name : cc_update_etc_hosts.py # Copyright (C) 2011 Canonical Ltd. # Copyright (C) 2012 Hewlett-Packard Development Company, L.P. # # Author: Scott Moser <scott.moser@canonical.com> # Author: Juerg Haefliger <juerg.haefliger@hp.com> # # This file is part of cloud-init. See LICENSE file for license information. """Update Etc Hosts: Update the hosts file (usually ``/etc/hosts``)""" import logging from textwrap import dedent from cloudinit import templater, util from cloudinit.cloud import Cloud from cloudinit.config import Config from cloudinit.config.schema import MetaSchema, get_meta_doc from cloudinit.settings import PER_ALWAYS MODULE_DESCRIPTION = """\ This module will update the contents of the local hosts database (hosts file; usually ``/etc/hosts``) based on the hostname/fqdn specified in config. Management of the hosts file is controlled using ``manage_etc_hosts``. If this is set to false, cloud-init will not manage the hosts file at all. This is the default behavior. If set to ``true``, cloud-init will generate the hosts file using the template located in ``/etc/cloud/templates/hosts.tmpl``. In the ``/etc/cloud/templates/hosts.tmpl`` template, the strings ``$hostname`` and ``$fqdn`` will be replaced with the hostname and fqdn respectively. If ``manage_etc_hosts`` is set to ``localhost``, then cloud-init will not rewrite the hosts file entirely, but rather will ensure that a entry for the fqdn with a distribution dependent ip is present (i.e. ``ping <hostname>`` will ping ``127.0.0.1`` or ``127.0.1.1`` or other ip). .. note:: if ``manage_etc_hosts`` is set ``true``, the contents of the hosts file will be updated every boot. To make any changes to the hosts file persistent they must be made in ``/etc/cloud/templates/hosts.tmpl`` .. note:: for instructions on specifying hostname and fqdn, see documentation for ``cc_set_hostname`` """ distros = ["all"] meta: MetaSchema = { "id": "cc_update_etc_hosts", "name": "Update Etc Hosts", "title": "Update the hosts file (usually ``/etc/hosts``)", "description": MODULE_DESCRIPTION, "distros": distros, "examples": [ dedent( """\ # Do not update or manage /etc/hosts at all. This is the default behavior. # # Whatever is present at instance boot time will be present after boot. # User changes will not be overwritten. manage_etc_hosts: false """ ), dedent( """\ # Manage /etc/hosts with cloud-init. # On every boot, /etc/hosts will be re-written from # ``/etc/cloud/templates/hosts.tmpl``. # # The strings '$hostname' and '$fqdn' are replaced in the template # with the appropriate values either from the config-config ``fqdn`` or # ``hostname`` if provided. When absent, the cloud metadata will be # checked for ``local-hostname` which can be split into <hostname>.<fqdn>. # # To make modifications persistent across a reboot, you must modify # ``/etc/cloud/templates/hosts.tmpl``. manage_etc_hosts: true """ ), dedent( """\ # Update /etc/hosts every boot providing a "localhost" 127.0.1.1 entry # with the latest hostname and fqdn as provided by either IMDS or # cloud-config. # All other entries will be left as is. # 'ping `hostname`' will ping 127.0.1.1 manage_etc_hosts: localhost """ ), ], "frequency": PER_ALWAYS, "activate_by_schema_keys": ["manage_etc_hosts"], } __doc__ = get_meta_doc(meta) LOG = logging.getLogger(__name__) def handle(name: str, cfg: Config, cloud: Cloud, args: list) -> None: manage_hosts = util.get_cfg_option_str(cfg, "manage_etc_hosts", False) hosts_fn = cloud.distro.hosts_fn if util.translate_bool(manage_hosts, addons=["template"]): if manage_hosts == "template": util.deprecate( deprecated="Value 'template' for key 'manage_etc_hosts'", deprecated_version="22.2", extra_message="Use 'true' instead.", ) (hostname, fqdn, _) = util.get_hostname_fqdn(cfg, cloud) if not hostname: LOG.warning( "Option 'manage_etc_hosts' was set, but no hostname was found" ) return # Render from a template file tpl_fn_name = cloud.get_template_filename( "hosts.%s" % (cloud.distro.osfamily) ) if not tpl_fn_name: raise RuntimeError( "No hosts template could be found for distro %s" % (cloud.distro.osfamily) ) templater.render_to_file( tpl_fn_name, hosts_fn, {"hostname": hostname, "fqdn": fqdn} ) elif manage_hosts == "localhost": (hostname, fqdn, _) = util.get_hostname_fqdn(cfg, cloud) if not hostname: LOG.warning( "Option 'manage_etc_hosts' was set, but no hostname was found" ) return LOG.debug("Managing localhost in %s", hosts_fn) cloud.distro.update_etc_hosts(hostname, fqdn) else: LOG.debug( "Configuration option 'manage_etc_hosts' is not set," " not managing %s in module %s", hosts_fn, name, )