Firmware Selection and Flashing

This guide covers ImmortalWrt image selection, SD card flashing, and first-boot verification.

Acceptance result: after the Pi has booted for 2–5 minutes, the computer can open http://192.168.1.1.

Pre-flash checks

1. The device is a Raspberry Pi 4B, 400, or CM4.
2. The firmware target is bcm27xx / bcm2711.
3. Existing data on the SD card has been backed up.

Writing an .img or .img.gz replaces the partition table on the card. Verify the target disk by device name and capacity before writing.

Download the correct image

Search for the device in the ImmortalWrt Firmware Selector, or use a project Release explicitly labeled for Raspberry Pi 4B / 400 / CM4.

A first-install disk image commonly ends in .img.gz. Do not download .apk or .ipk package files, and do not mistake a checksum for a firmware image.

EXT4 and SQUASHFS

Writing a fresh disk image overwrites the target card for both types. Configuration retention depends on the backup and upgrade workflow; SQUASHFS does not mean a fresh image automatically preserves old settings.

Recommended method: balenaEtcher

balenaEtcher runs on Windows, macOS, and Linux and normally reads .img.gz directly.

1. Install it from the balenaEtcher website.
2. Select Flash from file and choose the downloaded image.
3. Select the SD card as the target.
4. Confirm the target by capacity and device name.
5. Start flashing and wait for both writing and verification.
6. Safely eject the card.

If Etcher cannot read the compressed image, extract .gz to .img and retry.

Windows notes

Windows may ask to format a partition or say that the drive is inaccessible after flashing. Cancel the prompt. Windows normally cannot read the Linux partitions in the image.

The older Win32 Disk Imager interface looks like this:

When using that tool:

• select the extracted .img, not .gz
• confirm that the drive letter belongs to the SD card
• click Write, not Read

Clicking Read copies the card into the image file. Extract a clean image again and use Write.

macOS: recommended and command-line methods

Prefer balenaEtcher. Use dd only when you understand macOS disk device names.

1. Identify the SD card

Run this before and after inserting the card:

diskutil list

Identify the new disk by capacity, such as /dev/disk6. Do not copy the example number.

2. Unmount it

diskutil unmountDisk /dev/disk6

3. Write the extracted image

sudo dd if=/full/path/immortalwrt.img of=/dev/rdisk6 bs=4m
sync

• if is the image
• of is the whole SD card, not one partition
• /dev/rdiskN is normally faster than /dev/diskN
• press Control + T to ask macOS dd for status

4. Eject it

diskutil eject /dev/disk6

First boot

1. Insert the card while the Pi is powered off.
2. Connect Ethernet; wired access is easier for first-boot troubleshooting.
3. Power on and wait 2–5 minutes.
4. Open http://192.168.1.1.

Wireless defaults can differ between images. A missing SSID is not enough to conclude that flashing failed; test Ethernet first.

Verification

• The flashing tool completed writing and verification
• You did not accept the Windows format prompt
• The activity LED shows card access after power-on
• LuCI opens or the computer receives a network address from the Pi

Continue with first login in the quick start.

Common failures