merge from trunk

9 files changed, 766 insertions, 238 deletions

diff --git a/cloudinit/distros/__init__.py b/cloudinit/distros/__init__.py
index 8a98e334..10e07e82 100644
--- a/cloudinit/distros/__init__.py
+++ b/cloudinit/distros/__init__.py
@@ -24,6 +24,7 @@
 from StringIO import StringIO
 
 import abc
+import collections
 import itertools
 import os
 import re
@@ -33,11 +34,16 @@ from cloudinit import log as logging
 from cloudinit import ssh_util
 from cloudinit import util
 
+from cloudinit.distros.parsers import hosts
+
 LOG = logging.getLogger(__name__)
 
 
 class Distro(object):
     __metaclass__ = abc.ABCMeta
+    hosts_fn = "/etc/hosts"
+    ci_sudoers_fn = "/etc/sudoers.d/90-cloud-init-users"
+    hostname_conf_fn = "/etc/hostname"
 
     def __init__(self, name, cfg, paths):
         self._paths = paths
@@ -57,13 +63,10 @@ class Distro(object):
     def get_option(self, opt_name, default=None):
         return self._cfg.get(opt_name, default)
 
-    @abc.abstractmethod
     def set_hostname(self, hostname, fqdn=None):
-        raise NotImplementedError()
-
-    @abc.abstractmethod
-    def update_hostname(self, hostname, fqdn, prev_hostname_fn):
-        raise NotImplementedError()
+        writeable_hostname = self._select_hostname(hostname, fqdn)
+        self._write_hostname(writeable_hostname, self.hostname_conf_fn)
+        self._apply_hostname(hostname)
 
     @abc.abstractmethod
     def package_command(self, cmd, args=None):
@@ -87,7 +90,7 @@ class Distro(object):
 
     def get_package_mirror_info(self, arch=None,
                                 availability_zone=None):
-        # this resolves the package_mirrors config option
+        # This resolves the package_mirrors config option
         # down to a single dict of {mirror_name: mirror_url}
         arch_info = self._get_arch_package_mirror_info(arch)
         return _get_package_mirror_info(availability_zone=availability_zone,
@@ -112,41 +115,109 @@ class Distro(object):
     def _get_localhost_ip(self):
         return "127.0.0.1"
 
+    @abc.abstractmethod
+    def _read_hostname(self, filename, default=None):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def _write_hostname(self, hostname, filename):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def _read_system_hostname(self):
+        raise NotImplementedError()
+
+    def _apply_hostname(self, hostname):
+        # This really only sets the hostname
+        # temporarily (until reboot so it should
+        # not be depended on). Use the write
+        # hostname functions for 'permanent' adjustments.
+        LOG.debug("Non-persistently setting the system hostname to %s",
+                  hostname)
+        try:
+            util.subp(['hostname', hostname])
+        except util.ProcessExecutionError:
+            util.logexc(LOG, ("Failed to non-persistently adjust"
+                              " the system hostname to %s"), hostname)
+
+    @abc.abstractmethod
+    def _select_hostname(self, hostname, fqdn):
+        raise NotImplementedError()
+
+    def update_hostname(self, hostname, fqdn, prev_hostname_fn):
+        applying_hostname = hostname
+        hostname = self._select_hostname(hostname, fqdn)
+        prev_hostname = self._read_hostname(prev_hostname_fn)
+        (sys_fn, sys_hostname) = self._read_system_hostname()
+        update_files = []
+        if not prev_hostname or prev_hostname != hostname:
+            update_files.append(prev_hostname_fn)
+
+        if (not sys_hostname) or (sys_hostname == prev_hostname
+                                  and sys_hostname != hostname):
+            update_files.append(sys_fn)
+
+        update_files = set([f for f in update_files if f])
+        LOG.debug("Attempting to update hostname to %s in %s files",
+                  hostname, len(update_files))
+
+        for fn in update_files:
+            try:
+                self._write_hostname(hostname, fn)
+            except IOError:
+                util.logexc(LOG, "Failed to write hostname %s to %s",
+                            hostname, fn)
+
+        if (sys_hostname and prev_hostname and
+            sys_hostname != prev_hostname):
+            LOG.debug("%s differs from %s, assuming user maintained hostname.",
+                       prev_hostname_fn, sys_fn)
+
+        if sys_fn in update_files:
+            self._apply_hostname(applying_hostname)
+
     def update_etc_hosts(self, hostname, fqdn):
-        # Format defined at
-        # http://unixhelp.ed.ac.uk/CGI/man-cgi?hosts
-        header = "# Added by cloud-init"
-        real_header = "%s on %s" % (header, util.time_rfc2822())
+        header = ''
+        if os.path.exists(self.hosts_fn):
+            eh = hosts.HostsConf(util.load_file(self.hosts_fn))
+        else:
+            eh = hosts.HostsConf('')
+            header = util.make_header(base="added")
         local_ip = self._get_localhost_ip()
-        hosts_line = "%s\t%s %s" % (local_ip, fqdn, hostname)
-        new_etchosts = StringIO()
-        need_write = False
-        need_change = True
-        for line in util.load_file("/etc/hosts").splitlines():
-            if line.strip().startswith(header):
-                continue
-            if not line.strip() or line.strip().startswith("#"):
-                new_etchosts.write("%s\n" % (line))
-                continue
-            split_line = [s.strip() for s in line.split()]
-            if len(split_line) < 2:
-                new_etchosts.write("%s\n" % (line))
-                continue
-            (ip, hosts) = split_line[0], split_line[1:]
-            if ip == local_ip:
-                if sorted([hostname, fqdn]) == sorted(hosts):
-                    need_change = False
-                if need_change:
-                    line = "%s\n%s" % (real_header, hosts_line)
-                    need_change = False
-                    need_write = True
-            new_etchosts.write("%s\n" % (line))
+        prev_info = eh.get_entry(local_ip)
+        need_change = False
+        if not prev_info:
+            eh.add_entry(local_ip, fqdn, hostname)
+            need_change = True
+        else:
+            need_change = True
+            for entry in prev_info:
+                entry_fqdn = None
+                entry_aliases = []
+                if len(entry) >= 1:
+                    entry_fqdn = entry[0]
+                if len(entry) >= 2:
+                    entry_aliases = entry[1:]
+                if entry_fqdn is not None and entry_fqdn == fqdn:
+                    if hostname in entry_aliases:
+                        # Exists already, leave it be
+                        need_change = False
+            if need_change:
+                # Doesn't exist, add that entry in...
+                new_entries = list(prev_info)
+                new_entries.append([fqdn, hostname])
+                eh.del_entries(local_ip)
+                for entry in new_entries:
+                    if len(entry) == 1:
+                        eh.add_entry(local_ip, entry[0])
+                    elif len(entry) >= 2:
+                        eh.add_entry(local_ip, *entry)
         if need_change:
-            new_etchosts.write("%s\n%s\n" % (real_header, hosts_line))
-            need_write = True
-        if need_write:
-            contents = new_etchosts.getvalue()
-            util.write_file("/etc/hosts", contents, mode=0644)
+            contents = StringIO()
+            if header:
+                contents.write("%s\n" % (header))
+            contents.write("%s\n" % (eh))
+            util.write_file(self.hosts_fn, contents.getvalue(), mode=0644)
 
     def _bring_up_interface(self, device_name):
         cmd = ['ifup', device_name]
@@ -305,12 +376,12 @@ class Distro(object):
                 if not base_exists:
                     lines = [('# See sudoers(5) for more information'
                               ' on "#include" directives:'), '',
-                             '# Added by cloud-init',
+                             util.make_header(base="added"),
                              "#includedir %s" % (path), '']
                     sudoers_contents = "\n".join(lines)
                     util.write_file(sudo_base, sudoers_contents, 0440)
                 else:
-                    lines = ['', '# Added by cloud-init',
+                    lines = ['', util.make_header(base="added"),
                              "#includedir %s" % (path), '']
                     sudoers_contents = "\n".join(lines)
                     util.append_file(sudo_base, sudoers_contents)
@@ -322,26 +393,35 @@ class Distro(object):
 
     def write_sudo_rules(self, user, rules, sudo_file=None):
         if not sudo_file:
-            sudo_file = "/etc/sudoers.d/90-cloud-init-users"
+            sudo_file = self.ci_sudoers_fn
 
-        content_header = "# user rules for %s" % user
-        content = "%s\n%s %s\n\n" % (content_header, user, rules)
-
-        if isinstance(rules, list):
-            content = "%s\n" % content_header
+        lines = [
+            '',
+            "# User rules for %s" % user,
+        ]
+        if isinstance(rules, collections.Iterable):
             for rule in rules:
-                content += "%s %s\n" % (user, rule)
-            content += "\n"
+                lines.append("%s %s" % (user, rule))
+        else:
+            lines.append("%s %s" % (user, rules))
+        content = "\n".join(lines)
 
         self.ensure_sudo_dir(os.path.dirname(sudo_file))
-
         if not os.path.exists(sudo_file):
-            util.write_file(sudo_file, content, 0440)
+            contents = [
+                util.make_header(),
+                content,
+            ]
+            try:
+                util.write_file(sudo_file, "\n".join(contents), 0440)
+            except IOError as e:
+                util.logexc(LOG, "Failed to write sudoers file %s", sudo_file)
+                raise e
         else:
             try:
                 util.append_file(sudo_file, content)
             except IOError as e:
-                util.logexc(LOG, "Failed to write %s" % sudo_file, e)
+                util.logexc(LOG, "Failed to append sudoers file %s", sudo_file)
                 raise e
 
     def create_group(self, name, members):
diff --git a/cloudinit/distros/debian.py b/cloudinit/distros/debian.py
index ed4070b4..b6e7654f 100644
--- a/cloudinit/distros/debian.py
+++ b/cloudinit/distros/debian.py
@@ -27,12 +27,20 @@ from cloudinit import helpers
 from cloudinit import log as logging
 from cloudinit import util
 
+from cloudinit.distros.parsers.hostname import HostnameConf
+
 from cloudinit.settings import PER_INSTANCE
 
 LOG = logging.getLogger(__name__)
 
 
 class Distro(distros.Distro):
+    hostname_conf_fn = "/etc/hostname"
+    locale_conf_fn = "/etc/default/locale"
+    network_conf_fn = "/etc/network/interfaces"
+    tz_conf_fn = "/etc/timezone"
+    tz_local_fn = "/etc/localtime"
+    tz_zone_dir = "/usr/share/zoneinfo"
 
     def __init__(self, name, cfg, paths):
         distros.Distro.__init__(self, name, cfg, paths)
@@ -43,10 +51,15 @@ class Distro(distros.Distro):
 
     def apply_locale(self, locale, out_fn=None):
         if not out_fn:
-            out_fn = '/etc/default/locale'
+            out_fn = self.locale_conf_fn
         util.subp(['locale-gen', locale], capture=False)
         util.subp(['update-locale', locale], capture=False)
-        lines = ["# Created by cloud-init", 'LANG="%s"' % (locale), ""]
+        # "" provides trailing newline during join
+        lines = [
+            util.make_header(),
+            'LANG="%s"' % (locale),
+            "",
+        ]
         util.write_file(out_fn, "\n".join(lines))
 
     def install_packages(self, pkglist):
@@ -54,7 +67,7 @@ class Distro(distros.Distro):
         self.package_command('install', pkglist)
 
     def _write_network(self, settings):
-        util.write_file("/etc/network/interfaces", settings)
+        util.write_file(self.network_conf_fn, settings)
         return ['all']
 
     def _bring_up_interfaces(self, device_names):
@@ -67,64 +80,66 @@ class Distro(distros.Distro):
         else:
             return distros.Distro._bring_up_interfaces(self, device_names)
 
-    def set_hostname(self, hostname, fqdn=None):
-        self._write_hostname(hostname, "/etc/hostname")
-        LOG.debug("Setting hostname to %s", hostname)
-        util.subp(['hostname', hostname])
-
-    def _write_hostname(self, hostname, out_fn):
-        # "" gives trailing newline.
-        util.write_file(out_fn, "%s\n" % str(hostname), 0644)
-
-    def update_hostname(self, hostname, fqdn, prev_fn):
-        hostname_prev = self._read_hostname(prev_fn)
-        hostname_in_etc = self._read_hostname("/etc/hostname")
-        update_files = []
-        if not hostname_prev or hostname_prev != hostname:
-            update_files.append(prev_fn)
-        if (not hostname_in_etc or
-            (hostname_in_etc == hostname_prev and
-             hostname_in_etc != hostname)):
-            update_files.append("/etc/hostname")
-        for fn in update_files:
-            try:
-                self._write_hostname(hostname, fn)
-            except:
-                util.logexc(LOG, "Failed to write hostname %s to %s",
-                            hostname, fn)
-        if (hostname_in_etc and hostname_prev and
-            hostname_in_etc != hostname_prev):
-            LOG.debug(("%s differs from /etc/hostname."
-                        " Assuming user maintained hostname."), prev_fn)
-        if "/etc/hostname" in update_files:
-            LOG.debug("Setting hostname to %s", hostname)
-            util.subp(['hostname', hostname])
+    def _select_hostname(self, hostname, fqdn):
+        # Prefer the short hostname over the long
+        # fully qualified domain name
+        if not hostname:
+            return fqdn
+        return hostname
+
+    def _write_hostname(self, your_hostname, out_fn):
+        conf = self._read_hostname_conf(out_fn)
+        if not conf:
+            conf = HostnameConf('')
+            conf.parse()
+        conf.set_hostname(your_hostname)
+        util.write_file(out_fn, str(conf), 0644)
+
+    def _read_system_hostname(self):
+        conf = self._read_hostname_conf(self.hostname_conf_fn)
+        if conf:
+            sys_hostname = conf.hostname
+        else:
+            sys_hostname = None
+        return (self.hostname_conf_fn, sys_hostname)
+
+    def _read_hostname_conf(self, filename):
+        try:
+            conf = HostnameConf(util.load_file(filename))
+            conf.parse()
+            return conf
+        except IOError:
+            util.logexc(LOG, "Error reading hostname from %s", filename)
+            return None
 
     def _read_hostname(self, filename, default=None):
-        contents = util.load_file(filename, quiet=True)
-        for line in contents.splitlines():
-            c_pos = line.find("#")
-            # Handle inline comments
-            if c_pos != -1:
-                line = line[0:c_pos]
-            line_c = line.strip()
-            if line_c:
-                return line_c
-        return default
+        conf = self._read_hostname_conf(filename)
+        if not conf:
+            return default
+        if not conf.hostname:
+            return default
+        return conf.hostname
 
     def _get_localhost_ip(self):
         # Note: http://www.leonardoborda.com/blog/127-0-1-1-ubuntu-debian/
         return "127.0.1.1"
 
     def set_timezone(self, tz):
-        tz_file = os.path.join("/usr/share/zoneinfo", tz)
+        # TODO(harlowja): move this code into
+        # the parent distro...
+        tz_file = os.path.join(self.tz_zone_dir, str(tz))
         if not os.path.isfile(tz_file):
             raise RuntimeError(("Invalid timezone %s,"
                                 " no file found at %s") % (tz, tz_file))
-        # "" provides trailing newline during join
-        tz_lines = ["# Created by cloud-init", str(tz), ""]
-        util.write_file("/etc/timezone", "\n".join(tz_lines))
-        util.copy(tz_file, "/etc/localtime")
+        # Note: "" provides trailing newline during join
+        tz_lines = [
+            util.make_header(),
+            str(tz),
+            "",
+        ]
+        util.write_file(self.tz_conf_fn, "\n".join(tz_lines))
+        # This ensures that the correct tz will be used for the system
+        util.copy(tz_file, self.tz_local_fn)
 
     def package_command(self, command, args=None):
         e = os.environ.copy()
diff --git a/cloudinit/distros/parsers/__init__.py b/cloudinit/distros/parsers/__init__.py
new file mode 100644
index 00000000..1c413eaa
--- /dev/null
+++ b/cloudinit/distros/parsers/__init__.py
@@ -0,0 +1,28 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+def chop_comment(text, comment_chars):
+    comment_locations = [text.find(c) for c in comment_chars]
+    comment_locations = [c for c in comment_locations if c != -1]
+    if not comment_locations:
+        return (text, '')
+    min_comment = min(comment_locations)
+    before_comment = text[0:min_comment]
+    comment = text[min_comment:]
+    return (before_comment, comment)
diff --git a/cloudinit/distros/parsers/hostname.py b/cloudinit/distros/parsers/hostname.py
new file mode 100644
index 00000000..617b3c36
--- /dev/null
+++ b/cloudinit/distros/parsers/hostname.py
@@ -0,0 +1,88 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from StringIO import StringIO
+
+from cloudinit.distros.parsers import chop_comment
+
+
+# Parser that knows how to work with /etc/hostname format
+class HostnameConf(object):
+    def __init__(self, text):
+        self._text = text
+        self._contents = None
+
+    def parse(self):
+        if self._contents is None:
+            self._contents = self._parse(self._text)
+
+    def __str__(self):
+        self.parse()
+        contents = StringIO()
+        for (line_type, components) in self._contents:
+            if line_type == 'blank':
+                contents.write("%s\n" % (components[0]))
+            elif line_type == 'all_comment':
+                contents.write("%s\n" % (components[0]))
+            elif line_type == 'hostname':
+                (hostname, tail) = components
+                contents.write("%s%s\n" % (hostname, tail))
+        # Ensure trailing newline
+        contents = contents.getvalue()
+        if not contents.endswith("\n"):
+            contents += "\n"
+        return contents
+
+    @property
+    def hostname(self):
+        self.parse()
+        for (line_type, components) in self._contents:
+            if line_type == 'hostname':
+                return components[0]
+        return None
+
+    def set_hostname(self, your_hostname):
+        your_hostname = your_hostname.strip()
+        if not your_hostname:
+            return
+        self.parse()
+        replaced = False
+        for (line_type, components) in self._contents:
+            if line_type == 'hostname':
+                components[0] = str(your_hostname)
+                replaced = True
+        if not replaced:
+            self._contents.append(('hostname', [str(your_hostname), '']))
+
+    def _parse(self, contents):
+        entries = []
+        hostnames_found = set()
+        for line in contents.splitlines():
+            if not len(line.strip()):
+                entries.append(('blank', [line]))
+                continue
+            (head, tail) = chop_comment(line.strip(), '#')
+            if not len(head):
+                entries.append(('all_comment', [line]))
+                continue
+            entries.append(('hostname', [head, tail]))
+            hostnames_found.add(head)
+        if len(hostnames_found) > 1:
+            raise IOError("Multiple hostnames (%s) found!"
+                           % (hostnames_found))
+        return entries
diff --git a/cloudinit/distros/parsers/hosts.py b/cloudinit/distros/parsers/hosts.py
new file mode 100644
index 00000000..94c97051
--- /dev/null
+++ b/cloudinit/distros/parsers/hosts.py
@@ -0,0 +1,92 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from StringIO import StringIO
+
+from cloudinit.distros.parsers import chop_comment
+
+
+# See: man hosts
+# or http://unixhelp.ed.ac.uk/CGI/man-cgi?hosts
+# or http://tinyurl.com/6lmox3
+class HostsConf(object):
+    def __init__(self, text):
+        self._text = text
+        self._contents = None
+
+    def parse(self):
+        if self._contents is None:
+            self._contents = self._parse(self._text)
+
+    def get_entry(self, ip):
+        self.parse()
+        options = []
+        for (line_type, components) in self._contents:
+            if line_type == 'option':
+                (pieces, _tail) = components
+                if len(pieces) and pieces[0] == ip:
+                    options.append(pieces[1:])
+        return options
+
+    def del_entries(self, ip):
+        self.parse()
+        n_entries = []
+        for (line_type, components) in self._contents:
+            if line_type != 'option':
+                n_entries.append((line_type, components))
+                continue
+            else:
+                (pieces, _tail) = components
+                if len(pieces) and pieces[0] == ip:
+                    pass
+                elif len(pieces):
+                    n_entries.append((line_type, list(components)))
+        self._contents = n_entries
+
+    def add_entry(self, ip, canonical_hostname, *aliases):
+        self.parse()
+        self._contents.append(('option',
+                              ([ip, canonical_hostname] + list(aliases), '')))
+
+    def _parse(self, contents):
+        entries = []
+        for line in contents.splitlines():
+            if not len(line.strip()):
+                entries.append(('blank', [line]))
+                continue
+            (head, tail) = chop_comment(line.strip(), '#')
+            if not len(head):
+                entries.append(('all_comment', [line]))
+                continue
+            entries.append(('option', [head.split(None), tail]))
+        return entries
+
+    def __str__(self):
+        self.parse()
+        contents = StringIO()
+        for (line_type, components) in self._contents:
+            if line_type == 'blank':
+                contents.write("%s\n" % (components[0]))
+            elif line_type == 'all_comment':
+                contents.write("%s\n" % (components[0]))
+            elif line_type == 'option':
+                (pieces, tail) = components
+                pieces = [str(p) for p in pieces]
+                pieces = "\t".join(pieces)
+                contents.write("%s%s\n" % (pieces, tail))
+        return contents.getvalue()
diff --git a/cloudinit/distros/parsers/resolv_conf.py b/cloudinit/distros/parsers/resolv_conf.py
new file mode 100644
index 00000000..5733c25a
--- /dev/null
+++ b/cloudinit/distros/parsers/resolv_conf.py
@@ -0,0 +1,169 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from StringIO import StringIO
+
+from cloudinit import util
+
+from cloudinit.distros.parsers import chop_comment
+
+
+# See: man resolv.conf
+class ResolvConf(object):
+    def __init__(self, text):
+        self._text = text
+        self._contents = None
+
+    def parse(self):
+        if self._contents is None:
+            self._contents = self._parse(self._text)
+
+    @property
+    def nameservers(self):
+        self.parse()
+        return self._retr_option('nameserver')
+
+    @property
+    def local_domain(self):
+        self.parse()
+        dm = self._retr_option('domain')
+        if dm:
+            return dm[0]
+        return None
+
+    @property
+    def search_domains(self):
+        self.parse()
+        current_sds = self._retr_option('search')
+        flat_sds = []
+        for sdlist in current_sds:
+            for sd in sdlist.split(None):
+                if sd:
+                    flat_sds.append(sd)
+        return flat_sds
+
+    def __str__(self):
+        self.parse()
+        contents = StringIO()
+        for (line_type, components) in self._contents:
+            if line_type == 'blank':
+                contents.write("\n")
+            elif line_type == 'all_comment':
+                contents.write("%s\n" % (components[0]))
+            elif line_type == 'option':
+                (cfg_opt, cfg_value, comment_tail) = components
+                line = "%s %s" % (cfg_opt, cfg_value)
+                if len(comment_tail):
+                    line += comment_tail
+                contents.write("%s\n" % (line))
+        return contents.getvalue()
+
+    def _retr_option(self, opt_name):
+        found = []
+        for (line_type, components) in self._contents:
+            if line_type == 'option':
+                (cfg_opt, cfg_value, _comment_tail) = components
+                if cfg_opt == opt_name:
+                    found.append(cfg_value)
+        return found
+
+    def add_nameserver(self, ns):
+        self.parse()
+        current_ns = self._retr_option('nameserver')
+        new_ns = list(current_ns)
+        new_ns.append(str(ns))
+        new_ns = util.uniq_list(new_ns)
+        if len(new_ns) == len(current_ns):
+            return current_ns
+        if len(current_ns) >= 3:
+            # Hard restriction on only 3 name servers
+            raise ValueError(("Adding %r would go beyond the "
+                              "'3' maximum name servers") % (ns))
+        self._remove_option('nameserver')
+        for n in new_ns:
+            self._contents.append(('option', ['nameserver', n, '']))
+        return new_ns
+
+    def _remove_option(self, opt_name):
+
+        def remove_opt(item):
+            line_type, components = item
+            if line_type != 'option':
+                return False
+            (cfg_opt, _cfg_value, _comment_tail) = components
+            if cfg_opt != opt_name:
+                return False
+            return True
+
+        new_contents = []
+        for c in self._contents:
+            if not remove_opt(c):
+                new_contents.append(c)
+        self._contents = new_contents
+
+    def add_search_domain(self, search_domain):
+        flat_sds = self.search_domains
+        new_sds = list(flat_sds)
+        new_sds.append(str(search_domain))
+        new_sds = util.uniq_list(new_sds)
+        if len(flat_sds) == len(new_sds):
+            return new_sds
+        if len(flat_sds) >= 6:
+            # Hard restriction on only 6 search domains
+            raise ValueError(("Adding %r would go beyond the "
+                              "'6' maximum search domains") % (search_domain))
+        s_list = " ".join(new_sds)
+        if len(s_list) > 256:
+            # Some hard limit on 256 chars total
+            raise ValueError(("Adding %r would go beyond the "
+                              "256 maximum search list character limit")
+                              % (search_domain))
+        self._remove_option('search')
+        self._contents.append(('option', ['search', s_list, '']))
+        return flat_sds
+
+    @local_domain.setter
+    def local_domain(self, domain):
+        self.parse()
+        self._remove_option('domain')
+        self._contents.append(('option', ['domain', str(domain), '']))
+        return domain
+
+    def _parse(self, contents):
+        entries = []
+        for (i, line) in enumerate(contents.splitlines()):
+            sline = line.strip()
+            if not sline:
+                entries.append(('blank', [line]))
+                continue
+            (head, tail) = chop_comment(line, ';#')
+            if not len(head.strip()):
+                entries.append(('all_comment', [line]))
+                continue
+            if not tail:
+                tail = ''
+            try:
+                (cfg_opt, cfg_values) = head.split(None, 1)
+            except (IndexError, ValueError):
+                raise IOError("Incorrectly formatted resolv.conf line %s"
+                              % (i + 1))
+            if cfg_opt not in ['nameserver', 'domain',
+                               'search', 'sortlist', 'options']:
+                raise IOError("Unexpected resolv.conf option %s" % (cfg_opt))
+            entries.append(("option", [cfg_opt, cfg_values, tail]))
+        return entries
diff --git a/cloudinit/distros/parsers/sys_conf.py b/cloudinit/distros/parsers/sys_conf.py
new file mode 100644
index 00000000..20ca1871
--- /dev/null
+++ b/cloudinit/distros/parsers/sys_conf.py
@@ -0,0 +1,113 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from StringIO import StringIO
+
+import pipes
+import re
+
+# This library is used to parse/write
+# out the various sysconfig files edited (best attempt effort)
+#
+# It has to be slightly modified though
+# to ensure that all values are quoted/unquoted correctly
+# since these configs are usually sourced into
+# bash scripts...
+import configobj
+
+# See: http://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap08.html
+# or look at the 'param_expand()' function in the subst.c file in the bash
+# source tarball...
+SHELL_VAR_RULE = r'[a-zA-Z_]+[a-zA-Z0-9_]*'
+SHELL_VAR_REGEXES = [
+    # Basic variables
+    re.compile(r"\$" + SHELL_VAR_RULE),
+    # Things like $?, $0, $-, $@
+    re.compile(r"\$[0-9#\?\-@\*]"),
+    # Things like ${blah:1} - but this one
+    # gets very complex so just try the
+    # simple path
+    re.compile(r"\$\{.+\}"),
+]
+
+
+def _contains_shell_variable(text):
+    for r in SHELL_VAR_REGEXES:
+        if r.search(text):
+            return True
+    return False
+
+
+class SysConf(configobj.ConfigObj):
+    def __init__(self, contents):
+        configobj.ConfigObj.__init__(self, contents,
+                                     interpolation=False,
+                                     write_empty_values=True)
+
+    def __str__(self):
+        contents = self.write()
+        out_contents = StringIO()
+        if isinstance(contents, (list, tuple)):
+            out_contents.write("\n".join(contents))
+        else:
+            out_contents.write(str(contents))
+        return out_contents.getvalue()
+
+    def _quote(self, value, multiline=False):
+        if not isinstance(value, (str, basestring)):
+            raise ValueError('Value "%s" is not a string' % (value))
+        if len(value) == 0:
+            return ''
+        quot_func = None
+        if value[0] in ['"', "'"] and value[-1] in ['"', "'"]:
+            if len(value) == 1:
+                quot_func = (lambda x:
+                                self._get_single_quote(x) % x)
+        else:
+            # Quote whitespace if it isn't the start + end of a shell command
+            if value.strip().startswith("$(") and value.strip().endswith(")"):
+                pass
+            else:
+                if re.search(r"[\t\r\n ]", value):
+                    if _contains_shell_variable(value):
+                        # If it contains shell variables then we likely want to
+                        # leave it alone since the pipes.quote function likes
+                        # to use single quotes which won't get expanded...
+                        if re.search(r"[\n\"']", value):
+                            quot_func = (lambda x:
+                                            self._get_triple_quote(x) % x)
+                        else:
+                            quot_func = (lambda x:
+                                            self._get_single_quote(x) % x)
+                    else:
+                        quot_func = pipes.quote
+        if not quot_func:
+            return value
+        return quot_func(value)
+
+    def _write_line(self, indent_string, entry, this_entry, comment):
+        # Ensure it is formatted fine for
+        # how these sysconfig scripts are used
+        val = self._decode_element(self._quote(this_entry))
+        key = self._decode_element(self._quote(entry))
+        cmnt = self._decode_element(comment)
+        return '%s%s%s%s%s' % (indent_string,
+                               key,
+                               self._a_to_u('='),
+                               val,
+                               cmnt)
diff --git a/cloudinit/distros/rhel.py b/cloudinit/distros/rhel.py
index e4c27216..bc0877d5 100644
--- a/cloudinit/distros/rhel.py
+++ b/cloudinit/distros/rhel.py
@@ -23,39 +23,18 @@
 import os
 
 from cloudinit import distros
+
+from cloudinit.distros.parsers.resolv_conf import ResolvConf
+from cloudinit.distros.parsers.sys_conf import SysConf
+
 from cloudinit import helpers
 from cloudinit import log as logging
 from cloudinit import util
-from cloudinit import version
 
 from cloudinit.settings import PER_INSTANCE
 
 LOG = logging.getLogger(__name__)
 
-NETWORK_FN_TPL = '/etc/sysconfig/network-scripts/ifcfg-%s'
-
-# See: http://tiny.cc/6r99fw
-# For what alot of these files that are being written
-# are and the format of them
-
-# This library is used to parse/write
-# out the various sysconfig files edited
-#
-# It has to be slightly modified though
-# to ensure that all values are quoted
-# since these configs are usually sourced into
-# bash scripts...
-from configobj import ConfigObj
-
-# See: http://tiny.cc/oezbgw
-D_QUOTE_CHARS = {
-    "\"": "\\\"",
-    "(": "\\(",
-    ")": "\\)",
-    "$": '\$',
-    '`': '\`',
-}
-
 
 def _make_sysconfig_bool(val):
     if val:
@@ -64,12 +43,16 @@ def _make_sysconfig_bool(val):
         return 'no'
 
 
-def _make_header():
-    ci_ver = version.version_string()
-    return '# Created by cloud-init v. %s' % (ci_ver)
-
-
 class Distro(distros.Distro):
+    # See: http://tiny.cc/6r99fw
+    clock_conf_fn = "/etc/sysconfig/clock"
+    locale_conf_fn = '/etc/sysconfig/i18n'
+    network_conf_fn = "/etc/sysconfig/network"
+    hostname_conf_fn = "/etc/sysconfig/network"
+    network_script_tpl = '/etc/sysconfig/network-scripts/ifcfg-%s'
+    resolve_conf_fn = "/etc/resolv.conf"
+    tz_local_fn = "/etc/localtime"
+    tz_zone_dir = "/usr/share/zoneinfo"
 
     def __init__(self, name, cfg, paths):
         distros.Distro.__init__(self, name, cfg, paths)
@@ -81,16 +64,29 @@ class Distro(distros.Distro):
     def install_packages(self, pkglist):
         self.package_command('install', pkglist)
 
-    def _write_resolve(self, dns_servers, search_servers):
-        contents = []
+    def _adjust_resolve(self, dns_servers, search_servers):
+        try:
+            r_conf = ResolvConf(util.load_file(self.resolve_conf_fn))
+            r_conf.parse()
+        except IOError:
+            util.logexc(LOG,
+                        "Failed at parsing %s reverting to an empty instance",
+                        self.resolve_conf_fn)
+            r_conf = ResolvConf('')
+            r_conf.parse()
         if dns_servers:
             for s in dns_servers:
-                contents.append("nameserver %s" % (s))
+                try:
+                    r_conf.add_nameserver(s)
+                except ValueError:
+                    util.logexc(LOG, "Failed at adding nameserver %s", s)
         if search_servers:
-            contents.append("search %s" % (" ".join(search_servers)))
-        if contents:
-            contents.insert(0, _make_header())
-            util.write_file("/etc/resolv.conf", "\n".join(contents), 0644)
+            for s in search_servers:
+                try:
+                    r_conf.add_search_domain(s)
+                except ValueError:
+                    util.logexc(LOG, "Failed at adding search domain %s", s)
+        util.write_file(self.resolve_conf_fn, str(r_conf), 0644)
 
     def _write_network(self, settings):
         # TODO(harlowja) fix this... since this is the ubuntu format
@@ -102,7 +98,7 @@ class Distro(distros.Distro):
         searchservers = []
         dev_names = entries.keys()
         for (dev, info) in entries.iteritems():
-            net_fn = NETWORK_FN_TPL % (dev)
+            net_fn = self.network_script_tpl % (dev)
             net_cfg = {
                 'DEVICE': dev,
                 'NETMASK': info.get('netmask'),
@@ -119,12 +115,12 @@ class Distro(distros.Distro):
             if 'dns-search' in info:
                 searchservers.extend(info['dns-search'])
         if nameservers or searchservers:
-            self._write_resolve(nameservers, searchservers)
+            self._adjust_resolve(nameservers, searchservers)
         if dev_names:
             net_cfg = {
                 'NETWORKING': _make_sysconfig_bool(True),
             }
-            self._update_sysconfig_file("/etc/sysconfig/network", net_cfg)
+            self._update_sysconfig_file(self.network_conf_fn, net_cfg)
         return dev_names
 
     def _update_sysconfig_file(self, fn, adjustments, allow_empty=False):
@@ -141,24 +137,16 @@ class Distro(distros.Distro):
             contents[k] = v
             updated_am += 1
         if updated_am:
-            lines = contents.write()
+            lines = [
+                str(contents),
+            ]
             if not exists:
-                lines.insert(0, _make_header())
+                lines.insert(0, util.make_header())
             util.write_file(fn, "\n".join(lines), 0644)
 
-    def set_hostname(self, hostname, fqdn=None):
-        # See: http://bit.ly/TwitgL
-        # Should be fqdn if we can use it
-        sysconfig_hostname = fqdn
-        if not sysconfig_hostname:
-            sysconfig_hostname = hostname
-        self._write_hostname(sysconfig_hostname, '/etc/sysconfig/network')
-        LOG.debug("Setting hostname to %s", hostname)
-        util.subp(['hostname', hostname])
-
     def apply_locale(self, locale, out_fn=None):
         if not out_fn:
-            out_fn = '/etc/sysconfig/i18n'
+            out_fn = self.locale_conf_fn
         locale_cfg = {
             'LANG': locale,
         }
@@ -170,34 +158,16 @@ class Distro(distros.Distro):
         }
         self._update_sysconfig_file(out_fn, host_cfg)
 
-    def update_hostname(self, hostname, fqdn, prev_file):
+    def _select_hostname(self, hostname, fqdn):
         # See: http://bit.ly/TwitgL
         # Should be fqdn if we can use it
-        sysconfig_hostname = fqdn
-        if not sysconfig_hostname:
-            sysconfig_hostname = hostname
-        hostname_prev = self._read_hostname(prev_file)
-        hostname_in_sys = self._read_hostname("/etc/sysconfig/network")
-        update_files = []
-        if not hostname_prev or hostname_prev != sysconfig_hostname:
-            update_files.append(prev_file)
-        if (not hostname_in_sys or
-            (hostname_in_sys == hostname_prev
-             and hostname_in_sys != sysconfig_hostname)):
-            update_files.append("/etc/sysconfig/network")
-        for fn in update_files:
-            try:
-                self._write_hostname(sysconfig_hostname, fn)
-            except:
-                util.logexc(LOG, "Failed to write hostname %s to %s",
-                            sysconfig_hostname, fn)
-        if (hostname_in_sys and hostname_prev and
-            hostname_in_sys != hostname_prev):
-            LOG.debug(("%s differs from /etc/sysconfig/network."
-                        " Assuming user maintained hostname."), prev_file)
-        if "/etc/sysconfig/network" in update_files:
-            LOG.debug("Setting hostname to %s", hostname)
-            util.subp(['hostname', hostname])
+        if fqdn:
+            return fqdn
+        return hostname
+
+    def _read_system_hostname(self):
+        return (self.network_conf_fn,
+                self._read_hostname(self.network_conf_fn))
 
     def _read_hostname(self, filename, default=None):
         (_exists, contents) = self._read_conf(filename)
@@ -208,12 +178,13 @@ class Distro(distros.Distro):
 
     def _read_conf(self, fn):
         exists = False
-        if os.path.isfile(fn):
+        try:
             contents = util.load_file(fn).splitlines()
             exists = True
-        else:
+        except IOError:
             contents = []
-        return (exists, QuotingConfigObj(contents))
+        return (exists,
+                SysConf(contents))
 
     def _bring_up_interfaces(self, device_names):
         if device_names and 'all' in device_names:
@@ -222,17 +193,19 @@ class Distro(distros.Distro):
         return distros.Distro._bring_up_interfaces(self, device_names)
 
     def set_timezone(self, tz):
-        tz_file = os.path.join("/usr/share/zoneinfo", tz)
+        # TODO(harlowja): move this code into
+        # the parent distro...
+        tz_file = os.path.join(self.tz_zone_dir, str(tz))
         if not os.path.isfile(tz_file):
             raise RuntimeError(("Invalid timezone %s,"
                                 " no file found at %s") % (tz, tz_file))
         # Adjust the sysconfig clock zone setting
         clock_cfg = {
-            'ZONE': tz,
+            'ZONE': str(tz),
         }
-        self._update_sysconfig_file("/etc/sysconfig/clock", clock_cfg)
+        self._update_sysconfig_file(self.clock_conf_fn, clock_cfg)
         # This ensures that the correct tz will be used for the system
-        util.copy(tz_file, "/etc/localtime")
+        util.copy(tz_file, self.tz_local_fn)
 
     def package_command(self, command, args=None):
         cmd = ['yum']
@@ -256,51 +229,6 @@ class Distro(distros.Distro):
                          ["makecache"], freq=PER_INSTANCE)
 
 
-# This class helps adjust the configobj
-# writing to ensure that when writing a k/v
-# on a line, that they are properly quoted
-# and have no spaces between the '=' sign.
-# - This is mainly due to the fact that
-# the sysconfig scripts are often sourced
-# directly into bash/shell scripts so ensure
-# that it works for those types of use cases.
-class QuotingConfigObj(ConfigObj):
-    def __init__(self, lines):
-        ConfigObj.__init__(self, lines,
-                           interpolation=False,
-                           write_empty_values=True)
-
-    def _quote_posix(self, text):
-        if not text:
-            return ''
-        for (k, v) in D_QUOTE_CHARS.iteritems():
-            text = text.replace(k, v)
-        return '"%s"' % (text)
-
-    def _quote_special(self, text):
-        if text.lower() in ['yes', 'no', 'true', 'false']:
-            return text
-        else:
-            return self._quote_posix(text)
-
-    def _write_line(self, indent_string, entry, this_entry, comment):
-        # Ensure it is formatted fine for
-        # how these sysconfig scripts are used
-        val = self._decode_element(self._quote(this_entry))
-        # Single quoted strings should
-        # always work.
-        if not val.startswith("'"):
-            # Perform any special quoting
-            val = self._quote_special(val)
-        key = self._decode_element(self._quote(entry, multiline=False))
-        cmnt = self._decode_element(comment)
-        return '%s%s%s%s%s' % (indent_string,
-                               key,
-                               "=",
-                               val,
-                               cmnt)
-
-
 # This is a util function to translate a ubuntu /etc/network/interfaces 'blob'
 # to a rhel equiv. that can then be written to /etc/sysconfig/network-scripts/
 # TODO(harlowja) remove when we have python-netcf active...
diff --git a/cloudinit/util.py b/cloudinit/util.py
index 4f5b15ee..ab918433 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -52,6 +52,7 @@ from cloudinit import importer
 from cloudinit import log as logging
 from cloudinit import safeyaml
 from cloudinit import url_helper as uhelp
+from cloudinit import version
 
 from cloudinit.settings import (CFG_BUILTIN)
 
@@ -272,11 +273,7 @@ def uniq_merge(*lists):
             # Kickout the empty ones
             a_list = [a for a in a_list if len(a)]
         combined_list.extend(a_list)
-    uniq_list = []
-    for i in combined_list:
-        if i not in uniq_list:
-            uniq_list.append(i)
-    return uniq_list
+    return uniq_list(combined_list)
 
 
 def clean_filename(fn):
@@ -989,6 +986,16 @@ def peek_file(fname, max_bytes):
         return ifh.read(max_bytes)
 
 
+def uniq_list(in_list):
+    out_list = []
+    for i in in_list:
+        if i in out_list:
+            continue
+        else:
+            out_list.append(i)
+    return out_list
+
+
 def load_file(fname, read_cb=None, quiet=False):
     LOG.debug("Reading from %s (quiet=%s)", fname, quiet)
     ofh = StringIO()
@@ -1428,6 +1435,14 @@ def subp(args, data=None, rcs=None, env=None, capture=True, shell=False,
     return (out, err)
 
 
+def make_header(comment_char="#", base='created'):
+    ci_ver = version.version_string()
+    header = str(comment_char)
+    header += " %s by cloud-init v. %s" % (base.title(), ci_ver)
+    header += " on %s" % time_rfc2822()
+    return header
+
+
 def abs_join(*paths):
     return os.path.abspath(os.path.join(*paths))