press Power. - Laptops with removable battery: Remove battery, hold power button for 5 seconds, reinsert battery, and start. - Safe Boot: Boot while holding the Shift key. This loads only essential kernel extensions and disables startup items and user login items. Use to isolate issues caused by third-party software or corrupted system caches. - Single-user mode: Boot with Command+S (Intel only) to get a command-line interface for file system repairs or manual troubleshooting. On Apple Silicon, use Recovery Mode. - Verbose mode: Boot with Command+V to see detailed logs during startup. Helps identify where the boot process fails. - Recovery Mode: Boot with Command+R (Intel) or hold the power button until you see "Loading startup options" (Apple Silicon). Provides utilities like Disk Utility, Terminal, and macOS Reinstall. Use to repair disk, restore from Time Machine, or reinstall macOS. - Target Disk Mode: Boot with T key to make the Mac act as an external hard drive, useful for data transfer when the OS won't boot.
Application and Process Issues
Applications can hang, crash, or become unresponsive. Common causes: insufficient memory, incompatible software, corrupted preferences, or permission issues.
Tools and techniques:
- Force Quit: Press Command+Option+Esc or choose Apple menu > Force Quit. Select the unresponsive app and click Force Quit.
- Activity Monitor: Located in /Applications/Utilities/. Shows CPU, memory, energy, disk, and network usage. Use to identify processes consuming excessive resources. You can force quit processes, inspect memory pressure, and check for "Not Responding" apps.
- Console app: View system logs, crash reports, and diagnostic messages. Use the search bar to filter by process name or keyword. Crash reports are stored in ~/Library/Logs/DiagnosticReports/.
- Terminal commands:
- top or htop (if installed): Real-time process monitoring.
- ps aux: List all running processes.
- kill -9 <PID>: Force kill a process by PID.
- lsof -i :<port>: List open network connections.
- Resetting application preferences: Delete or rename the .plist file in ~/Library/Preferences/ (e.g., com.apple.finder.plist). The app will recreate it with defaults. Use defaults delete command as an alternative.
- Reinstalling applications: Drag the app to Trash, then reinstall from a trusted source.
Common scenarios: - App won't open: Check if it's from an unidentified developer (Gatekeeper). Go to System Preferences > Security & Privacy > General, and click "Open Anyway". Alternatively, right-click the app and select Open. - App crashes on launch: Delete its preferences or check for corruption by reinstalling. - App is frozen: Use Force Quit; if that fails, use Activity Monitor to force quit.
Storage and File System Issues
macOS uses the Apple File System (APFS) by default, which is optimized for SSDs. Common issues include disk full, file system corruption, permissions problems, and Time Machine failures.
Tools and techniques:
- Disk Utility: Located in /Applications/Utilities/. Use First Aid to verify and repair disk and volume structures. First Aid checks the file system consistency and repairs corruption. For APFS, it can also fix snapshot issues. Run from Recovery Mode if the startup disk cannot be repaired while booted.
- Storage Management: Apple menu > About This Mac > Storage > Manage. Provides recommendations like emptying Trash, optimizing storage, and reducing clutter.
- Terminal commands:
- df -h: Display disk space usage.
- du -sh ~/Library: Show size of Library folder.
- diskutil list: List all disks and volumes.
- diskutil verifyVolume /: Verify the startup volume.
- diskutil repairVolume /: Repair the startup volume (usually requires Recovery Mode).
- Permissions repair: In older macOS versions (pre-El Capitan), Disk Utility had a Repair Disk Permissions option. In modern macOS, permissions are automatically maintained. However, you can manually reset home directory permissions using:
- sudo chown -R $(whoami) ~
- Or use the resetpassword command in Recovery Mode (not just for passwords, it also repairs home directory permissions).
- Time Machine: If backups fail, check the backup disk for errors using Disk Utility, ensure the disk is formatted as Mac OS Extended (Journaled) or APFS, and verify that Time Machine is not excluding the disk. Sometimes deleting old backups or starting a new backup set resolves issues.
Common scenarios:
- "Startup disk full": Free up space by emptying Trash, removing old files, using Storage Management, or deleting large files with du and find.
- "Disk not ejected properly": Usually indicates the disk was disconnected without unmounting. Use Disk Utility to repair, or force unmount with diskutil unmountDisk force /dev/diskX.
- File permissions errors: Even though macOS manages permissions, you can encounter issues when copying files from external drives or after restoring from backup. Use chmod and chown to correct.
Network Connectivity Issues
macOS network issues can be related to Wi-Fi, Ethernet, VPN, or network services. Common symptoms: no internet, slow speeds, intermittent disconnections, or inability to connect to specific services.
Tools and techniques:
- Network Utility: Located in /System/Library/CoreServices/Applications/ (or use Terminal commands). Provides ping, traceroute, lookup, and port scan.
- Wireless Diagnostics: Hold Option key and click Wi-Fi icon in menu bar > Open Wireless Diagnostics. This tool analyzes Wi-Fi environment, captures logs, and can assist with troubleshooting.
- Terminal commands:
- ping 8.8.8.8: Test basic connectivity.
- traceroute google.com: Trace route to host.
- nslookup google.com: DNS resolution.
- ifconfig: View network interfaces.
- networksetup -listallhardwareports: List all network interfaces.
- sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder: Flush DNS cache (macOS versions vary – use sudo killall -HUP mDNSResponder for modern versions).
- Renew DHCP lease: System Preferences > Network > Advanced > TCP/IP > Renew DHCP Lease.
- Delete Wi-Fi preferences: In rare cases, corrupted Wi-Fi configuration causes issues. Delete the file /Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist and restart.
- Check firewall: System Preferences > Security & Privacy > Firewall. Ensure it's not blocking necessary apps.
- VPN issues: Check connection logs in Console, verify credentials, and ensure the VPN type (L2TP, IPSec, IKEv2) is supported.
Common scenarios: - Wi-Fi connects but no internet: Check DNS settings, try pinging a known IP (8.8.8.8). If ping works, DNS is the issue. Flush DNS or set manual DNS (e.g., 8.8.8.8). - Ethernet not recognized: Check cable, try a different port, reset SMC, or check System Information (Apple menu > About This Mac > System Report > Network). - Slow Wi-Fi: Use Wireless Diagnostics to scan for interference, check channel congestion, or try changing router channel.
Security and Permission Issues
macOS has robust security features like Gatekeeper, FileVault, System Integrity Protection (SIP), and XProtect. Issues can arise from misconfigurations or legitimate software being blocked.
Tools and techniques:
- Gatekeeper: Controls which apps can be installed. Set in System Preferences > Security & Privacy > General. Options: App Store, App Store and identified developers, or Anywhere (hidden, enable via Terminal).
- System Integrity Protection (SIP): Protects system files from modification. Check status with csrutil status in Terminal. To disable/enable, boot into Recovery Mode and run csrutil disable or csrutil enable. Disabling SIP is rarely needed and reduces security.
- FileVault: Full-disk encryption. If you forget your password and don't have a recovery key, you may lose data. Use Recovery Mode to reset password if FileVault is off; if on, you need the recovery key or Apple ID.
- Malware: Use built-in XProtect and Malware Removal Tool (MRT). Third-party tools like Malwarebytes can help. Symptoms: pop-ups, redirects, slow performance. Check Activity Monitor for suspicious processes.
- Keychain issues: Keychain stores passwords. If it becomes corrupted, apps may ask for passwords repeatedly. Use Keychain Access (in /Applications/Utilities/) to repair or reset keychain.
- User account issues: Forgotten password, corrupted user account, or permission problems. Use Recovery Mode > Terminal > resetpassword to reset password or repair home directory.
Performance Issues
Slow performance can be due to insufficient RAM, high CPU usage, fragmented disk (less common with SSDs), or too many startup items.
Tools and techniques: - Activity Monitor: Check CPU, Memory, Energy, Disk, and Network tabs. High CPU usage from a single process may indicate a runaway process. Memory pressure graph shows how much memory is being used. - Startup items: System Preferences > Users & Groups > Login Items. Remove unnecessary items. - Optimize storage: Use Storage Management to offload files to iCloud, empty Trash automatically, and reduce clutter. - Reset SMC and NVRAM: As described, can resolve performance issues related to power management. - Reinstall macOS: As a last resort, backup data and reinstall macOS via Recovery Mode.
Printing Issues
Common problems: printer not recognized, print jobs stuck, or incorrect output.
Troubleshooting steps:
Check physical connections (USB, network).
System Preferences > Printers & Scanners: Remove and re-add printer.
Reset printing system: Right-click in the printer list and select "Reset printing system". This removes all printers and resets settings.
Check printer queue: Open printer, delete stuck jobs, and restart printer.
Verify drivers: Download latest drivers from manufacturer.
Use Printer Utility: Some printers have diagnostic tools.
System Updates and Recovery
macOS updates can fail or cause issues. Use Software Update in System Preferences. If an update fails, try:
Restart and try again.
Download the update manually from Apple Support.
Boot into Recovery Mode and reinstall macOS (keeps your data).
Use Terminal commands like softwareupdate --list and softwareupdate --install -a.
Conclusion
Troubleshooting macOS requires a methodical approach: identify symptoms, isolate the cause, and apply the appropriate fix. Use built-in utilities like Disk Utility, Activity Monitor, Console, and Terminal. Understand the boot process, file system, and security features. The exam will test your ability to choose the correct tool or step for a given scenario. Practice these skills in a lab environment or on a real Mac to build confidence.
Identify the Symptom
The first step is to clearly identify and describe the problem. Ask the user: What exactly is happening? When did it start? Did anything change recently (software install, update, new hardware)? Is it reproducible? Document the symptoms: error messages, behavior (e.g., app crashes, slow performance, no boot). This step narrows down the possible causes. For example, a "spinning beachball" indicates an unresponsive app, while a kernel panic suggests a deeper system issue. Use built-in logging tools like Console to capture error messages. On the exam, you'll be given a scenario; read carefully to identify the key symptom.
Isolate the Problem Scope
Determine if the issue affects one user, multiple users, or the entire system. Test with a different user account (create a guest account) to see if the problem persists. If it's user-specific, the issue is likely in that user's preferences or Library folder. If it affects all users, it's system-wide, possibly a hardware or OS-level problem. Also, check if the issue occurs in Safe Boot mode. Booting while holding Shift loads only essential kernel extensions and disables startup items. If the problem disappears in Safe Boot, it's likely caused by a third-party kernel extension or startup item. This isolation technique is critical for efficient troubleshooting.
Check Basic Hardware and Connections
Before diving into software, rule out simple hardware problems. For boot issues, ensure power cable is connected, battery is charged, and peripherals are disconnected (especially USB devices that can cause conflicts). For network issues, check cables, Wi-Fi is on, and router is working. For display issues, check brightness, external monitor connection, and try resetting NVRAM. For audio issues, check volume, mute, and output device selection. Use System Information (Apple menu > About This Mac > System Report) to verify hardware is detected. For example, if USB ports aren't working, check System Report > USB to see if the device is recognized. This step often resolves simple issues quickly.
Use Built-in Diagnostic Tools
macOS provides several utilities for troubleshooting. For disk issues, use Disk Utility > First Aid to verify and repair the file system. For performance issues, use Activity Monitor to identify resource hogs. For network issues, use Network Utility (or Terminal commands like ping, traceroute) and Wireless Diagnostics. For application crashes, use Console to view crash logs. For system-wide issues, use Terminal commands like `top`, `ps`, `dmesg` (for kernel messages), and `sysdiagnose` (to generate a comprehensive diagnostic report). `sysdiagnose` collects logs, system configuration, and performance data; run with `sudo sysdiagnose` and share with Apple Support if needed. These tools provide detailed information to pinpoint the root cause.
Apply Targeted Fixes
Based on the diagnosis, apply the appropriate fix. Common fixes include: resetting NVRAM/SMC, booting into Safe Mode, repairing disk permissions (if applicable), deleting preference files, reinstalling applications, flushing DNS cache, renewing DHCP lease, or updating macOS. For kernel panics, check for incompatible kernel extensions (kexts) in /Library/Extensions/ or /System/Library/Extensions/. Remove third-party kexts or disable them by booting with `keepsyms=1` and checking the panic log. For malware, run Malwarebytes or use the built-in XProtect. For forgotten passwords, use Recovery Mode > Terminal > `resetpassword`. Always back up data before major operations like reinstalling macOS. Apply one fix at a time and test after each change to identify the solution.
Verify Resolution and Document
After applying a fix, verify that the issue is resolved. Test thoroughly: restart the system, perform the action that previously caused the problem, and check that no new issues have appeared. For example, if you fixed a Wi-Fi issue, test internet access, internal network resources, and VPN connectivity. If the problem persists, re-evaluate your diagnosis and try alternative fixes. Once resolved, document the problem, steps taken, and solution. This documentation helps with future troubleshooting and can be shared with colleagues. On the exam, you may be asked to determine the most likely cause or the next step; good documentation habits reinforce the troubleshooting methodology.
In an enterprise environment with hundreds of macOS devices, troubleshooting becomes systematic and often automated. For example, a large design firm uses Macs for graphic design. A common issue is Photoshop crashing on startup. The IT team uses a script that runs sysdiagnose and collects crash logs from Console. They find that the crash is caused by a corrupt preference file in ~/Library/Preferences/com.adobe.Photoshop.plist. They deploy a script via Jamf Pro (MDM) to delete the plist file and restart Photoshop. This resolves the issue for all users without manual intervention. Another scenario: a school with Mac labs experiences kernel panics after a macOS update. The IT team identifies that the panic is caused by an outdated third-party kernel extension for a specific peripheral. They use Safe Boot to confirm, then update the driver or remove the kext using kextunload. They also disable SIP temporarily to remove the kext if needed. For network issues in a corporate office, users report intermittent Wi-Fi drops. The network team uses Wireless Diagnostics and finds high interference on channel 6. They change the access point channel to 11 and enable 5 GHz band preference. They also configure macOS to forget and reconnect to the network using a configuration profile. In another case, a user's Mac won't boot past the Apple logo. The support team uses Target Disk Mode to connect the Mac to another Mac and runs Disk Utility First Aid on the startup volume, which repairs the file system. If that fails, they use Time Machine to restore from a backup. These real-world examples highlight the importance of systematic troubleshooting and leveraging macOS built-in tools and remote management capabilities.
The CompTIA A+ 220-1102 exam tests macOS troubleshooting under Objective 3.1: Given a scenario, troubleshoot common problems on macOS. Key areas: boot issues (kernel panic, spinning globe, prohibited sign), application issues (force quit, Activity Monitor), storage issues (Disk Utility, First Aid), network issues (Wireless Diagnostics, Network Utility), and security issues (Gatekeeper, FileVault). Common wrong answers: choosing "Repair Disk Permissions" for modern macOS (this option no longer exists in Disk Utility for APFS; use First Aid instead). Another trap: selecting "Reset PRAM" when the problem is a kernel panic caused by a kext; the correct step is to boot in Safe Mode or remove the kext. Candidates also confuse SMC reset with NVRAM reset: SMC handles power/hardware, NVRAM handles settings. For network issues, candidates may choose "Renew DHCP lease" when the problem is DNS; the correct step is to flush DNS cache. For application crashes, candidates often select "Reinstall macOS" too early; the correct first step is to check Console logs or reset preferences. The exam loves specific values: Safe Boot uses the Shift key; Recovery Mode uses Command+R (Intel) or hold power button (Apple Silicon); NVRAM reset uses Command+Option+P+R; SMC reset varies by model. Know the exact key combinations. Edge cases: FileVault encrypted drives require recovery key or Apple ID to reset password; Target Disk Mode requires a Thunderbolt or FireWire cable; older Macs may have different SMC reset procedures. To eliminate wrong answers, ask: Does the tool exist? Is it appropriate for the symptom? For example, if the symptom is "app won't open because it's from an unidentified developer," the answer is Gatekeeper settings, not reinstalling macOS.
macOS boot issues: use Safe Boot (Shift), Recovery Mode (Command+R), NVRAM reset (Command+Option+P+R), SMC reset (varies by model).
Application issues: Force Quit (Command+Option+Esc), Activity Monitor, Console for crash logs, reset preferences by deleting .plist files.
Storage issues: Disk Utility First Aid for file system repairs, Storage Management for space optimization, Terminal commands like df, du, diskutil.
Network issues: ping, traceroute, nslookup, Wireless Diagnostics, flush DNS with `sudo killall -HUP mDNSResponder`, renew DHCP lease.
Security issues: Gatekeeper settings for app installation, FileVault for encryption, SIP protection for system files, Keychain Access for password issues.
Performance issues: Activity Monitor for resource usage, manage login items, reset SMC/NVRAM, reinstall macOS as last resort.
Always back up before major operations. Use Time Machine or other backup solutions.
The exam tests key combinations and tool names: know Safe Boot, Recovery Mode, Target Disk Mode, and their respective key commands.
These come up on the exam all the time. Here's how to tell them apart.
NVRAM Reset
Resets display, sound, startup disk, and time zone settings.
Performed by holding Command+Option+P+R during boot (Intel).
Does not affect power management or hardware functions.
Can resolve issues like wrong resolution or startup disk selection.
On Apple Silicon, NVRAM is automatically reset on restart.
SMC Reset
Resets power management, battery, thermal, and other hardware functions.
Reset procedure varies by Mac model (desktop, laptop with/without removable battery).
Can resolve issues like fan noise, battery not charging, keyboard backlight issues.
Does not affect display or sound settings.
Apple Silicon Macs do not have an SMC; power management is handled differently.
Mistake
Resetting NVRAM will fix all boot problems.
Correct
NVRAM reset only affects settings like display resolution, startup disk, and sound volume. It does not fix kernel panics caused by hardware or kexts. For those, Safe Boot or removing kexts is needed.
Mistake
Repair Disk Permissions in Disk Utility fixes modern macOS issues.
Correct
Repair Disk Permissions was removed in OS X El Capitan. For APFS volumes, use First Aid which checks and repairs the file system structure, not individual file permissions. Permissions are automatically managed.
Mistake
Force Quit is the only way to close a frozen app.
Correct
You can also use Activity Monitor to force quit a process, or use Terminal commands like `kill -9 <PID>`. Force Quit is the GUI method, but Activity Monitor provides more details.
Mistake
Safe Mode disables all third-party software.
Correct
Safe Mode disables startup items, login items, and loads only essential kernel extensions. However, some third-party software that is installed as a kernel extension may still load if it is signed and essential. Safe Mode primarily isolates issues caused by non-essential software.
Mistake
macOS doesn't get malware.
Correct
macOS can get malware, though less frequently than Windows. Built-in protections like XProtect and MRT help, but users can still be infected via social engineering. Use Activity Monitor to check for suspicious processes and run antimalware tools if needed.
Reveal each answer, then mark whether you got it right. Score 60%+ to unlock the next chapter.
First, try booting in Safe Mode (hold Shift during startup). If that works, the issue is likely a third-party kernel extension or startup item. If not, boot into Recovery Mode (Command+R) and run Disk Utility > First Aid on the startup disk. If First Aid reports errors, attempt to repair. If the disk is fine, try reinstalling macOS (keeps your data). If still not booting, you may need to restore from Time Machine or use Target Disk Mode to transfer data.
NVRAM (Non-Volatile RAM) stores settings like display resolution, startup disk, and sound volume. Resetting it can fix issues related to these settings. SMC (System Management Controller) manages power, battery, thermal, and other hardware functions. Resetting SMC can fix issues like fan noise, battery not charging, or system not responding. NVRAM reset is done with Command+Option+P+R; SMC reset varies by Mac model.
Press Command+Option+Esc to open the Force Quit Applications window. Select the unresponsive app and click Force Quit. Alternatively, use Activity Monitor (in /Applications/Utilities/), select the process, and click the X button. You can also use Terminal: type `killall [app name]` or `kill -9 [PID]`.
If FileVault is off, boot into Recovery Mode (Command+R), go to Terminal, and type `resetpassword`. Follow the prompts to reset the password. If FileVault is on, you need the recovery key or use your Apple ID if it's set as the password reset option. You can also use another admin account to reset the password via System Preferences > Users & Groups.
First, ensure Wi-Fi is on and you're connected to the correct network. Try renewing DHCP lease: System Preferences > Network > Advanced > TCP/IP > Renew DHCP Lease. Flush DNS cache: `sudo killall -HUP mDNSResponder`. If still issues, use Wireless Diagnostics (hold Option and click Wi-Fi icon > Open Wireless Diagnostics) to analyze the environment. Check for interference, change router channel, or forget the network and reconnect.
This indicates a corrupted system file or incompatible kernel extension. Boot into Recovery Mode (Command+R) and run Disk Utility > First Aid. If that doesn't fix it, try reinstalling macOS. If you recently installed a kernel extension, boot in Safe Mode (Shift) and remove it. You can also use Target Disk Mode to transfer data before reinstalling.
Open Activity Monitor and look for processes with high CPU usage or suspicious names. Check Console for unusual log entries. Use built-in XProtect and Malware Removal Tool (MRT) which run automatically. For a thorough scan, use third-party tools like Malwarebytes. Symptoms include pop-ups, redirects, and slow performance.
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