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Provisioning Bottlerocket on metal

This guide will describe what is needed to properly provision Bottlerocket on bare metal. Provisioning Bottlerocket on metal is different than provisioning other general-purpose distros. Since Bottlerocket has a dm-verity-checked boot and root partition, and is immutable at runtime, a user cannot provision an image and directly write configuration files. Bottlerocket requires a few files to be generated and written to disk at provisioning time in order to boot properly; these files are described below.

For more information about the hardware that Bottlerocket for bare metal is currently tested on, see SUPPORTED-HARDWARE.

High level provisioning steps

The high level steps to provision Bottlerocket images for bare metal to your host are below. Most provisioning systems provide methods to achieve the following:

  • Decompress (unlz4) and write the Bottlerocket image to the desired disk
  • Mount the BOTTLEROCKET-PRIVATE partition (partition 12)
  • Write the below files to the mounted partition (these files are further described below):
  • Reboot

Fetch the Bottlerocket image for bare metal

The Bottlerocket image for bare metal is signed and uploaded alongside the rest of the Bottlerocket release artifacts.

You first need the Bottlerocket root role, which is used by tuftool to verify the image. The following will download and verify the root role itself:

curl -O "https://cache.bottlerocket.aws/root.json"
sha512sum -c <<<"2ff1fbf99b20dd7ff5d2c84243a8e3b51701183b1f524b7d470a6b7a9b0172fbb36a0949b7e586ab7ccb6e348eb77125d6ed9fd1a638f4381e4f3f084ff38596  root.json"

Next, set your desired version and variant, and use tuftool to download the image: To install tuftool you'll need to install Rust (via rustup or the official site), and then you can run cargo install tuftool. The VERSION corresponds to the Bottlerocket version, the latest release is almost always what you want. You might need to install jq to fetch the VERSION.

ARCH="x86_64"
VERSION=$(curl -s https://api.github.com/repos/bottlerocket-os/bottlerocket/releases/latest | jq -r '.name')
VARIANT="metal-k8s-1.28"
IMAGE="bottlerocket-${VARIANT}-${ARCH}-${VERSION}.img.lz4"
OUTDIR="${VARIANT}-${VERSION}"

tuftool download "${OUTDIR}" --target-name "${IMAGE}" \
   --root ./root.json \
   --metadata-url "https://updates.bottlerocket.aws/2020-07-07/${VARIANT}/x86_64/" \
   --targets-url "https://updates.bottlerocket.aws/targets/"

User data

Bottlerocket for bare metal expects a TOML-formatted file named user-data.toml that contains user data settings. Acceptable settings can be found in the settings docs.

If you're just getting started and want to provision a host without connecting to a Kubernetes cluster, you can use the following example user data which will start kubelet in standalone mode.

[settings.kubernetes]
standalone-mode = true

For remote access to your running Bottlerocket hosts, you will need to add user data to enable host containers. The Bottlerocket images for bare metal don't enable any host containers by default. You can use our admin and/or control containers, but they need to be configured first. Full configuration details are covered in the admin container documentation and the control container documentation.

Network interface configuration

Bottlerocket for bare metal provides the means to configure the physical network interfaces in the system via TOML-formatted file net.toml.

net.toml is read at boot time and generates the proper configuration files in the correct format for each interface described; no default configuration is provided. If no network configuration is provided, boot-time services like host containers, containerd, and kubelet will fail to start. When these services fail, your machine will not connect to any cluster and will be unreachable via host containers.

net.toml structure

The configuration file must be valid TOML and have the filename net.toml. The first and required top level key in the file is version; the latest is version 3. The rest of the file is a map of interface name or MAC address to supported settings. Interface names are expected to be correct as per udevd naming, no interface naming or matching is supported. (See the note below regarding udevd interface naming.)

Supported interface settings

  • primary (boolean): Use this interface as the primary network interface. kubelet will use this interface's IP when joining the cluster. If none of the interfaces has primary set, the first interface in the file is used as the primary interface.
  • dhcp4 (boolean or map): Turns on DHCP4 for the interface. If additional DHCP4 configuration is required, the following settings are supported and may be provided as a map with the following keys:
    • enabled (boolean, required): Enables DHCP4.
    • route-metric (integer): Prioritizes routes by setting values for preferred interfaces.
    • optional (boolean): the system will request a lease using this protocol, but will not wait for a valid lease to consider this interface configured.
  • dhcp6 (boolean or map): Turns on DHCP6 for the interface. If additional DHCP6 configuration is required, the following settings are supported and may be provided as a map with the following keys:
    • enabled (boolean, required): Enables DHCP6.
    • optional (boolean): the system will request a lease using this protocol, but will not wait for a valid lease to consider this interface configured.

As of version 2 static addressing with simple routes is supported via the below settings. Please keep in mind that when using static addresses, DNS information must be supplied to the system via user data: settings.dns.

  • static4 (map): IPv4 static address settings.

    • addresses (list of quoted IPv4 address including prefix): The desired IPv4 IP addresses, including prefix i.e. ["192.168.14.2/24"]. The first IP in the list will be used as the primary IP which kubelet will use when joining the cluster. If IPv4 and IPv6 static addresses exist, the first IPv4 address is used.

  • static6 (map): IPv6 static address settings.

    • addresses (list of quoted IPv6 address including prefix): The desired IPv6 IP addresses, including prefix i.e. ["2001:dead:beef::2/64"]. The first IP in the list will be used as the primary IP which kubelet will use when joining the cluster. If IPv4 and IPv6 static addresses exist, the first IPv4 address is used.

  • route (map): Static route; multiple routes can be added. (cannot be used in conjunction with DHCP)

    • to ("default" or IP address with prefix, required): Destination address.
    • from (IP address): Source IP address.
    • via (IP address): Gateway IP address. If no gateway is provided, a scope of link is assumed.
    • route-metric (integer): Relative route priority.

Version 3 adds support for bonding, vlan tagging, and the ability to use a MAC address (colon or dash separated) as the identifier for an interface. MAC address identification is limited to interface configuration only and may not be used in conjunction with bonds or vlans. Bonding support is limited to mode 1 (active-backup). Future support may include other bonding options - pull requests are welcome! Version 3 adds the concept of virtual network devices in addition to interfaces. The default type of device is an interface and the syntax is the same as previous versions. The name of an interface must match an existing interface on the system such as eno1 or enp0s16. For virtual network devices, a kind is required. If no kind is specified, it is assumed to be an interface. Currently, bond and vlan are the two supported kinds. Virtual network devices are created, and therefore a name has to be chosen.

Names for virtual network devices must conform to kernel naming restrictions:

  • Names must not have line terminators in them
  • Names must be between 1-15 characters
  • Names must not contain ., / or whitespace

Bonding configuration creates a virtual network device across several other devices:

  • Bonding configuration (map):
    • kind = "bond": This setting is required to specify a bond device. Required.
    • interfaces (list of quoted strings of interface names, not MAC addresses): Which interfaces should be added to the bond (i.e. ["eno1"]). The first in the list is considered the default primary. These interfaces are "consumed" so no other configuration can refer to them. Required.
    • mode (string): Currently active-backup is the only supported option. Required.
    • min-links (integer): Number of links required to bring up the device
    • monitoring (map): Values m ust all be of miimon or arpmon type. The user must choose one type of monitoring and configure it fully in order for the bond to properly function. See section 7 for more background on what to choose.
      • miimon-frequency-ms (integer): MII Monitoring frequency in milliseconds
      • miimon-updelay-ms (integer): MII Monitoring delay before the link is enabled after link is detected in milliseconds
      • miimon-downdelay-ms (integer): MII Monitoring delay before the link is disabled after link is no longer detected in milliseconds
      • arpmon-interval-ms (integer): Number of milliseconds between intervals to determine link status, must be greater than 0
      • arpmon-validate (one of all, none, active, or backup): What packets should be used to validate link
      • arpmon-targets (list of quoted IPv4 address including prefix): List of targets to use for validating ARP. Min = 1, Max = 16

Vlan tagging is configured as a new virtual network device stacked on another device:

  • Vlan configuration (map):
    • kind = "vlan": This setting is required to specify a vlan device.
    • device (string for device name, not MAC address): Defines the device the vlan should be configured on. If VLAN tagging is required, this device should receive all IP address configuration instead of the underlying device.
    • id (integer): Number between 0 and 4096 specifying the vlan tag on the device

Example net.toml version 3 with comments:

version = 3

# "eno1" is the interface name
[eno1]
# Users may turn on dhcp4 and dhcp6 via boolean
dhcp4 = true
dhcp6 = true
primary = true

# "eno2" is the second interface in this example
[eno2.dhcp4]
# `enabled` is a boolean and is a required key when
# setting up DHCP this way
enabled = true
# Route metric may be supplied for IPv4
route-metric = 200

[eno2.dhcp6]
enabled = true
optional = true

[eno3.static4]
addresses = ["10.0.0.10/24", "11.0.0.11/24"]

# Multiple routes may be configured
[[eno3.route]]
to = "default"
via = "10.0.0.1"
route-metric = 100

[[eno3.route]]
to = "default"
via = "11.0.0.1"
route-metric = 200

[eno4.static4]
addresses = ["192.168.14.5/24"]

# Using a source IP and non-default route
[[eno4.route]]
to = "10.10.10.0/24"
from = "192.168.14.5"
via = "192.168.14.25"

# Interfaces may be configured using their MAC address rather than the interface name.
# The MAC address must be quoted and colon or dash separated
["0e:b3:69:44:b6:33"]
dhcp4 = true

["3e:03:69:49:e6:31".static4]
addresses = ["10.0.0.15/24"]

[["3e:03:69:49:e6:31".route]]
to = "default"
via = "10.0.0.1"

# A bond is a network device that is of `kind` `bond`
[bond0]
kind = "bond"
# Currently `active-backup` is the only supported option
mode = "active-backup"
# In this case, the vlan will have addressing, the bond is simply there for use in the vlan
dhcp4 = false
dhcp6 = false
# The first interface in the array is considered `primary` by default, this list may not contain MAC addresses.
interfaces = ["eno11", "eno12"]

[bond0.monitoring]
miimon-frequency-ms = 100 # 100 milliseconds
miimon-updelay-ms = 200 # 200 milliseconds
miimon-downdelay-ms = 200 # 200 milliseconds

[bond1]
kind = "bond"
mode = "active-backup"
interfaces = ["eno51" , "eno52", "eno53"]
min-links = 2 # Optional min-links 
dhcp4 = true

[bond1.monitoring]
arpmon-interval-ms = 200 # 200 milliseconds
arpmon-validate = "all"
arpmon-targets = ["192.168.1.1", "10.0.0.2"]

# A vlan is a network device that is of `kind` `vlan`
# VLAN42 is the name of the device, can be anything that is a valid network interface name
[VLAN42]
kind = "vlan"
# `device` may not contain a MAC address.
device = "bond0"
id = 42
dhcp4 = true

[internal_vlan]
kind = "vlan"
device = "eno2"
id = 1234
dhcp6 = true

An additional note on network device names

Interface name policies are specified in this file; with name precedence in the following order: onboard, slot, path. Typically on-board devices are named eno*, hot-plug devices are named ens*, and if neither of those names are able to be generated, the “path” name is given, i.e enp*s*f*.

Networking configuration versions and Releases

Older networking configuration versions (such as 1 or 2) are supported in newer releases. In order to use a newer version, the following table provides guidance on what release first enabled the version.

Network Configuration Version First Release
Version 1 v1.9.0
Version 2 v1.10.0
Version 3 v1.12.0

Boot Configuration

Bottlerocket for bare metal uses a feature of the Linux kernel called Boot Configuration, which allows a user to pass additional arguments to the kernel command line at runtime. An immediate use of this feature for most users is setting console settings so boot messages can be seen on the appropriate consoles.

In order to make use of this feature, an initrd is created with the desired settings encoded inside it. The initrd is empty save for the encoded boot config data. To create the initrd, you must first create a configuration file containing key value pairs for the settings you would like to pass to kernel / init. Full syntax is described in the Boot Config documentation, but a simple example is provided below that shows the format of console settings as well as an example systemd parameter.

The two acceptable prefixes to settings are kernel and init. Settings prefixed with kernel are added to the beginning of the kernel command line. Settings prefixed with init are added to the kernel command line after the --, but before any existing init parameters.

In the example below, two console devices are set up, and systemd's log level is set to debug.

Example Boot Configuration:

kernel {
    console = tty0, "ttyS1,115200n8"
}
init {
    systemd.log_level = debug
}

The Bottlerocket SDK provides the bootconfig CLI tool, which is used to create a Boot Configuration initrd. To create the Boot Configuration initrd, create a config file named bootconfig-input containing your desired key/value pair kernel and init arguments.

Then run the following (you will need Docker installed):

ARCH=$(uname -m)
SDK_VERSION="v0.26.0"
SDK_IMAGE="public.ecr.aws/bottlerocket/bottlerocket-sdk-${ARCH}:${SDK_VERSION}"

touch $(pwd)/bootconfig.data

docker run --rm \
   --network=none \
   --user "$(id -u):$(id -g)" \
   --security-opt label=disable \
   -v $(pwd)/bootconfig-input:/tmp/bootconfig-input \
   -v $(pwd)/bootconfig.data:/tmp/bootconfig.data \
   "${SDK_IMAGE}" \
   bootconfig -a /tmp/bootconfig-input /tmp/bootconfig.data

The above command will create the properly named initrd bootconfig.data in your current directory. This is the file you will write to disk during provisioning.

You can list a bootconfig.data's contents, which also validates its format, by running:

ARCH=$(uname -m)
SDK_VERSION="v0.26.0"
SDK_IMAGE="public.ecr.aws/bottlerocket/bottlerocket-sdk-${ARCH}:${SDK_VERSION}"

docker run --rm \
   --network=none \
   --user "$(id -u):$(id -g)" \
   --security-opt label=disable \
   -v $(pwd)/bootconfig.data:/tmp/bootconfig.data \
   "${SDK_IMAGE}" \
   bootconfig -l /tmp/bootconfig.data

Enable Secure Boot

Starting with metal-k8s-1.28, the Bottlerocket images for bare metal support Secure Boot when used on a platform with UEFI firmware. UEFI boot mode must be used, rather than legacy BIOS boot mode, and Secure Boot must be enabled. The UEFI firmware may provide a Compatibility Support Module (CSM) option to enable legacy BIOS emulation. The CSM option must not be enabled. These options can be set in the firmware setup menu, which can be accessed during boot by pressing a certain key (such as F2 or F12).

Many Linux distros ship a copy of the shim bootloader signed by Microsoft with a key that is trusted by default. Although Bottlerocket also uses shim, its copy is not signed by Microsoft and will not be trusted without additional configuration. After installing Bottlerocket, the appropriate vendor certificate can be found on the EFI System Partition (ESP). The firmware setup menu should provide an option to import a new vendor certificate by selecting a file on the ESP. Either the PEM format (db.crt) or DER format (db.cer) certificate can be imported, depending on what the firmware supports.

The firmware setup menu should be password-protected to prevent unauthorized changes to the Secure Boot configuration. Please refer to the documentation from your hardware vendor for more information on this procedure.