This repository contains CzechLight-specific bits for Buildroot. Buildroot is a tool which produces system images for flashing to embedded devices. They have a nice documentation which explains everything that one might need.
Everything is in Gerrit. One should not need to clone anything from anywhere else. The build will download source tarballs of various open source components, though. The following branches are required:
| Project | branch |
|---|---|
| github/buildroot/buildroot | cesnet/cla-6 |
| CzechLight/br2-external | master |
Our SW uses several open-source projects which are special snowflakes and which are integrated by the CI due to their tight coupling:
TODO: Can we use git submodules instead of this madness? Will that work reasonably well for changes that need to be made in a lockstep?
TODO: Automate this via the CI system. I want to get the .img files for testing of each change, eventually.
The commit hashes (SHA1s) of the required versions are stored in git. All of these projects have to be checked out and made available to Buildroot via a local.mk file in the build dir:
#DOCOPT_CPP_OVERRIDE_SRCDIR = /home/cesnet/gerrit/github/docopt/docopt.cpp #SPDLOG_OVERRIDE_SRCDIR = /home/cesnet/gerrit/github/gabime/spdlog LIBYANG_OVERRIDE_SRCDIR = /home/cesnet/gerrit/github/CESNET/libyang SYSREPO_OVERRIDE_SRCDIR = /home/cesnet/gerrit/github/sysrepo/sysrepo LIBNETCONF2_OVERRIDE_SRCDIR = /home/cesnet/gerrit/github/CESNET/libnetconf2 NETOPEER2_KEYSTORED_OVERRIDE_SRCDIR = /home/cesnet/gerrit/github/CESNET/Netopeer2 NETOPEER2_SERVER_OVERRIDE_SRCDIR = /home/cesnet/gerrit/github/CESNET/Netopeer2 NETOPEER2_CLI_OVERRIDE_SRCDIR = /home/cesnet/gerrit/github/CESNET/Netopeer2 CLA_SYSREPO_OVERRIDE_SRCDIR = /home/cesnet/gerrit/CzechLight/cla-sysrepo
For each of these projects, clone them from Gerrit and then checkout a specific Git ref. The command might be something like:
git checkout -b wip || git checkout wip git fetch git reset --hard SHA_GOES_HERE
This local.mk instructs Buildroot to skip download of these critical packages from the Internet. Their sources will be used as-is from these source directories. No patches will be applied!
mkdir build-for-clearfog cd build-for-clearfog vim local.mk # ...edit as shown above... make O=$PWD -C /home/cesnet/gerrit/github/buildroot/buildroot \ BR2_EXTERNAL=/home/cesnet/gerrit/CzechLight/br2-external \ czechlight_clearfog_defconfig make
A full rebuild takes between 30 and 45 minutes on a T460s laptop for targets which use a pre-generated Linaro toolchain (clearfog, beaglebone). Other targets take longer because one has to build a toolchain first. When the build finishes, the generated image to be dd-ed to an SD card is at images/sdcard.img.
WARNING: Buildroot is fragile. It is not safe to perform incremental builds after changing an "important" setting. Please check their manual for details. Using ccache might help, but a significant time is wasted in configure steps which are not parallelized :( as of October 2017.
Apart from the traditional way of re-flashing the SD card or the eMMC from scratch, it's also possible to use RAUC to update. This method preserves the U-Boot version and the U-Boot's environment. Apart from that, everything starting with the kernel and the DTB file and including the root FS is updated.
FIXME: the system uses separate config partitions (/cfg), so these persistent bits are not preserved yet (see these user stories).
To install an update:
# build node make rsync -avP images/update.raucb somewhere.example.org:path/to/web/root # target, perhaps via an USB console wget http://somewhere.example.org/update.raucb -O /tmp/update.raucb rauc install /tmp/update.raucb reboot