docs: details on building rootfs

Mention the ability to use devtool to automate the steps of building a Firecracker tailored disk image. Signed-off-by: Diana Popa <[email protected]>
firecracker-microvm · Aug 26, 2021 · 4001cbd · 4001cbd
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diff --git a/docs/getting-started.md b/docs/getting-started.md
@@ -85,10 85,10 @@ file system image (to use as rootfs).
 
 1. To run an `x86_64` guest you can download such resources from:
  [kernel](https://s3.amazonaws.com/spec.ccfc.min/img/quickstart_guide/x86_64/kernels/vmlinux.bin)
- and [rootfs](https://s3.amazonaws.com/spec.ccfc.min/img/hello/fsfiles/hello-rootfs.ext4).
  and [rootfs](https://s3.amazonaws.com/spec.ccfc.min/img/quickstart_guide/x86_64/rootfs/bionic.rootfs.ext4).
 1. To run an `aarch64` guest, download them from:
  [kernel](https://s3.amazonaws.com/spec.ccfc.min/img/quickstart_guide/aarch64/kernels/vmlinux.bin)
- and [rootfs](https://s3.amazonaws.com/spec.ccfc.min/img/aarch64/ubuntu_with_ssh/fsfiles/xenial.rootfs.ext4).
  and [rootfs](https://s3.amazonaws.com/spec.ccfc.min/img/quickstart_guide/aarch64/rootfs/bionic.rootfs.ext4).
 
 Now, let's open up two shell prompts: one to run Firecracker, and another one
 to control it (by writing to the API socket). For the purpose of this guide,
@@ -117,14 117,14 @@ In your **second shell** prompt:
  arch=`uname -m`
  dest_kernel="hello-vmlinux.bin"
  dest_rootfs="hello-rootfs.ext4"
- image_bucket_url="https://s3.amazonaws.com/spec.ccfc.min/img"
  image_bucket_url="https://s3.amazonaws.com/spec.ccfc.min/img/quickstart_guide/$arch"
 
  if [ ${arch} = "x86_64" ]; then
- kernel="${image_bucket_url}/quickstart_guide/x86_64/kernels/vmlinux.bin"
- rootfs="${image_bucket_url}/hello/fsfiles/hello-rootfs.ext4"
  kernel="${image_bucket_url}/kernels/vmlinux.bin"
  rootfs="${image_bucket_url}/rootfs/bionic.rootfs.ext4"
  elif [ ${arch} = "aarch64" ]; then
- kernel="${image_bucket_url}/quickstart_guide/aarch64/kernels/vmlinux.bin"
- rootfs="${image_bucket_url}/aarch64/ubuntu_with_ssh/fsfiles/xenial.rootfs.ext4"
  kernel="${image_bucket_url}/kernels/vmlinux.bin"
  rootfs="${image_bucket_url}/rootfs/bionic.rootfs.ext4"
  else
  echo "Cannot run firecracker on $arch architecture!"
  exit 1

diff --git a/docs/rootfs-and-kernel-setup.md b/docs/rootfs-and-kernel-setup.md
@@ -76,7 76,10 @@ OpenRC as an init system. Note that, whichever file system you choose to use,
 support for it will have to be compiled into the kernel, so it can be mounted
 at boot time.
 
-To build an EXT4 image:
 In order to obtain an EXT4 image that you can use with Firecracker, you have
 the following options:
 
 ### Manual build
 
 1. Prepare a properly-sized file. We'll use 50MiB here, but this depends
  on how much data you'll want to fit inside:
@@ -158,5 161,23 @@ Alpine Linux:
  sudo umount /tmp/my-rootfs
  ```
 
 ### Use the provided recipe
 
 The disk images used in our CI to test Firecracker's features are obtained by
 using the recipe inside devtool:
 
 ```bash
 ./tools/devtool build_rootfs -s 300
 ```
 
 or
 
 ```bash
 ./tools/devtool build_rootfs -p
 ```
 
 in order to obtain a partuuid enabled rootfs.
 The images resulting using this method are minimized Ubuntu 18.04.
 
 You should now have a kernel image (`vmlinux`) and a rootfs image
 (`rootfs.ext4`), that you can boot with Firecracker.