musikcube/doc/rpi-buster-chroot.md
casey langen 4f44829cda
Improve cross-compile support (#634)
* Update minimum CMake version requirement to get rid of warning.
* Include CMake compile commands for easier diagnostics.
* More improvements to arm toolchain selection while cross-compiling third-party dependencies.
* Use x-tools provided cmake toolchains
* Add a script to download and extract deb dependencies for crosscompile.
* Link against libstdc++ statically when cross-compiling to ARM to improve portability.
* Update GeneratePackage.cmake to generate better filenames.
* Ensure symbols are stripped properly when cross-compiling
* Remove old scripts that are no longer required
* Add script to install x-tools
* Add some docs that describe how to setup a crosscompile environment.
* Add docs for building standlone on Linux
* Update CHANGELOG
* Update version hash.
2023-09-07 22:05:43 -07:00

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# Forward
- stolen from here: https://medium.com/@crmoratelli/architectural-chroot-for-faster-compilation-and-deployment-on-raspberry-pi-76224327659d
# Install dependencies
- `sudo apt install qemu-kvm qemu-user-static binfmt-support qemu-user-static qemu-utils kpartx e2fsprogs`
# Create a new directory
- `mkdir rpi-buster-chroot`
# Download image
- `wget https://downloads.raspberrypi.org/raspios_oldstable_lite_armhf/images/raspios_oldstable_lite_armhf-2023-05-03/2023-05-03-raspios-buster-armhf-lite.img.xz`
# Extract image
- `xz -d -v 2023-05-03-raspios-buster-armhf-lite.img.xz`
# Expand the image
- `qemu-img resize -f raw 2023-05-03-raspios-buster-armhf-lite.img 16G`
# Expand the partition within the image
- `fdisk 2023-05-03-raspios-buster-armhf-lite.img`
- `Command: p` [prints the partition table. note partition #2's "Start" value.]
- `Command: d` [delete a partition]
- `Command: 2` [delete the Linux partition, which should be #2]
- `Command: n` [add new partition]
- `Command: p` [primary partition]
- `Command: 2` [partition number]
- `Command: ` [enter start value from first step]
- `Command: ` [press enter to accept default value]
- `Command: N` [to *NOT* remove the ext4 signature]
- `Command: w` [write table to file]
# Create a mount point
- `mkdir os-mount`
# Mount both disk imagen partitions via loopback
- `sudo kpartx -a -v 2023-05-03-raspios-buster-armhf-lite.img`
output, note device names:
```
add map loop4p1 (253:0): 0 524288 linear 7:4 8192
add map loop4p2 (253:1): 0 33021952 linear 7:4 532480 <== THIS IS OUR ACTUAL OS
```
# Mount the second partition to the filesystem
- `sudo mount /dev/mapper/loop4p2 ./os-mount`
# Resize the ext filesystem
- `sudo /sbin/resize2fs /dev/mapper/loop4p2`
# Inject qemu and setup special mount points
- `sudo cp /usr/bin/qemu-arm-static ./os-mount/usr/bin`
- `sudo mount -o bind /dev ./os-mount/dev`
- `sudo mount -o bind /proc ./os-mount/proc`
- `sudo mount -o bind /sys ./os-mount/sys`
# Magic: register `qemu-arm-static` as the arm interpreter in the kernel
> Must be root, no `sudo`
- `su`
- `echo ':arm:M::\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff:/usr/bin/qemu-arm-static:' > /proc/sys/fs/binfmt_misc/register`
- `exit`
# Enter the chroot
- `sudo chroot ./os-mount`
# Shutdown
- `sudo umount ./os-mount/dev`
- `sudo umount ./os-mount/proc`
- `sudo umount ./os-mount/sys`
- `sudo umount ./os-mount`
- `sudo kpartx -d -v 2023-05-03-raspios-buster-armhf-lite.img`