Bootstrapping Servers

Kolla-ansible provides support for bootstrapping host configuration prior to deploying containers via the bootstrap-servers subcommand. This includes support for the following:

  • Customisation of /etc/hosts

  • Creation of user and group

  • Kolla configuration directory

  • Package installation and removal

  • Docker engine installation and configuration

  • Disabling firewalls

  • Creation of Python virtual environment

  • Configuration of Apparmor

  • Configuration of SELinux

  • Configuration of NTP daemon

All bootstrapping support is provided by the baremetal Ansible role.

Running the command

The base command to perform a bootstrap is:

kolla-ansible bootstrap-servers -i INVENTORY

Further options may be necessary, as described in the following sections.

Initial bootstrap considerations

The nature of bootstrapping means that the environment that Ansible executes in during the initial bootstrap may look different to that seen after bootstrapping is complete. For example:

  • The kolla_user user account may not yet have been created. If this is normally used as the ansible_user when executing Kolla Ansible, a different user account must be used for bootstrapping.

  • The Python virtual environment may not exist. If a virtualenv is normally used as the ansible_python_interpreter when executing Kolla Ansible, the system python interpreter must be used for bootstrapping.

Each of these variables may be passed via the -e argument to Kolla Ansible to override the inventory defaults:

kolla-ansible bootstrap-servers -i INVENTORY -e ansible_user=<bootstrap user> -e ansible_python_interpreter=/usr/bin/python

Subsequent bootstrap considerations

It is possible to run the bootstrapping process against a cloud that has already been bootstrapped, for example to apply configuration from a newer release of Kolla Ansible. In this case, further considerations should be made.

It is possible that the Docker engine package will be updated. This will cause the Docker engine to restart, in addition to all running containers. There are three main approaches to avoiding all control plane services restarting simultaneously.

The first option is to use the --limit command line argument to apply the command to hosts in batches, ensuring there is always a quorum for clustered services (e.g. MariaDB):

kolla-ansible bootstrap-servers -i INVENTORY --limit controller0,compute[0-1]
kolla-ansible bootstrap-servers -i INVENTORY --limit controller1,compute[2-3]
kolla-ansible bootstrap-servers -i INVENTORY --limit controller2,compute[4-5]

The second option is to execute individual plays on hosts in batches:

kolla-ansible bootstrap-servers -i INVENTORY -e kolla_serial=30%

The last option is to use the Docker live-restore configuration option to avoid restarting containers when the Docker engine is restarted. There have been issues reported with using this option however, so use it at your own risk.

Ensure that any operation that causes the Docker engine to be updated has been tested, particularly when moving from legacy Docker packages to Docker Community Edition. See Package repositories for details.

Customisation of /etc/hosts

This is optional, and enabled by customize_etc_hosts, which is true by default.

  • Ensures that localhost is in /etc/hosts

  • Adds an entry for the IP of the API interface of each host to /etc/hosts.

Creation of user and group

This is optional, and enabled by create_kolla_user, which is true by default.

  • Ensures that a group exists with the name defined by the variable kolla_group with default kolla.

  • Ensures that a user exists with the name defined by the variable kolla_user with default kolla. The user’s primary group is defined by kolla_group. The user is added to the sudo group.

  • An SSH public key is authorised for kolla_user. The key is defined by the public_key value of the kolla_ssh_key mapping variable, typically defined in passwords.yml.

  • If the create_kolla_user_sudoers variable is set, a sudoers profile will be configured for kolla_user, which grants passwordless sudo.

Kolla configuration directory

Kolla ansible service configuration is written to hosts in a directory defined by node_config_directory, which by default is /etc/kolla/. This directory will be created. If create_kolla_user is set, the owner and group of the directory will be set to kolla_user and kolla_group respectively.

Package installation and removal

Lists of packages are defined for installation and removal. On Debian family systems, these are defined by debian_pkg_install and ubuntu_pkg_removals respectively. On Red Hat family systems, these are defined by redhat_pkg_install and redhat_pkg_removals respectively.

Docker engine installation and configuration

Docker engine is a key dependency of Kolla Ansible, and various configuration options are provided.

Package repositories

If the enable_docker_repo flag is set, then a package repository for Docker packages will be configured. Kolla Ansible uses the ‘Community Edition’ packages from https://download.docker.com.

Various other configuration options are available beginning docker_(apt|yum)_. Typically these do not need to be changed.

Configuration

The docker_storage_driver variable is optional. If set, it defines the storage driver to use for Docker.

The docker_runtime_directory variable is optional. If set, it defines the runtime (data-root) directory for Docker.

The docker_registry variable, which is not set by default, defines the address of the Docker registry. If the variable is not set, Dockerhub will be used.

The docker_registry_insecure variable, which defaults to true if docker_registry is set, or false otherwise, defines whether to configure docker_registry as an insecure registry. Insecure registries use HTTP rather than HTTPS.

The docker_log_max_file variable, which defaults to 5, defines the maximum number of log files to retain per container. The docker_log_max_size variable, which defaults to 50m, defines the maximum size of each rotated log file per container.

Additional options for the Docker engine can be passed in docker_custom_config variable. It will be stored in daemon.json config file. Example:

{
    "experimental": false
}

Disabling firewalls

Kolla Ansible does not support configuration of host firewalls, and instead attempts to disable them.

On Debian family systems where the UFW firewall is enabled, a default policy will be added to allow all traffic.

On Red Hat family systems where firewalld is installed, it will be disabled.

Creation of Python virtual environment

This is optional, and enabled by setting virtualenv to a path to a Python virtual environment to create. By default, a virtual environment is not used. If virtualenv_site_packages is set, (default is true) the virtual environment will inherit packages from the global site-packages directory. This is typically required for modules such as yum and apt which are not available on PyPI. See Target Hosts for further information.

Configuration of Apparmor

On Ubuntu systems, the libvirtd Apparmor profile will be removed.

Configuration of SELinux

On Red Hat family systems, if change_selinux is set (default is true), then the SELinux state will be set to selinux_state (default permissive). See Kolla Security for further information.

Configuration of NTP daemon

This is optional, and enabled by enable_host_ntp, which is false by default.