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Problems and fixes

The symptom, the cause, and a step-by-step fix. Commands inside the steps copy in one click.

// In short

16 write-ups of common macOS problems: symptoms, cause, and numbered fix steps. Commands inside the steps copy in one click, and every write-up links to related commands and apps from this section.

Your Mac
Homebrew in /opt/homebrew

kernel_task eating 300–500% CPU

gets in the way
Symptoms

Fans are roaring, the Mac lags, and Activity Monitor shows kernel_task consuming most of the CPU.

What to do

  1. Don't panic: kernel_task isn't a virus but a protection mechanism. It "occupies" the CPU to stop other processes from overheating the Mac.

  2. Find the real heat source — usually a third-party process or a browser tab:

    ps aux | sort -nrk 3 | head -10

  3. Quit the offending process. Check the vents aren't blocked and the MacBook isn't sitting on a blanket.

  4. Disconnect peripherals one by one (external monitors and cheap USB-C hubs especially) — they're a common heat source.

  5. If nothing helps — restart. A persistent issue on the same hardware warrants an SMC reset (Intel) or a service visit.

Commands used hereTop 10 processes by CPU usageUptime and system load

mds_stores hogging disk and CPU

not urgent
Symptoms

After a macOS update or plugging in an external drive, the mds_stores process loads the CPU and disk for a long time.

What to do

  1. That's the Spotlight indexer. After major disk changes it legitimately needs time — from 20 minutes to a couple of hours.

  2. If the load doesn't drop after several hours, restart the indexing service:

    sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist && sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist

  3. Still no luck — fully reindex the disk (indexing restarts from scratch):

    sudo mdutil -E /

  4. Exclude heavy working folders (node_modules, backups, VMs) from indexing: Settings → Spotlight → Search Privacy.

Commands used hereRestart the Spotlight serviceFull Spotlight reindexTop 10 processes by CPU usage

"App is damaged and can't be opened"

gets in the way
Symptoms

macOS refuses to launch a downloaded app, offering to move it to the Trash.

What to do

  1. Make sure the app came from the developer's official site, not a "free software collection".

  2. Try the legitimate path first: right-click the app → Open → confirm in the dialog.

  3. Check that Gatekeeper is enabled at all:

    spctl --status

  4. If you trust the source, strip the quarantine flag manually (replace the path):

    xattr -d com.apple.quarantine /Applications/AppName.app

  5. Message came back — the file really is corrupted. Download again or install via Homebrew: brew install --cask <name>.

Commands used hereGatekeeper statusRemove app quarantine
Might helpHomebrew

No sound or crackling audio

not urgent
Symptoms

The volume control doesn't respond, sound is gone entirely, or you hear clicks and crackling.

What to do

  1. Check the obvious: Settings → Sound → Output — is the right device selected (not "external monitor")?

  2. Restart the audio daemon — fixes 9 out of 10 cases:

    sudo killall coreaudiod

  3. Open "Audio MIDI Setup" and check the output sample rate: a 44.1/48 kHz mismatch causes crackling. Set it back to 44100 Hz.

  4. Check the output isn't muted programmatically:

    osascript -e "set volume output volume 50"

  5. Crackling in one app only — the problem is that app, not the system. Update or reinstall it.

Commands used hereReset the CoreAudio serviceSet the volume from Terminal

Wi-Fi dropping or "connected, no internet"

gets in the way
Symptoms

The connection drops regularly, or the Wi-Fi icon is active but sites won't open.

What to do

  1. Forget the network (Settings → Wi-Fi → Details → Forget) and reconnect with the password.

  2. Flush the DNS cache — a common cause of "everything connected, nothing works":

    sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

  3. Request a fresh IP address from the router:

    sudo ipconfig set en0 DHCP

  4. Fully restart the wireless module (the connection drops for a couple of seconds):

    sudo ifconfig en0 down && sudo ifconfig en0 up

  5. If you have both bands at home — try the other one: 2.4 GHz penetrates walls, 5 GHz is faster near the router.

Commands used hereFlush the DNS cacheRenew the DHCP leaseRestart the Wi-Fi interface

AirPods, mouse, or keyboard lagging over Bluetooth

not urgent
Symptoms

The cursor stutters, headphone audio cuts out, the keyboard drops keystrokes.

What to do

  1. Forget the device in Settings → Bluetooth and pair it again — solves most issues.

  2. Restart the Bluetooth stack without rebooting:

    sudo killall bluetoothd

  3. Remove 2.4 GHz interference sources: USB 3.0 hubs next to the Mac, microwave ovens, congested Wi-Fi.

  4. Switch peripherals to wired or a dongle when working around dozens of Bluetooth devices (office, coworking).

Commands used hereRestart the Bluetooth service

Mac won't sleep or wakes by itself

not urgent
Symptoms

You close the lid — and the Mac keeps working, heating up, and draining in your bag.

What to do

  1. Find the culprit — what's blocking sleep:

    pmset -g assertions

  2. Usual suspects: a forgotten caffeinate, a video player, a call app, a browser with video. Quit the process from the output above.

  3. Check power settings — is a no-sleep mode enabled:

    pmset -g

  4. Disable "Wake for network access" and Power Nap: Settings → Battery/Power Adapter → Options.

  5. Waking at night on a schedule — check Settings → Energy Saver → Schedule.

Commands used hereSee what blocks sleepAll power management settingsPrevent sleep
Might helpAmphetamine

"Your disk is almost full"

gets in the way
Symptoms

macOS warns about low space, the system slows down, updates fail to install.

What to do

  1. Assess the scale — how much is free and where:

    df -h

  2. Find what ate the space: Settings → General → Storage, or visually via DaisyDisk/GrandPerspective.

  3. Developers — start with Xcode's DerivedData (can be tens of GB):

    rm -rf ~/Library/Developer/Xcode/DerivedData

  4. Clean old Homebrew package versions:

    brew cleanup && brew autoremove

  5. Empty the Trash (often holding forgotten gigabytes):

    rm -rf ~/.Trash/*

  6. Uninstall apps completely — via AppCleaner so caches don't linger. Keep at least 10–15% of the disk free.

Commands used hereFree disk spaceClear Xcode DerivedDataClean old versions and dependenciesEmpty the Trash from Terminal
Might helpDaisyDiskGrandPerspectiveAppCleaner

App frozen ("not responding")

not urgent
Symptoms

The rainbow wheel spins forever, the window doesn't react, the Dock shows "not responding".

What to do

  1. Press Cmd+Option+Esc, select the app, and "Force Quit".

  2. Terminal alternative (replace the name):

    killall AppName

  3. If Finder itself froze — right-click its Dock icon while holding Option → Relaunch.

  4. Freezing regularly — check for app updates, or remove it completely with AppCleaner and reinstall.

Commands used hereRestart Finder
Might helpAppCleaner

macOS update stuck

critical
Symptoms

The update progress bar hasn't moved for hours, or the Mac reboots in a loop.

What to do

  1. First — wait. Major updates on a slow disk genuinely take 1–2 hours; a "stuck" bar often lies.

  2. Check the internet and free space: an update needs 15–20 GB and a stable network.

  3. No movement for 3+ hours — force shut down (hold the power button) and boot. The installer resumes where it stopped.

  4. No luck — boot into Safe Mode (Apple Silicon: hold power → Options → Shift + "Continue in Safe Mode") and retry the update.

  5. Last resort — the combo updater from Apple's site or reinstalling macOS via Recovery (data is preserved).

Commands used hereUptime and system load

Mac slow after a macOS update

not urgent
Symptoms

Right after a major update everything is slow, fans are noisy, battery melts.

What to do

  1. This is almost always normal: the system reindexes Spotlight, Photos recognizes faces, iCloud syncs. Give it 1–2 hours (better — overnight on the charger).

  2. Confirm the load comes from system processes:

    ps aux | sort -nrk 3 | head -10

  3. See mds_stores, photoanalysisd, cloudd — just wait, that's background indexing.

  4. Been over a day and still slow — force-reindex Spotlight:

    sudo mdutil -E /

  5. Slowness plus weird glitches — check the disk:

    sudo diskutil verifyVolume /
Commands used hereTop 10 processes by CPU usageUptime and system loadFull Spotlight reindex

Internet works but sites won't open

gets in the way
Symptoms

Messengers work, but the browser shows a DNS error or "site not found".

What to do

  1. Check the internet is alive at all (external IP comes back):

    curl ifconfig.me

  2. Flush the local DNS cache:

    sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

  3. Switch to public DNS servers: Settings → Wi-Fi → Details → DNS → add 1.1.1.1 and 8.8.8.8.

  4. Renew your address from the router:

    sudo ipconfig set en0 DHCP

  5. One specific site won't open — check it from your phone on mobile data: the problem may be on the site's side.

Commands used hereFlush the DNS cacheShow the public IP addressRenew the DHCP lease

Finder won't show thumbnails or previews

not urgent
Symptoms

Generic icons instead of image thumbnails, Quick Look (Space) shows nothing or stale data.

What to do

  1. Reset the QuickLook cache:

    qlmanage -r && qlmanage -r cache

  2. Restart Finder:

    killall Finder

  3. Check folder settings: View → Show View Options → enable "Show icon preview".

  4. Issue only on a network drive — that's a protocol limitation; thumbnails load when the file opens.

Commands used hereReset the QuickLook cacheRestart Finder

"Disk can't be ejected"

not urgent
Symptoms

macOS refuses to unmount a flash drive or external disk — "volume in use by a program".

What to do

  1. Close the obvious: Finder windows on that disk, documents opened from it, and terminals cd'ed into the volume.

  2. Find the process holding the disk (replace NAME with the volume name):

    lsof /Volumes/NAME

  3. Quit the offending process and retry ejecting.

  4. Still stuck — force-eject:

    diskutil eject /Volumes/NAME

  5. Spotlight often holds external drives: add the volume to indexing exclusions (Settings → Spotlight → Search Privacy).

Commands used hereList all disks and partitionsForce-eject a disk

Duplicates in the "Open With" menu

not urgent
Symptoms

The file context menu lists the same app several times.

What to do

  1. That's a bloated LaunchServices database — it duplicates entries after updates and app migrations.

  2. Rebuild the database (single line, takes up to a minute):

    /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain local -domain system -domain user && killall Finder

  3. Duplicates will vanish; custom "always open with…" associations reset to system defaults — reassign them via Cmd+I.

Commands used hereRestart Finder

Battery drains too fast

gets in the way
Symptoms

The MacBook barely makes it to lunch, though it used to last all day.

What to do

  1. Check battery health: Settings → Battery → Battery Health. "Service recommended" — off to service; wear is also visible in coconutBattery.

  2. Find the power-hungry processes:

    ps aux | sort -nrk 3 | head -10

  3. Check what keeps the Mac from idling to sleep:

    pmset -g assertions

  4. Open Settings → Battery: an honest per-app drain chart for the day. Chrome with 50 tabs and video calls are the prime suspects.

  5. Basic hygiene: lower brightness, turn off unused Bluetooth devices, update macOS — updates regularly fix energy leaks.

Commands used hereBattery status from TerminalTop 10 processes by CPU usageSee what blocks sleep
Might helpcoconutBatteryStats
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