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hosts.rst 21.72 KiB

Host Configuration

This section covers configuration of hosts. It does not cover configuration or deployment of containers. Hosts that are configured by Kayobe include:

  • Seed hypervisor (kayobe seed hypervisor host configure)
  • Seed (kayobe seed host configure)
  • Overcloud (kayobe overcloud host configure)

Unless otherwise stated, all host configuration described here is applied to each of these types of host.

Configuration Location

Some host configuration options are set via global variables, and others have a variable for each type of host. The latter variables are included in the following files under ${KAYOBE_CONFIG_PATH}:

  • seed-hypervisor.yml
  • seed.yml
  • compute.yml
  • controller.yml
  • monitoring.yml
  • storage.yml

Note that any variable may be set on a per-host or per-group basis, by using inventory host or group variables - these delineations are for convenience.

Paths

Several directories are used by Kayobe on the remote hosts. There is a hierarchy of variables in ${KAYOBE_CONFIG_PATH}/globals.yml that can be used to control where these are located.

  • base_path (default /opt/kayobe/) sets the default base path for various directories.
  • config_path (default {{ base_path }}/etc) is a path in which to store configuration files.
  • image_cache_path (default {{ base_path }}/images) is a path in which to cache downloaded or built images.
  • source_checkout_path (default {{ base_path }}/src) is a path into which to store clones of source code repositories.
  • virtualenv_path (default {{ base_path }}/venvs) is a path in which to create Python virtual environments.

SSH Known Hosts

tags:
ssh-known-host

While strictly this configuration is applied to the Ansible control host (localhost), it is applied during the host configure commands. The ansible_host of each host is added as an SSH known host. This is typically the host's IP address on the admin network (admin_oc_net_name), as defined in ${KAYOBE_CONFIG_PATH}/network-allocation.yml (see :ref:`configuration-network-ip-allocation`).

Kayobe User Bootstrapping

tags:
kayobe-ansible-user

Kayobe uses a user account defined by the kayobe_ansible_user variable (in ${KAYOBE_CONFIG_PATH}/globals.yml) for remote SSH access. By default, this is stack.

Typically, the image used to provision these hosts will not include this user account, so Kayobe performs a bootstrapping step to create it, as a different user. In cloud images, there is often a user named after the OS distro, e.g. centos or ubuntu. This user defaults to the name of the user running Kayobe, but may be set via the following variables:

  • seed_hypervisor_bootstrap_user
  • seed_bootstrap_user
  • compute_bootstrap_user
  • controller_bootstrap_user
  • monitoring_bootstrap_user
  • storage_bootstrap_user

For example, to set the bootstrap user for controllers to centos:

PyPI Mirror and proxy

tags:
pip

Kayobe supports configuration of a PyPI mirror and/or proxy, via variables in ${KAYOBE_CONFIG_PATH}/pip.yml. Mirror functionality is enabled by setting the pip_local_mirror variable to true and proxy functionality is enabled by setting pip_proxy variable to a proxy URL.

Kayobe will generate configuration for:

  • pip to use the mirror and proxy
  • easy_install to use the mirror

for the list of users defined by pip_applicable_users (default kayobe_ansible_user and root), in addition to the user used for Kolla Ansible (kolla_ansible_user). The mirror URL is configured via pip_index_url, and pip_trusted_hosts is a list of 'trusted' hosts, for which SSL verification will be disabled.

For example, to configure use of the test PyPI mirror at https://test.pypi.org/simple/:

To configure use of the PyPI proxy:

Kayobe Remote Virtual Environment

tags:
kayobe-target-venv

By default, Ansible executes modules remotely using the system python interpreter, even if the Ansible control process is executed from within a virtual environment (unless the local connection plugin is used). This is not ideal if there are python dependencies that must be installed with isolation from the system python packages. Ansible can be configured to use a virtualenv by setting the host variable ansible_python_interpreter to a path to a python interpreter in an existing virtual environment.

If kayobe detects that ansible_python_interpreter is set and references a virtual environment, it will create the virtual environment if it does not exist. Typically this variable should be set via a group variable in the inventory for hosts in the seed, seed-hypervisor, and/or overcloud groups.

The default Kayobe configuration in the kayobe-config repository sets ansible_python_interpreter to {{ virtualenv_path }}/kayobe/bin/python for the seed, seed-hypervisor, and overcloud groups.

Disk Wiping

tags:
wipe-disks

Using hosts that may have stale data on their disks could affect the deployment of the cloud. This is not a configuration option, since it should only be performed once to avoid losing useful data. It is triggered by passing the --wipe-disks argument to the host configure commands.

Users and Groups

tags:
users

Linux user accounts and groups can be configured using the users_default variable in ${KAYOBE_CONFIG_PATH}/users.yml. The format of the list is that used by the users variable of the singleplatform-eng.users role. The following variables can be used to set the users for specific types of hosts:

  • seed_hypervisor_users
  • seed_users
  • compute_users
  • controller_users
  • monitoring_users
  • storage_users

In the following example, a single user named bob is created. A password hash has been generated via mkpasswd --method=sha-512. The user is added to the wheel group, and an SSH key is authorised. The SSH public key should be added to the Kayobe configuration.

Package Repositories

tags:
yum

Kayobe supports configuration of package repositories via Yum, via variables in ${KAYOBE_CONFIG_PATH}/yum.yml.

Configuration of yum.conf

Global configuration of Yum is stored in /etc/yum.conf, and options can be set via the yum_config variable. Options are added to the [main] section of the file. For example, to configure Yum to use a proxy server:

CentOS and EPEL Mirrors

CentOS and EPEL mirrors can be enabled by setting yum_use_local_mirror to true. CentOS repository mirrors are configured via the following variables:

  • yum_centos_mirror_host (default mirror.centos.org) is the mirror hostname.
  • yum_centos_mirror_directory (default centos) is a directory on the mirror in which repositories may be accessed.

EPEL repository mirrors are configured via the following variables:

  • yum_epel_mirror_host (default download.fedoraproject.org) is the mirror hostname.
  • yum_epel_mirror_directory (default pub/epel) is a directory on the mirror in which repositories may be accessed.

For example, to configure CentOS and EPEL mirrors at mirror.example.com:

Custom Yum Repositories

It is also possible to configure a list of custom Yum repositories via the yum_custom_repos variable. The format is a dict/map, with repository names mapping to a dict/map of arguments to pass to the Ansible yum module.

For example, the following configuration defines a single Yum repository called widgets.

Disabling EPEL

It is possible to disable the EPEL Yum repository by setting yum_install_epel to false.

SELinux

tags:
disable-selinux

SELinux is not supported by Kolla Ansible currently, so it is disabled by Kayobe. If necessary, Kayobe will reboot systems in order to apply a change to the SELinux configuration. The timeout for waiting for systems to reboot is disable_selinux_reboot_timeout. Alternatively, the reboot may be avoided by setting disable_selinux_do_reboot to false.

Network Configuration

tags:
network

Configuration of host networking is covered in depth in :ref:`configuration-network`.

Sysctls

tags:
sysctl

Arbitrary sysctl configuration can be applied to hosts. The variable format is a dict/map, mapping parameter names to their required values. The following variables can be used to set sysctl configuration specific types of hosts:

  • seed_hypervisor_sysctl_parameters
  • seed_sysctl_parameters
  • compute_sysctl_parameters
  • controller_sysctl_parameters
  • monitoring_sysctl_parameters
  • storage_sysctl_parameters

For example, to set the net.ipv4.ip_forward parameter to 1 on controllers:

Disable cloud-init

tags:
disable-cloud-init

cloud-init is a popular service for performing system bootstrapping. If you are not using cloud-init, this section can be skipped.

If using the seed's Bifrost service to provision the control plane hosts, the use of cloud-init may be configured via the kolla_bifrost_dib_init_element variable.

cloud-init searches for network configuration in order of increasing precedence; each item overriding the previous. In some cases, on subsequent boots cloud-init can automatically reconfigure network interfaces and cause some issues in network configuration. To disable cloud-init from running after the initial server bootstrapping, set disable_cloud_init to true in ${KAYOBE_CONFIG_PATH}/overcloud.yml.

Disable Glean

tags:
disable-glean

The glean service can be used to perform system bootstrapping, serving a similar role to cloud-init. If you are not using glean, this section can be skipped.

If using the seed's Bifrost service to provision the control plane hosts, the use of glean may be configured via the kolla_bifrost_dib_init_element variable.

After the initial server bootstrapping, the glean service can cause problems as it attempts to enable all network interfaces, which can lead to timeouts while booting. To avoid this, the glean service is disabled. Additionally, any network interface configuration files generated by glean and not overwritten by Kayobe are removed.

Timezone

tags:
ntp

The timezone can be configured via the timezone variable in ${KAYOBE_CONFIG_PATH}/ntp.yml. The value must be a valid Linux timezone. For example:

NTP

tags:
ntp

Network Time Protocol (NTP) may be configured via variables in ${KAYOBE_CONFIG_PATH}/ntp.yml. The list of NTP servers is configured via ntp_config_server, and by default the pool.ntp.org servers are used. A list of restrictions may be added via ntp_config_restrict, and a list of interfaces to listen on via ntp_config_listen. Other options and their default values may be found in the resmo.ntp Ansible role.

The NTP service may be disabled as follows:

Chrony

Kolla Ansible can deploy a chrony container. This is disabled by default in Kayobe to avoid conflicting with the NTP daemon on the host.

To use the containerised chrony daemon and disable the host NTP daemon, set the following in ${KAYOBE_CONFIG_PATH}/kolla.yml:

kolla_enable_chrony: true

Software RAID

tags:
mdadm

While it is possible to use RAID directly with LVM, some operators may prefer the userspace tools provided by mdadm or may have existing software RAID arrays they want to manage with Kayobe.

Software RAID arrays may be configured via the mdadm_arrays variable. For convenience, this is mapped to the following variables:

  • seed_hypervisor_mdadm_arrays
  • seed_mdadm_arrays
  • compute_mdadm_arrays
  • controller_mdadm_arrays
  • monitoring_mdadm_arrays
  • storage_mdadm_arrays

The format of these variables is as defined by the mdadm_arrays variable of the mrlesmithjr.mdadm Ansible role.

For example, to configure two of the seed's disks as a RAID1 mdadm array available as /dev/md0:

LVM

tags:
lvm

Logical Volume Manager (LVM) physical volumes, volume groups, and logical volumes may be configured via the lvm_groups variable. For convenience, this is mapped to the following variables:

  • seed_hypervisor_lvm_groups
  • seed_lvm_groups
  • compute_lvm_groups
  • controller_lvm_groups
  • monitoring_lvm_groups
  • storage_lvm_groups

The format of these variables is as defined by the lvm_groups variable of the mrlesmithjr.manage-lvm Ansible role.

LVM for libvirt

LVM is not configured by default on the seed hypervisor. It is possible to configure LVM to provide storage for a libvirt storage pool, typically mounted at /var/lib/libvirt/images.

To use this configuration, set the seed_hypervisor_lvm_groups variable to "{{ seed_hypervisor_lvm_groups_with_data }}" and provide a list of disks via the seed_hypervisor_lvm_group_data_disks variable.

LVM for Docker

The default LVM configuration is optimised for the devicemapper Docker storage driver, which requires a thin provisioned LVM volume. A second logical volume is used for storing Docker volume data, mounted at /var/lib/docker/volumes. Both logical volumes are created from a single data volume group.

To use this configuration, a list of disks must be configured via the following variables:

  • seed_lvm_group_data_disks
  • compute_lvm_group_data_disks
  • controller_lvm_group_data_disks
  • monitoring_lvm_group_data_disks
  • storage_lvm_group_data_disks

For example, to configure two of the seed's disks for use by LVM:

The Docker volumes LVM volume is assigned a size given by the following variables, with a default value of 75% (of the volume group's capacity):

  • seed_lvm_group_data_lv_docker_volumes_size
  • compute_lvm_group_data_lv_docker_volumes_size
  • controller_lvm_group_data_lv_docker_volumes_size
  • monitoring_lvm_group_data_lv_docker_volumes_size
  • storage_lvm_group_data_lv_docker_volumes_size

If using a Docker storage driver other than devicemapper, the remaining 25% of the volume group can be used for Docker volume data. In this case, the LVM volume's size can be increased to 100%:

If using a Docker storage driver other than devicemapper, it is possible to avoid using LVM entirely, thus avoiding the requirement for multiple disks. In this case, set the appropriate <host>_lvm_groups variable to an empty list:

Custom LVM