Add Alpine Linux support. (#535)

Add new module cc_apk_configure for creating Alpine /etc/apk/repositories file.
Modify cc_ca_certs, cc_ntp, cc_power_state_change, and cc_resolv_conf for Alpine.
Add Alpine template files for Chrony and Busybox NTP support.
Add Alpine template file for /etc/hosts.

8 files changed, 541 insertions, 41 deletions

diff --git a/cloudinit/config/cc_apk_configure.py b/cloudinit/config/cc_apk_configure.py
new file mode 100644
index 00000000..84d7a0b6
--- /dev/null
+++ b/cloudinit/config/cc_apk_configure.py
@@ -0,0 +1,263 @@
+# Copyright (c) 2020 Dermot Bradley
+#
+# Author: Dermot Bradley <dermot_bradley@yahoo.com>
+#
+# This file is part of cloud-init. See LICENSE file for license information.
+
+"""Apk Configure: Configures apk repositories file."""
+
+from textwrap import dedent
+
+from cloudinit import log as logging
+from cloudinit import temp_utils
+from cloudinit import templater
+from cloudinit import util
+from cloudinit.config.schema import (
+    get_schema_doc, validate_cloudconfig_schema)
+from cloudinit.settings import PER_INSTANCE
+
+LOG = logging.getLogger(__name__)
+
+
+# If no mirror is specified then use this one
+DEFAULT_MIRROR = "https://alpine.global.ssl.fastly.net/alpine"
+
+
+REPOSITORIES_TEMPLATE = """\
+## template:jinja
+#
+# Created by cloud-init
+#
+# This file is written on first boot of an instance
+#
+
+{{ alpine_baseurl }}/{{ alpine_version }}/main
+{% if community_enabled -%}
+{{ alpine_baseurl }}/{{ alpine_version }}/community
+{% endif -%}
+{% if testing_enabled -%}
+{% if alpine_version != 'edge' %}
+#
+# Testing - using with non-Edge installation may cause problems!
+#
+{% endif %}
+{{ alpine_baseurl }}/edge/testing
+{% endif %}
+{% if local_repo != '' %}
+
+#
+# Local repo
+#
+{{ local_repo }}/{{ alpine_version }}
+{% endif %}
+
+"""
+
+
+frequency = PER_INSTANCE
+distros = ['alpine']
+schema = {
+    'id': 'cc_apk_configure',
+    'name': 'APK Configure',
+    'title': 'Configure apk repositories file',
+    'description': dedent("""\
+        This module handles configuration of the /etc/apk/repositories file.
+
+        .. note::
+          To ensure that apk configuration is valid yaml, any strings
+          containing special characters, especially ``:`` should be quoted.
+    """),
+    'distros': distros,
+    'examples': [
+        dedent("""\
+        # Keep the existing /etc/apk/repositories file unaltered.
+        apk_repos:
+            preserve_repositories: true
+        """),
+        dedent("""\
+        # Create repositories file for Alpine v3.12 main and community
+        # using default mirror site.
+        apk_repos:
+            alpine_repo:
+                community_enabled: true
+                version: 'v3.12'
+        """),
+        dedent("""\
+        # Create repositories file for Alpine Edge main, community, and
+        # testing using a specified mirror site and also a local repo.
+        apk_repos:
+            alpine_repo:
+                base_url: 'https://some-alpine-mirror/alpine'
+                community_enabled: true
+                testing_enabled: true
+                version: 'edge'
+            local_repo_base_url: 'https://my-local-server/local-alpine'
+        """),
+    ],
+    'frequency': frequency,
+    'type': 'object',
+    'properties': {
+        'apk_repos': {
+            'type': 'object',
+            'properties': {
+                'preserve_repositories': {
+                    'type': 'boolean',
+                    'default': False,
+                    'description': dedent("""\
+                        By default, cloud-init will generate a new repositories
+                        file ``/etc/apk/repositories`` based on any valid
+                        configuration settings specified within a apk_repos
+                        section of cloud config. To disable this behavior and
+                        preserve the repositories file from the pristine image,
+                        set ``preserve_repositories`` to ``true``.
+
+                        The ``preserve_repositories`` option overrides
+                        all other config keys that would alter
+                        ``/etc/apk/repositories``.
+                    """)
+                },
+                'alpine_repo': {
+                    'type': ['object', 'null'],
+                    'properties': {
+                        'base_url': {
+                            'type': 'string',
+                            'default': DEFAULT_MIRROR,
+                            'description': dedent("""\
+                                The base URL of an Alpine repository, or
+                                mirror, to download official packages from.
+                                If not specified then it defaults to ``{}``
+                            """.format(DEFAULT_MIRROR))
+                        },
+                        'community_enabled': {
+                            'type': 'boolean',
+                            'default': False,
+                            'description': dedent("""\
+                                Whether to add the Community repo to the
+                                repositories file. By default the Community
+                                repo is not included.
+                            """)
+                        },
+                        'testing_enabled': {
+                            'type': 'boolean',
+                            'default': False,
+                            'description': dedent("""\
+                                Whether to add the Testing repo to the
+                                repositories file. By default the Testing
+                                repo is not included. It is only recommended
+                                to use the Testing repo on a machine running
+                                the ``Edge`` version of Alpine as packages
+                                installed from Testing may have dependancies
+                                that conflict with those in non-Edge Main or
+                                Community repos."
+                            """)
+                        },
+                        'version': {
+                            'type': 'string',
+                            'description': dedent("""\
+                                The Alpine version to use (e.g. ``v3.12`` or
+                                ``edge``)
+                            """)
+                        },
+                    },
+                    'required': ['version'],
+                    'minProperties': 1,
+                    'additionalProperties': False,
+                },
+                'local_repo_base_url': {
+                    'type': 'string',
+                    'description': dedent("""\
+                        The base URL of an Alpine repository containing
+                        unofficial packages
+                    """)
+                }
+            },
+            'required': [],
+            'minProperties': 1,  # Either preserve_repositories or alpine_repo
+            'additionalProperties': False,
+        }
+    }
+}
+
+__doc__ = get_schema_doc(schema)
+
+
+def handle(name, cfg, cloud, log, _args):
+    """
+    Call to handle apk_repos sections in cloud-config file.
+
+    @param name: The module name "apk-configure" from cloud.cfg
+    @param cfg: A nested dict containing the entire cloud config contents.
+    @param cloud: The CloudInit object in use.
+    @param log: Pre-initialized Python logger object to use for logging.
+    @param _args: Any module arguments from cloud.cfg
+    """
+
+    # If there is no "apk_repos" section in the configuration
+    # then do nothing.
+    apk_section = cfg.get('apk_repos')
+    if not apk_section:
+        LOG.debug(("Skipping module named %s,"
+                   " no 'apk_repos' section found"), name)
+        return
+
+    validate_cloudconfig_schema(cfg, schema)
+
+    # If "preserve_repositories" is explicitly set to True in
+    # the configuration do nothing.
+    if util.get_cfg_option_bool(apk_section, 'preserve_repositories', False):
+        LOG.debug(("Skipping module named %s,"
+                   " 'preserve_repositories' is set"), name)
+        return
+
+    # If there is no "alpine_repo" subsection of "apk_repos" present in the
+    # configuration then do nothing, as at least "version" is required to
+    # create valid repositories entries.
+    alpine_repo = apk_section.get('alpine_repo')
+    if not alpine_repo:
+        LOG.debug(("Skipping module named %s,"
+                   " no 'alpine_repo' configuration found"), name)
+        return
+
+    # If there is no "version" value present in configuration then do nothing.
+    alpine_version = alpine_repo.get('version')
+    if not alpine_version:
+        LOG.debug(("Skipping module named %s,"
+                   " 'version' not specified in alpine_repo"), name)
+        return
+
+    local_repo = apk_section.get('local_repo_base_url', '')
+
+    _write_repositories_file(alpine_repo, alpine_version, local_repo)
+
+
+def _write_repositories_file(alpine_repo, alpine_version, local_repo):
+    """
+    Write the /etc/apk/repositories file with the specified entries.
+
+    @param alpine_repo: A nested dict of the alpine_repo configuration.
+    @param alpine_version: A string of the Alpine version to use.
+    @param local_repo: A string containing the base URL of a local repo.
+    """
+
+    repo_file = '/etc/apk/repositories'
+
+    alpine_baseurl = alpine_repo.get('base_url', DEFAULT_MIRROR)
+
+    params = {'alpine_baseurl': alpine_baseurl,
+              'alpine_version': alpine_version,
+              'community_enabled': alpine_repo.get('community_enabled'),
+              'testing_enabled': alpine_repo.get('testing_enabled'),
+              'local_repo': local_repo}
+
+    tfile = temp_utils.mkstemp(prefix='template_name-', suffix=".tmpl")
+    template_fn = tfile[1]  # Filepath is second item in tuple
+    util.write_file(template_fn, content=REPOSITORIES_TEMPLATE)
+
+    LOG.debug('Generating Alpine repository configuration file: %s',
+              repo_file)
+    templater.render_to_file(template_fn, repo_file, params)
+    # Clean up temporary template
+    util.del_file(template_fn)
+
+
+# vi: ts=4 expandtab
diff --git a/cloudinit/config/cc_ca_certs.py b/cloudinit/config/cc_ca_certs.py
index 910b78de..3c453d91 100644
--- a/cloudinit/config/cc_ca_certs.py
+++ b/cloudinit/config/cc_ca_certs.py
@@ -16,11 +16,16 @@ can be removed from the system with the configuration option
     certificates must be specified using valid yaml. in order to specify a
     multiline certificate, the yaml multiline list syntax must be used
 
+.. note::
+    For Alpine Linux the "remove-defaults" functionality works if the
+    ca-certificates package is installed but not if the
+    ca-certificates-bundle package is installed.
+
 **Internal name:** ``cc_ca_certs``
 
 **Module frequency:** per instance
 
-**Supported distros:** ubuntu, debian
+**Supported distros:** alpine, debian, ubuntu
 
 **Config keys**::
 
@@ -45,7 +50,7 @@ CA_CERT_CONFIG = "/etc/ca-certificates.conf"
 CA_CERT_SYSTEM_PATH = "/etc/ssl/certs/"
 CA_CERT_FULL_PATH = os.path.join(CA_CERT_PATH, CA_CERT_FILENAME)
 
-distros = ['ubuntu', 'debian']
+distros = ['alpine', 'debian', 'ubuntu']
 
 
 def update_ca_certs():
@@ -83,7 +88,7 @@ def add_ca_certs(certs):
         util.write_file(CA_CERT_CONFIG, out, omode="wb")
 
 
-def remove_default_ca_certs():
+def remove_default_ca_certs(distro_name):
     """
     Removes all default trusted CA certificates from the system. To actually
     apply the change you must also call L{update_ca_certs}.
@@ -91,11 +96,14 @@ def remove_default_ca_certs():
     util.delete_dir_contents(CA_CERT_PATH)
     util.delete_dir_contents(CA_CERT_SYSTEM_PATH)
     util.write_file(CA_CERT_CONFIG, "", mode=0o644)
-    debconf_sel = "ca-certificates ca-certificates/trust_new_crts select no"
-    subp.subp(('debconf-set-selections', '-'), debconf_sel)
+
+    if distro_name != 'alpine':
+        debconf_sel = (
+            "ca-certificates ca-certificates/trust_new_crts " + "select no")
+        subp.subp(('debconf-set-selections', '-'), debconf_sel)
 
 
-def handle(name, cfg, _cloud, log, _args):
+def handle(name, cfg, cloud, log, _args):
     """
     Call to handle ca-cert sections in cloud-config file.
 
@@ -117,7 +125,7 @@ def handle(name, cfg, _cloud, log, _args):
     # default trusted CA certs first.
     if ca_cert_cfg.get("remove-defaults", False):
         log.debug("Removing default certificates")
-        remove_default_ca_certs()
+        remove_default_ca_certs(cloud.distro.name)
 
     # If we are given any new trusted CA certs to add, add them.
     if "trusted" in ca_cert_cfg:
diff --git a/cloudinit/config/cc_ntp.py b/cloudinit/config/cc_ntp.py
index 7d3f73ff..3d7279d6 100644
--- a/cloudinit/config/cc_ntp.py
+++ b/cloudinit/config/cc_ntp.py
@@ -24,7 +24,8 @@ LOG = logging.getLogger(__name__)
 frequency = PER_INSTANCE
 NTP_CONF = '/etc/ntp.conf'
 NR_POOL_SERVERS = 4
-distros = ['centos', 'debian', 'fedora', 'opensuse', 'rhel', 'sles', 'ubuntu']
+distros = ['alpine', 'centos', 'debian', 'fedora', 'opensuse', 'rhel',
+           'sles', 'ubuntu']
 
 NTP_CLIENT_CONFIG = {
     'chrony': {
@@ -63,6 +64,17 @@ NTP_CLIENT_CONFIG = {
 
 # This is Distro-specific configuration overrides of the base config
 DISTRO_CLIENT_CONFIG = {
+    'alpine': {
+        'chrony': {
+            'confpath': '/etc/chrony/chrony.conf',
+            'service_name': 'chronyd',
+        },
+        'ntp': {
+            'confpath': '/etc/ntp.conf',
+            'packages': [],
+            'service_name': 'ntpd',
+        },
+    },
     'debian': {
         'chrony': {
             'confpath': '/etc/chrony/chrony.conf',
@@ -114,11 +126,11 @@ schema = {
         Handle ntp configuration. If ntp is not installed on the system and
         ntp configuration is specified, ntp will be installed. If there is a
         default ntp config file in the image or one is present in the
-        distro's ntp package, it will be copied to ``/etc/ntp.conf.dist``
-        before any changes are made. A list of ntp pools and ntp servers can
-        be provided under the ``ntp`` config key. If no ntp ``servers`` or
-        ``pools`` are provided, 4 pools will be used in the format
-        ``{0-3}.{distro}.pool.ntp.org``."""),
+        distro's ntp package, it will be copied to a file with ``.dist``
+        appended to the filename before any changes are made. A list of ntp
+        pools and ntp servers can be provided under the ``ntp`` config key.
+        If no ntp ``servers`` or ``pools`` are provided, 4 pools will be used
+        in the format ``{0-3}.{distro}.pool.ntp.org``."""),
     'distros': distros,
     'examples': [
         dedent("""\
@@ -171,7 +183,10 @@ schema = {
                     'description': dedent("""\
                         List of ntp pools. If both pools and servers are
                         empty, 4 default pool servers will be provided of
-                        the format ``{0-3}.{distro}.pool.ntp.org``.""")
+                        the format ``{0-3}.{distro}.pool.ntp.org``. NOTE:
+                        for Alpine Linux when using the Busybox NTP client
+                        this setting will be ignored due to the limited
+                        functionality of Busybox's ntpd.""")
                 },
                 'servers': {
                     'type': 'array',
@@ -364,21 +379,30 @@ def generate_server_names(distro):
     """
     names = []
     pool_distro = distro
-    # For legal reasons x.pool.sles.ntp.org does not exist,
-    # use the opensuse pool
+
     if distro == 'sles':
+        # For legal reasons x.pool.sles.ntp.org does not exist,
+        # use the opensuse pool
         pool_distro = 'opensuse'
+    elif distro == 'alpine':
+        # Alpine-specific pool (i.e. x.alpine.pool.ntp.org) does not exist
+        # so use general x.pool.ntp.org instead.
+        pool_distro = ''
+
     for x in range(0, NR_POOL_SERVERS):
-        name = "%d.%s.pool.ntp.org" % (x, pool_distro)
-        names.append(name)
+        names.append(".".join(
+            [n for n in [str(x)] + [pool_distro] + ['pool.ntp.org'] if n]))
+
     return names
 
 
-def write_ntp_config_template(distro_name, servers=None, pools=None,
-                              path=None, template_fn=None, template=None):
+def write_ntp_config_template(distro_name, service_name=None, servers=None,
+                              pools=None, path=None, template_fn=None,
+                              template=None):
     """Render a ntp client configuration for the specified client.
 
     @param distro_name: string.  The distro class name.
+    @param service_name: string. The name of the NTP client service.
     @param servers: A list of strings specifying ntp servers. Defaults to empty
     list.
     @param pools: A list of strings specifying ntp pools. Defaults to empty
@@ -397,7 +421,14 @@ def write_ntp_config_template(distro_name, servers=None, pools=None,
     if not pools:
         pools = []
 
-    if len(servers) == 0 and len(pools) == 0:
+    if (len(servers) == 0 and distro_name == 'alpine' and
+            service_name == 'ntpd'):
+        # Alpine's Busybox ntpd only understands "servers" configuration
+        # and not "pool" configuration.
+        servers = generate_server_names(distro_name)
+        LOG.debug(
+            'Adding distro default ntp servers: %s', ','.join(servers))
+    elif len(servers) == 0 and len(pools) == 0:
         pools = generate_server_names(distro_name)
         LOG.debug(
             'Adding distro default ntp pool servers: %s', ','.join(pools))
@@ -532,6 +563,8 @@ def handle(name, cfg, cloud, log, _args):
             raise RuntimeError(msg)
 
     write_ntp_config_template(cloud.distro.name,
+                              service_name=ntp_client_config.get(
+                                  'service_name'),
                               servers=ntp_cfg.get('servers', []),
                               pools=ntp_cfg.get('pools', []),
                               path=ntp_client_config.get('confpath'),
diff --git a/cloudinit/config/cc_power_state_change.py b/cloudinit/config/cc_power_state_change.py
index 41ffb46c..ab953a0d 100644
--- a/cloudinit/config/cc_power_state_change.py
+++ b/cloudinit/config/cc_power_state_change.py
@@ -22,9 +22,8 @@ The ``delay`` key specifies a duration to be added onto any shutdown command
 used. Therefore, if a 5 minute delay and a 120 second shutdown are specified,
 the maximum amount of time between cloud-init starting and the system shutting
 down is 7 minutes, and the minimum amount of time is 5 minutes. The ``delay``
-key must have an argument in a form that the ``shutdown`` utility recognizes.
-The most common format is the form ``+5`` for 5 minutes. See ``man shutdown``
-for more options.
+key must have an argument in either the form ``+5`` for 5 minutes or ``now``
+for immediate shutdown.
 
 Optionally, a command can be run to determine whether or not
 the system should shut down. The command to be run should be specified in the
@@ -33,6 +32,10 @@ the system should shut down. The command to be run should be specified in the
 ``condition`` key is omitted or the command specified by the ``condition``
 key returns 0.
 
+.. note::
+    With Alpine Linux any message value specified is ignored as Alpine's halt,
+    poweroff, and reboot commands do not support broadcasting a message.
+
 **Internal name:** ``cc_power_state_change``
 
 **Module frequency:** per instance
@@ -112,9 +115,9 @@ def check_condition(cond, log=None):
         return False
 
 
-def handle(_name, cfg, _cloud, log, _args):
+def handle(_name, cfg, cloud, log, _args):
     try:
-        (args, timeout, condition) = load_power_state(cfg)
+        (args, timeout, condition) = load_power_state(cfg, cloud.distro.name)
         if args is None:
             log.debug("no power_state provided. doing nothing")
             return
@@ -141,7 +144,19 @@ def handle(_name, cfg, _cloud, log, _args):
                  condition, execmd, [args, devnull_fp])
 
 
-def load_power_state(cfg):
+def convert_delay(delay, fmt=None, scale=None):
+    if not fmt:
+        fmt = "+%s"
+    if not scale:
+        scale = 1
+
+    if delay != "now":
+        delay = fmt % int(int(delay) * int(scale))
+
+    return delay
+
+
+def load_power_state(cfg, distro_name):
     # returns a tuple of shutdown_command, timeout
     # shutdown_command is None if no config found
     pstate = cfg.get('power_state')
@@ -161,20 +176,34 @@ def load_power_state(cfg):
             (','.join(opt_map.keys()), mode))
 
     delay = pstate.get("delay", "now")
-    # convert integer 30 or string '30' to '+30'
+    message = pstate.get("message")
+    scale = 1
+    fmt = "+%s"
+    command = ["shutdown", opt_map[mode]]
+
+    if distro_name == 'alpine':
+        # Convert integer 30 or string '30' to '1800' (seconds) as Alpine's
+        # halt/poweroff/reboot commands take seconds rather than minutes.
+        scale = 60
+        # No "+" in front of delay value as not supported by Alpine's commands.
+        fmt = "%s"
+        if delay == "now":
+            # Alpine's commands do not understand "now".
+            delay = "0"
+        command = [mode, "-d"]
+        # Alpine's commands don't support a message.
+        message = None
+
     try:
-        delay = "+%s" % int(delay)
+        delay = convert_delay(delay, fmt=fmt, scale=scale)
     except ValueError:
-        pass
-
-    if delay != "now" and not re.match(r"\+[0-9]+", delay):
         raise TypeError(
             "power_state[delay] must be 'now' or '+m' (minutes)."
             " found '%s'." % delay)
 
-    args = ["shutdown", opt_map[mode], delay]
-    if pstate.get("message"):
-        args.append(pstate.get("message"))
+    args = command + [delay]
+    if message:
+        args.append(message)
 
     try:
         timeout = float(pstate.get('timeout', 30.0))
diff --git a/cloudinit/config/cc_resolv_conf.py b/cloudinit/config/cc_resolv_conf.py
index 69f4768a..519e66eb 100644
--- a/cloudinit/config/cc_resolv_conf.py
+++ b/cloudinit/config/cc_resolv_conf.py
@@ -30,7 +30,7 @@ are configured correctly.
 
 **Module frequency:** per instance
 
-**Supported distros:** fedora, rhel, sles
+**Supported distros:** alpine, fedora, rhel, sles
 
 **Config keys**::
 
@@ -55,7 +55,7 @@ LOG = logging.getLogger(__name__)
 
 frequency = PER_INSTANCE
 
-distros = ['fedora', 'opensuse', 'rhel', 'sles']
+distros = ['alpine', 'fedora', 'opensuse', 'rhel', 'sles']
 
 
 def generate_resolv_conf(template_fn, params, target_fname="/etc/resolv.conf"):
diff --git a/cloudinit/distros/__init__.py b/cloudinit/distros/__init__.py
index c7163e1c..effb4276 100755
--- a/cloudinit/distros/__init__.py
+++ b/cloudinit/distros/__init__.py
@@ -40,12 +40,13 @@ from .networking import LinuxNetworking
 ALL_DISTROS = 'all'
 
 OSFAMILIES = {
+    'alpine': ['alpine'],
+    'arch': ['arch'],
     'debian': ['debian', 'ubuntu'],
-    'redhat': ['amazon', 'centos', 'fedora', 'rhel'],
-    'gentoo': ['gentoo'],
     'freebsd': ['freebsd'],
+    'gentoo': ['gentoo'],
+    'redhat': ['amazon', 'centos', 'fedora', 'rhel'],
     'suse': ['opensuse', 'sles'],
-    'arch': ['arch'],
 }
 
 LOG = logging.getLogger(__name__)
diff --git a/cloudinit/distros/alpine.py b/cloudinit/distros/alpine.py
new file mode 100644
index 00000000..e42443fc
--- /dev/null
+++ b/cloudinit/distros/alpine.py
@@ -0,0 +1,165 @@
+# Copyright (C) 2016 Matt Dainty
+# Copyright (C) 2020 Dermot Bradley
+#
+# Author: Matt Dainty <matt@bodgit-n-scarper.com>
+# Author: Dermot Bradley <dermot_bradley@yahoo.com>
+#
+# This file is part of cloud-init. See LICENSE file for license information.
+
+from cloudinit import distros
+from cloudinit import helpers
+from cloudinit import log as logging
+from cloudinit import subp
+from cloudinit import util
+
+from cloudinit.distros.parsers.hostname import HostnameConf
+
+from cloudinit.settings import PER_INSTANCE
+
+LOG = logging.getLogger(__name__)
+
+NETWORK_FILE_HEADER = """\
+# This file is generated from information provided by the datasource. Changes
+# to it will not persist across an instance reboot. To disable cloud-init's
+# network configuration capabilities, write a file
+# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
+# network: {config: disabled}
+
+"""
+
+
+class Distro(distros.Distro):
+    init_cmd = ['rc-service']  # init scripts
+    locale_conf_fn = "/etc/profile.d/locale.sh"
+    network_conf_fn = "/etc/network/interfaces"
+    renderer_configs = {
+        "eni": {"eni_path": network_conf_fn,
+                "eni_header": NETWORK_FILE_HEADER}
+    }
+
+    def __init__(self, name, cfg, paths):
+        distros.Distro.__init__(self, name, cfg, paths)
+        # This will be used to restrict certain
+        # calls from repeatly happening (when they
+        # should only happen say once per instance...)
+        self._runner = helpers.Runners(paths)
+        self.default_locale = 'C.UTF-8'
+        self.osfamily = 'alpine'
+        cfg['ssh_svcname'] = 'sshd'
+
+    def get_locale(self):
+        """The default locale for Alpine Linux is different than
+           cloud-init's DataSource default.
+        """
+        return self.default_locale
+
+    def apply_locale(self, locale, out_fn=None):
+        # Alpine has limited locale support due to musl library limitations
+
+        if not locale:
+            locale = self.default_locale
+        if not out_fn:
+            out_fn = self.locale_conf_fn
+
+        lines = [
+            "#",
+            "# This file is created by cloud-init once per new instance boot",
+            "#",
+            "export CHARSET=UTF-8",
+            "export LANG=%s" % locale,
+            "export LC_COLLATE=C",
+            "",
+        ]
+        util.write_file(out_fn, "\n".join(lines), 0o644)
+
+    def install_packages(self, pkglist):
+        self.update_package_sources()
+        self.package_command('add', pkgs=pkglist)
+
+    def _write_network_config(self, netconfig):
+        return self._supported_write_network_config(netconfig)
+
+    def _bring_up_interfaces(self, device_names):
+        use_all = False
+        for d in device_names:
+            if d == 'all':
+                use_all = True
+        if use_all:
+            return distros.Distro._bring_up_interface(self, '-a')
+        else:
+            return distros.Distro._bring_up_interfaces(self, device_names)
+
+    def _write_hostname(self, your_hostname, out_fn):
+        conf = None
+        try:
+            # Try to update the previous one
+            # so lets see if we can read it first.
+            conf = self._read_hostname_conf(out_fn)
+        except IOError:
+            pass
+        if not conf:
+            conf = HostnameConf('')
+        conf.set_hostname(your_hostname)
+        util.write_file(out_fn, str(conf), 0o644)
+
+    def _read_system_hostname(self):
+        sys_hostname = self._read_hostname(self.hostname_conf_fn)
+        return (self.hostname_conf_fn, sys_hostname)
+
+    def _read_hostname_conf(self, filename):
+        conf = HostnameConf(util.load_file(filename))
+        conf.parse()
+        return conf
+
+    def _read_hostname(self, filename, default=None):
+        hostname = None
+        try:
+            conf = self._read_hostname_conf(filename)
+            hostname = conf.hostname
+        except IOError:
+            pass
+        if not hostname:
+            return default
+        return hostname
+
+    def _get_localhost_ip(self):
+        return "127.0.1.1"
+
+    def set_timezone(self, tz):
+        distros.set_etc_timezone(tz=tz, tz_file=self._find_tz_file(tz))
+
+    def package_command(self, command, args=None, pkgs=None):
+        if pkgs is None:
+            pkgs = []
+
+        cmd = ['apk']
+        # Redirect output
+        cmd.append("--quiet")
+
+        if args and isinstance(args, str):
+            cmd.append(args)
+        elif args and isinstance(args, list):
+            cmd.extend(args)
+
+        if command:
+            cmd.append(command)
+
+        pkglist = util.expand_package_list('%s-%s', pkgs)
+        cmd.extend(pkglist)
+
+        # Allow the output of this to flow outwards (ie not be captured)
+        subp.subp(cmd, capture=False)
+
+    def update_package_sources(self):
+        self._runner.run("update-sources", self.package_command,
+                         ["update"], freq=PER_INSTANCE)
+
+    @property
+    def preferred_ntp_clients(self):
+        """Allow distro to determine the preferred ntp client list"""
+        if not self._preferred_ntp_clients:
+            self._preferred_ntp_clients = ['chrony', 'ntp']
+
+        return self._preferred_ntp_clients
+
+# vi: ts=4 expandtab
diff --git a/cloudinit/util.py b/cloudinit/util.py
index edd37039..dd263803 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -548,7 +548,8 @@ def system_info():
     if system == "linux":
         linux_dist = info['dist'][0].lower()
         if linux_dist in (
-                'arch', 'centos', 'debian', 'fedora', 'rhel', 'suse'):
+                'alpine', 'arch', 'centos', 'debian', 'fedora', 'rhel',
+                'suse'):
             var = linux_dist
         elif linux_dist in ('ubuntu', 'linuxmint', 'mint'):
             var = 'ubuntu'