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# 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,
)