Skip to content

Instantly share code, notes, and snippets.

@cetinajero

cetinajero/macos_boot_keys.md

Last active September 23, 2026 19:54
Show Gist options

  • Select an option

    Learn more about clone URLs
  • Save cetinajero/ec9fa1d52773c7dcb545e11991f5d17a to your computer and use it in GitHub Desktop.

Select an option

Learn more about clone URLs
Save cetinajero/ec9fa1d52773c7dcb545e11991f5d17a to your computer and use it in GitHub Desktop.
Download ZIP
macOS Boot combination keys and bootable USB commands
Raw
macos_boot_keys.md

macOS Boot combination keys

Keys Description
⌥ Startup Manager
⇧ Safe mode
D Apple Diagnostics
⌥ + D Apple Diagnostics over Internet
⌘ + V Verbose mode
⌘ + S ó ⌘ + R Single-user mode
⌘ + R Install the latest macOS that was installed on your Mac
⌥ + ⌘ + R Upgrade to the latest macOS compatible with your Mac
⇧ + ⌥ + ⌘ + R Install the original macOS, or closest still available
⌥ + ⌘ + P + R Reset NVRAM or PRAM
T Target Disk
⌃ + ⌥ + ⇧ Reset SMC
🚫🔌 + ⏻(10s) + 🔌 + ⏻(10s) + ⏻ Bypass SMC (Don't let go ⏻ for 20s)

Reset a macOS user password

Open the Terminal.app from within macOS Recovery (⌘ + R) and type:

resetpassword

Securely erase a disk

diskutil secureErase 0 /dev/disk4

Download macOS directly from Apple

cd ~/Downloads ; curl -O https://raw.githubusercontent.com/munki/macadmin-scripts/main/installinstallmacos.py ; sudo python installinstallmacos.py

Get the macOS version inside an installer

defaults read /Volumes/Install\ macOS\ */Install\ macOS\ *.app/Contents/Info.plist DTPlatformVersion

Burn a CD/DVD from an ISO9660 ISO file

hdiutil burn image.iso

Burn a USB from an ISOHybrid ISO file

An ISO with a DOS/MBR boot sector is required.

file ubuntu-20.04-desktop-amd64.iso
diskutil unmountDisk /dev/disk2
sudo gdd if=ubuntu-20.04-desktop-amd64.iso of=/dev/rdisk2 bs=4096 status=progress
sudo cmp /dev/disk2 ubuntu-20.04-desktop-amd64.iso

Create a UEFI bootable USB from an ISO file

The /efi/boot/bootx64.efi bootloader is required.

diskutil list
diskutil partitionDisk /dev/disk2 1 MBR FAT32 W10_1909SPA R
hdiutil mount ~/Downloads/Win10_1909_Spanish\(Mexico\)_x64.iso -mountpoint /Volumes/ISO
rsync -avh --info=progress2 /Volumes/ISO/ /Volumes/W10_1909SPA/
diskutil unmountDisk /dev/disk2

Create a MBR bootable USB from an ISO file

Define constants

DEVICE_ID="/dev/disk2"
PART_NAME="W10_2111X64"
ISO_NAME=Win10_21H2_Spanish\(Mexico\)_x64.iso

Format the USB

diskutil list

# diskutil partitionDisk MountPoint [numberOfPartitions] [APM|MBR|GPT] [part1Format[FAT32|ExFAT|JHFS+|APFS|...] part1Name part1Size[%|R] part2Format part2Name part2Size part3Format part3Name part3Size ...]
diskutil partitionDisk $DEVICE_ID 2 MBR FAT32 $PART_NAME $((558 * 100 / 775 + 1))% EXFAT Archivos R

Set the partition as active (boot flag)

(echo flag 1 ; echo write ; echo y ; echo exit) | sudo fdisk -e $DEVICE_ID ; echo

Write the syslinux's MBR (Master Boot Record)

curl https://mirrors.edge.kernel.org/pub/linux/utils/boot/syslinux/syslinux-4.07.tar.gz -o syslinux-4.07.tar.gz
tar -zxvf syslinux-4.07.tar.gz
diskutil unmountDisk $DEVICE_ID
sudo dd if=syslinux-4.07/mbr/mbr.bin of=$DEVICE_ID bs=440 count=1

Write the syslinux's VBR (Volume Boot Record) on an Intel Mac

curl https://raw.githubusercontent.com/unetbootin/unetbootin/master/src/unetbootin/unetbootin.app/Contents/Resources/syslinux-mac -o syslinux-mac
chmod +x syslinux-mac
sudo ./syslinux-mac -i $(echo $DEVICE_ID)s1

Write the syslinux's VBR (Volume Boot Record) on an Apple Silicon Mac

cp syslinux-4.07/core/ldlinux.sys /Volumes/$PART_NAME/

# Calculate ldlinux.sys LBA sector
diskutil unmountDisk $DEVICE_ID
brew install mtools
echo "drive w: file=\"${DEVICE_ID/disk/rdisk}s1\"" > /tmp/mtools.conf
sudo MTOOLSRC=/tmp/mtools.conf minfo w:
# LBA sector = Reserved sectors + (Number of FATs × Sectors per FAT)
# LBA sector = 32 + (2 * 4000) = 8032 = 0x00001F60 = \x60\x1F\x00\x00 (Little Endian)

# Write customized VBR
sudo dd if=${DEVICE_ID/disk/rdisk}s1 of=syslinux-4.07/usb-bpb.bin bs=512 count=1
dd if=syslinux-4.07/core/ldlinux.bss of=syslinux-4.07/usb-bpb.bin bs=1 seek=90 conv=notrunc
printf "\x60\x1F\x00\x00" | dd of=syslinux-4.07/usb-bpb.bin bs=1 seek=504 conv=notrunc
sudo dd if=syslinux-4.07/usb-bpb.bin of=${DEVICE_ID/disk/rdisk}s1 bs=512 count=1 conv=notrunc

# Optionally, set ldlinux.sys FAT attributes (System, Hidden, Read only)
sudo MTOOLSRC=/tmp/mtools.conf mattrib +s +h +r w:/ldlinux.sys
sudo MTOOLSRC=/tmp/mtools.conf mdir w:/
sudo MTOOLSRC=/tmp/mtools.conf mattrib w:/ldlinux.sys

diskutil mountDisk $DEVICE_ID

Write the syslinux's modules (COM32 modules)

mkdir /Volumes/$PART_NAME/syslinux
cp syslinux-4.07/com32/chain/chain.c32 /Volumes/$PART_NAME/syslinux

Write the syslinux's config (syslinux.cfg)

echo -e "DEFAULT boot\n\nLABEL boot\n\tMENU LABEL boot\n\tCOM32 chain.c32\n\tAPPEND fs ntldr=/bootmgr" > /Volumes/$PART_NAME/syslinux/syslinux.cfg

Mount the ISO

hdiutil mount ~/Downloads/$ISO_NAME -mountpoint /Volumes/ISO

Validate if the install.wim file is greater than 4GiB minus 1 byte

if (( `wc -c</Volumes/ISO/sources/install.wim` > 2**32-1 )) ; then echo Exceeds ; fi

Copy the small ISO files to the USB

rsync -avh --info=progress2 --exclude=sources/install.wim /Volumes/ISO/ /Volumes/$PART_NAME/
# or
rsync -avh --progress --exclude=sources/install.wim /Volumes/ISO/ /Volumes/$PART_NAME/
# or
cp -Rpv /Volumes/ISO/ /Volumes/$PART_NAME/

Copy the install.wim file to the USB in smaller parts

brew install wimlib
wimlib-imagex split /Volumes/ISO/sources/install.wim /Volumes/$PART_NAME/sources/install.swm 3800

Unmount the USB

diskutil unmountDisk $DEVICE_ID
# or 
hdiutil unmount /Volumes/$PART_NAME/

Configure Windows Installer to always ask for the version to install

echo -e "[Channel]\nRetail" > /Volumes/$PART_NAME/sources/ei.cfg

Get the Windows activation key from the BIOS

Windows: wmic path softwarelicensingservice get OA3xOriginalProductKey

GNU Linux: sudo hd /sys/firmware/acpi/tables/MSDM

Get the Windows activations status

Use the Server License Manager tool

slmgr /xpr

Install Windows 11 without Internet

  1. Open Task Manager
  • Shift + F10
  • Run taskmgr
  1. End the Network Connection Flow (i.e. Flujo de conexión de red) task several times.

macOS battery monitor

macOS ~/.zshrc

# Sent battery data to a remote server
battery-report() {
  # Print headers
  echo ---Date------Time---Runtime-Condition-Cycles-State-Capacity

  # Record starting time (Epoch time)
  local start_time=$SECONDS

  while true
  do
    # Calculate minutes running
    local runtime=$(( (SECONDS - start_time) / 60 ))

    # Query battery data
    local bat_data=$(system_profiler SPPowerDataType | awk -F: -v hora="$(date +%Y-%m-%d-%H.%M.%S)" -v min="$runtime" '/Full Charge Capacity/ {gsub(/ /,""); cap=$2} /State of Charge/ {gsub(/ /,""); soc=$2} /Cycle Count/ {gsub(/ /,""); cyc=$2} /Condition/ {gsub(/ /,""); cond=$2} END {print hora "-" min "-" cond "-" cyc "-" soc "-" cap}')

    # Print battery data  (eg. 2026-09-23-12.46.27-4-Normal-99-100-7638)
    echo "$bat_data"

    # Send data to HTTP server
    curl -s -o /dev/null -G "http://pbx.grupopv.mx" --data-urlencode "battery-report=$bat_data"

    sleep 10
  done
}

battery-server(){
  while true
  do
    echo -e "HTTP/1.1 200 OK\r\n\r\nOK" | nc -l 4000
  done
}

Apache server

sudo grep battery-report /var/log/apache2/access.log
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment