Netboot describes the means of booting a device when the rootfs is not on the device but accessed via network, in this implementation via USB networking.
Make sure your kernel has the necessary kernel config options for netboot.
$ pmbootstrap kconfig check --netboot $kernel-package-name
If not you need to adjust your kernel config otherwise netboot won't work.
First prepare a rootfs for your device. It is advisable to use the
--extra-space argument to increase the size of your rootfs (in the example you will get 1000MB of extra space) as no image resize will happen at runtime. Also, some devices are configured to be flashed with a sparse image, but that is not compatible with netboot currently.
$ pmbootstrap --extra-space 1000 install --no-sparse
Then prepare your boot.img and flash it to the device:
$ pmbootstrap initfs hook_add netboot $ pmbootstrap flasher boot # or however you flash/boot the kernel
After booting the device a network interface should appear over USB networking.
Finally you need to start the netboot server on your computer with the following command:
$ pmbootstrap netboot serve
Make sure to open up tcp port 9999 on your computer's firewall so the phone can connect to your netboot service.
If you've never used netboot for the current device, then the image from the previous
pmbootstrap install will get copied to
$pmbootstrap_work/images_netboot/ and will persist normal
pmbootstrap zap calls as you will probably have data in your rootfs.
Note: For android devices, you may need to run
fastboot erase dtbo before flashing/booting the kernel. If you are running an a/b slot device, make sure to add the correct suffix (dtbo_a or dtbo_b).
Replacing persisted rootfs
You can replace the persisted rootfs image with a fresh image from
$ pmbootstrap netboot serve --replace
Deleting all netboot images
You can delete all persisted rootfs images:
$ pmbootstrap zap --netboot
Resizing a netboot image
When you run out of space in your netbooted rootfs, you can increase the size of the image!
The following example increases the size of the image
fairphone-fp4.img by 1 GiB.
$ cd ~/.local/var/pmbootstrap/images_netboot/ $ sudo bash -c "dd if=/dev/zero bs=1M count=1000 >> ./fairphone-fp4.img" $ sudo parted ./fairphone-fp4.img (parted) resizepart 2 100% (parted) quit $ sudo losetup --find --show --partscan ./fairphone-fp4.img $ sudo e2fsck -f /dev/loop0p2 # verify that you will be operating on the correct loop device! $ sudo resize2fs /dev/loop0p2 $ sudo losetup --detach /dev/loop0
- tuxphones: You can now live-boot postmarketOS on Android phones, great article describing what the feature is and how it was implemented
As of 01/31/2022, there are a couple known issues:
- The initfs netboot hook currently expects a boot sector size of 512 bytes, but many android devices may be configured with a sector size of 4096 using the
deviceinfo_rootfs_image_sector_sizeproperty. This will give an error like "unable to find boot partition". Using debug-shell (add to install with
pmbootstrap initfs hook_add debug-shell) to modify the
/etc/postmarketos-mkinitfs/hook/netboot.shfile and setting the nbd-client sector size to 4096 should fix this.
- Some android devices may set
deviceinfo_flash_sparseto true and this causes the generated block device to be unusable by netboot. You can pass "--no-sparse" to your
pmbootstrap installcommand to override this.