# docker-builder

A small toolchain for setting up, caching and sharing build
environments.

## Existing envs

### [openwrt/](./openwrt/)

For building OpenWrt. Helps you manage build inputs.

See commit 7b2d32b for more details on how to use this, or read on.

#### Setup
TL;DR:

- Fix the value of `$docker_src` in `./docker_vars.sh` and at the top
  of the main Makefile.

- You may also want to tweak `$build_threads`.

- In Docker: Make sure you are using a storage driver (often different
  than the volume driver) big enough to hold the interim build
  process; e.g. overlay2. Default Docker as of Ubuntu 20.04 has a 10G
  limit on volumes.

```json
# /etc/docker/daemon.json
{
	"storage-driver": "overlay2"
}
```

- Make sure you point dockerd somewhere you have sufficient space for
  docker to store images. Example setup, using an override.conf to
  reset ExecStart and point (`-g`) `dockerd` at a 100G-large
  `/dockervl` filesystem:

```txt
$ systemctl cat docker
# /lib/systemd/system/docker.service
# :
# :
# /etc/systemd/system/docker.service.d/override.conf
[Service]
ExecStart=
ExecStart=/usr/bin/dockerd -g /dockervl -H fd:// --containerd=/run/containerd/containerd.sock

[Unit]
After=dockervl.mount
$ sudo df -h /dockervl
Filesystem                 Size  Used Avail Use% Mounted on
/dev/mapper/vg00-dockervl  100G   12G   89G  12% /dockervl
```

#### Usage
- Add new remotes by name-tab-URL to `openwrt-remotes.txt`.

- The main Makefile will manage building containers ('builders'); the
  submakefile in `openwrt/` will deal with actually collecting inputs
  and building.

- Set up the diffconfig and file tree for the target you want to
  build. (The `openwrt/menuconfig-%` target wraps the menuconfig
  OpenWrt target for this purpose; see the next point.)

- Run `make` on the right (.PHONY) target to build the necessary
  containers and e.g. build OpenWrt. The target name is based on the
  action, remote and revision you want; with `$action` being output,
  menuconfig or debug.

- The full name format is: `openwrt/${action}-${remote}_${revision}`,
  where `$remote` is in `openwrt-remotes.txt`, and with `$revision`
  being e.g. a tag, a branch, etc. at the remote you use.

- Additional files can be added under `openwrt/files/`.

- Example run:

```sh
cd ${docker_src}/;
make openwrt/menuconfig-mirror_21.02
# Wait for build and go through menuconfig
# Save the OpenWrt .config file to the default location, then quit.
# Once you quit, the diffconfig will be collected and dropped to output/diffconfig.

cp openwrt/output/diffconfig mr16-for-testing.diffconfig
cp mr16-for-testing.diffconfig openwrt/diffconfig
mkdir -p openwrt/files/etc
touch openwrt/files/etc/hello # This will end up in the image at /etc/hello

# With the diffconfig + files in place:
nohup make openwrt/output-mirror_21.02 &

# Watch the output at:
tail -f openwrt/output/screen.log
```