Buildroot for Android devices

This repository supports the following devices so far:

• Fairphone 2
• Nexus 7 (grouper E1565)
• Lenovo Tab3 7 Essential (TB3-710F, MediaTek MT8127)
• Samsung Galaxy S III Neo (GT-I9301I, s3ve3g, Qualcomm MSM8228): first light and a rescue initramfs
• Samsung Galaxy Express (SGH-I437, expressatt, Qualcomm MSM8960): persistent Linux, USB networking, charging and Wi-Fi scanning; see the board guide.

Fairphone 2

Make sure lk2nd is flashed on the boot partition.

1. Download latest lk2nd image here: lk2nd-msm8974.img
2. Reboot your fp2 in fastboot mode.
3. Run fastboot flash boot lk2nd-msm8974.img
4. Reboot your phone.

Build the buildroot system

1. Run cd buildroot && make BR2_EXTERNAL=../buildroot-external/ fairphone2_defconfig
2. Run make BR2_EXTERNAL=../buildroot-external/ all
3. Reboot your fp2 in fastboot mode.
4. Run fastboot flash userdata output/images/sdcard.img
5. Reboot your phone
6. With your phone plugged to your computer via USB, you should see a new network interface, it should be assigned the 10.0.42.2 ip automatically (the fp2 will be 10.0.42.1)
7. Type ssh root@10.0.42.1, password is root

With U-Boot instead of lk2nd

fairphone2_uboot_defconfig builds U-Boot together with the system and produces output/images/u-boot-fp2.img for the boot partition. fairphone2_uboot_rauc_defconfig adds A/B updates with RAUC, with both root filesystems inside the userdata partition. See docs/fairphone2_uboot.md.

Google Nexus 7 (grouper)

Replace the stock bootloader with Uboot. Follow the instructions here

You will need to recover your SBK with fusee-tools first. You will also need a stock bootloader available, you can find the full image on the google developers website.

Build the buildroot system

1. Run cd buildroot && make BR2_EXTERNAL=../buildroot-external/ grouper_defconfig
2. Run make BR2_EXTERNAL=../buildroot-external/ all
3. Press Volume down then press the power button to get into Uboot's boot menu.
4. Select the UMS option and the device should appear as an external drive on your host computer.
5. Flash the buildroot/output/images/sd_card.img with your favorite tool (Balena etcher works well).
6. Reboot your Nexus 7
7. With your phone plugged to your computer via USB, you should see a new network interface, it should be assigned the 10.0.42.2 ip automatically (the nexus 7 will be 10.0.42.1)
8. Type ssh root@10.0.42.1, password is root

Using WIFI (after flashing)

1. Make sure you can ssh to your FP2 by following the previous section
2. Use nmcli --ask dev wifi connect <YOURSSID>

Using the 4G connection (after flashing and when applicable)

1. Make sure you can ssh to your FP2 by following the instructions above
2. Use nmcli connection add type gsm ifname '*' con-name gsm apn <YOUR APN>
3. Then type nmcli connection up gsm

Lenovo Tab3 7 Essential (TB3-710F)

The stock bootloader (LK) is used as is: it only needs to be unlocked (fastboot oem unlock, then fastboot getvar unlocked says yes). The kernel is mainline Linux 7.3-rc6 plus the patches in buildroot-external/patches/linux/7.3-rc6. More details and the list of what works are in docs/tb3_710f.md.

Build the buildroot system

1. Run cd buildroot && make BR2_EXTERNAL=../buildroot-external/ tb3_710f_defconfig
2. Run make BR2_EXTERNAL=../buildroot-external/ all
3. Reboot your tablet in fastboot mode.
4. Run ../buildroot-external/board/tb3_710f/scripts/flash.sh (flashes output/images/boot.img to the boot partition, only ever talks to the tablet's serial)
5. The first time only, write the root filesystem to the userdata partition, see docs/tb3_710f.md. Until then the tablet boots into a RAM rescue system.
6. With your tablet plugged to your computer via USB, you should see a new network interface, it should be assigned the 10.0.42.2 ip automatically (the tablet will be 10.0.42.1)
7. Type ssh root@10.0.42.1, password is root

Once a system is running, board/tb3_710f/scripts/reflash.sh does the whole cycle (reboot to the bootloader over ssh, flash, wait for ssh).

Samsung Galaxy S III Neo (GT-I9301I, s3ve3g)

The stock Samsung aboot chainloads lk2nd from the BOOT partition (built with an s3ve3g entry); every image is RAM-booted from lk2nd's fastboot. Two RAM-only images exist so far: s3ve3g_firstlight_defconfig and s3ve3g_rescue_defconfig (ssh at 10.0.42.1). Details in docs/s3ve3g.md.

1. Run cd buildroot && make BR2_EXTERNAL=../buildroot-external/ s3ve3g_rescue_defconfig (or s3ve3g_firstlight_defconfig)
2. Run make
3. Start the phone into lk2nd's fastboot menu and run fastboot -s <serial> boot output/images/boot.img