🛠 Sauver une Zero qui ne boot plus : le flux legacy sans EEPROM

Goal

Recover a Zero that stopped booting after a bad config.txt or a corrupted filesystem. Key fact: the Zero has no EEPROM (unlike Pi 4/5). The legacy boot flow is plain files on the FAT partition — bootcode.bin, start.elf, config.txt — so recovery means editing files, never reflashing firmware.

Boot anatomy

One bad overlay line = black screen. The fix is always: mount the card on another machine.

1. The BCM2835 reads the microSD FAT partition and runs bootcode.bin.
2. bootcode.bin loads start.elf (GPU), which parses config.txt.
3. The kernel starts with cmdline.txt ; the root filesystem mounts after 'rootwait'.

Repair

sudo mkdir -p /mnt/sdboot && sudo mount /dev/sdX1 /mnt/sdboot
ls /mnt/sdboot        # bootcode.bin, start.elf, config.txt, cmdline.txt

# Comment out the last config.txt edits:
sudo sed -i 's/^dtoverlay=dwc2/# &/' /mnt/sdboot/config.txt

# cmdline.txt must be ONE line and must keep rootwait:
cat /mnt/sdboot/cmdline.txt

# Filesystem errors? fsck the UNMOUNTED root partition:
sudo umount /dev/sdX2 2>/dev/null; sudo fsck -y /dev/sdX2

If the card is beyond repair, rewrite the image with Raspberry Pi Imager — there is nothing on the board itself to reflash.

Check

Card back in the Zero: mini-HDMI output returns and SSH works again ; vcgencmd versioncheck reports on-or-after-date boot files.

Pitfalls

• Hunting for an EEPROM recovery mode as on Pi 4/5: it does not exist — everything lives on the card.
• Editing from Windows: only the small FAT partition is visible ; that is exactly where config.txt is.
• fsck on a mounted partition: unmount first or you deepen the corruption.
• Chronic corruption usually means a weak supply: the Zero gives no undervoltage warning.