Source : https://cyberblogspot.com/how-to-save-and-restore-esp8266-and-esp32-firmware/
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Gathering the Board’s Info esptool.py flash_id
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Save 1MByte or 8Mbit Flash esptool.py --baud 115200 --port COM8 read_flash 0x0 0x100000 fw-backup-1M.bin
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Save 4MByte or 32Mbit Flash