Building `rootfs.tar.gz`
------------------------

The root filesystem tarball is based on [Gentoo][]'s [amd64
stage3][stage3-amd64] (which we check for a valid [GnuPG
signature][gentoo-signatures]), copying a [minimal
subset](rootfs-files) to the root filesytem, and adding symlinks for
all BusyBox commands. To rebuild the tarball based on a newer stage3,
just run:

```
$ touch get-stage3.sh
$ make rootfs.tar.gz
```

### Getting Gentoo's Release Engineering public key

If `make rootfs.tar.gz` gives an error like:

```
gpg --verify downloads/stage3-amd64-current.tar.bz2.DIGESTS.asc
gpg: Signature made Thu 14 Jan 2016 09:00:11 PM EST using RSA key ID 2D182910
gpg: Can't check signature: public key not found
```

you will need to [add the missing public key to your
keystore][gentoo-signatures].  One way to do that is by [asking a
keyserver][recv-keys]:

```
$ gpg --keyserver pool.sks-keyservers.net --recv-keys 2D182910
```

[Gentoo]: https://www.gentoo.org/
[stage3-amd64]: http://distfiles.gentoo.org/releases/amd64/autobuilds/
[gentoo-signatures]: https://www.gentoo.org/downloads/signatures/
[recv-keys]: https://www.gnupg.org/documentation/manuals/gnupg/Operational-GPG-Commands.html