[Starlingx-discuss] Build installer instructions

[Cordoba Malibran, Erich]

Hi, 

I would like to share/discuss the instructions to generate the
installer before are publish into the wiki. I couldn't find a previous
version of these instructions, probably I confused with this warning
from the download_mirror.sh[0]. The update-pxe-network-installer script
follows the steps detailed here[1].

Build installer
===============

To get your StarlingX ISO ready to use, you will need to create the
init files that will be used to boot the ISO as well to boot additional
controllers and compute nodes.

Once you had run `build-iso`, run:

```
build-pkgs --installer
```

This will build `rpm` and `anaconda` packages. Then run:

```
update-pxe-network-installer
```

The update-pxe-network-installer` covers the steps detailed in
`$MY_REPO/stx/stx-metal/installer/initrd/README`. This script will
create three files on `/localdisk/loadbuild/<user>/<project>/pxe-
network-installer/output`

```
new-initrd.img
new-squashfs.img
new-vmlinuz
```

Then, rename them to:

```
initrd.img-stx-0.2
squashfs.img-stx-0.2
vmlinuz-stx-0.2
```

There are two ways to use these files:

1. Store the files in the '/import/mirror/CentOS/tis-installer/`
folder  for future use.
2. Store it in an arbitrary location and modify the `$MY_REPO/stx/stx-
metal/installer/pxe-network-installer/centos/build_srpm.data` file to
point to these files.

Now, the `pxe-network-installer` package needs to be recreated and the
ISO regenerated.

```
build-pkgs --clean pxe-network-installer
build-pkgs pxe-network-installer
build-iso
```

Now your ISO should be able to boot. 

Updating these files is not a common tasks, it is recommended only do
it if the kernel version is upgraded or new kernel modules are added.


=====================
End of documentation



[0] http://git.starlingx.io/cgit/stx-tools/tree/centos-mirror-tools/download_mirror.sh#n264
[1] http://git.starlingx.io/cgit/stx-metal/tree/installer/initrd/README