# How to build and use it

I'm mostly blindly following information from this guide: https://wiki.ubuntu.com/Kernel/BuildYourOwnKernel

## Enable kernel source fetching

`sudo vim /etc/apt/sources.list` and uncomment these lines:

```
deb-src http://us.archive.ubuntu.com/ubuntu/ bionic main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-updates main restricted
```

```
$ sudo apt update
$ sudo apt-get build-dep linux-image-$(uname -r)
```

## Deps for building the kernel

```
$ sudo apt-get install libncurses-dev libssl-dev libelf-dev gawk
```

## Fetch sources from git and apply this patch

```
$ git clone git://kernel.ubuntu.com/ubuntu/ubuntu-bionic.git
$ cd ubuntu-bionic
$ patch -p1 < ~/Downloads/ubuntu-up-board.patch
```

Note: you may need to edit the first line of `debian.master/changelog`; it looks like this at the time of writing this gist:

```
linux (4.15.0-40.42+upboard) bionic; urgency=medium
```

The `+upboard` part is important and shows up in your `uname -a` output when the kernel is running and disambiguates
your kernel from the official ubuntu packages, however, when I build the kernel it generates an
`linux-image-unsigned-4.15.0-40-generic_4.15.0-40.42+upboard_amd64.deb` package.  The official ubuntu packages
are signed and the package name is `linux-image` instead, so if you have the same version number (aside from the `+upboard`)
as your currently installed kernel, your `linux-image-unsigned` package will conflict with the official `linux-image`
package.   For that reason, I suggest bumping the actual version number as I have done in this gist.

## Build it

This takes a couple of hours on the UP board itself.  You may want to run this on a faster system and then copy the packages
over to your UP board.

Run these steps in your `ubuntu-bionic` git repo:

```
$ fakeroot debian/rules clean
$ fakeroot debian/rules binary-headers binary-generic
```

Once done the parent directory of `ubuntu-bionic` will have a few packages:

```
$ ls ../*.deb -1
../linux-cloud-tools-4.15.0-40-generic_4.15.0-40.42+upboard_amd64.deb
../linux-headers-4.15.0-40-generic_4.15.0-40.42+upboard_amd64.deb
../linux-headers-4.15.0-40_4.15.0-40.42+upboard_all.deb
../linux-image-unsigned-4.15.0-40-generic_4.15.0-40.42+upboard_amd64.deb
../linux-modules-4.15.0-40-generic_4.15.0-40.42+upboard_amd64.deb
../linux-modules-extra-4.15.0-40-generic_4.15.0-40.42+upboard_amd64.deb
../linux-tools-4.15.0-40-generic_4.15.0-40.42+upboard_amd64.deb
```

You only strictly need to install the core kernel and modules:

```
$ cd ..
$ sudo dpkg -i linux-image-unsigned-4.15.0-40-generic_4.15.0-40.42+upboard_amd64.deb \
   linux-modules-4.15.0-40-generic_4.15.0-40.42+upboard_amd64.deb \
   linux-modules-extra-4.15.0-40-generic_4.15.0-40.42+upboard_amd64.deb
```

Then reboot and your should be running your new kernel:

```
$ uname -a
Linux up2 4.15.0-40-generic #42+upboard SMP Wed Nov 21 23:34:11 PST 2018 x86_64 x86_64 x86_64 GNU/Linux
```