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Edit File: unattended-upgrade

#!/usr/bin/python3
# Copyright (c) 2005-2015 Canonical Ltd
#
# AUTHOR:
# Michael Vogt <mvo@ubuntu.com>
#
# This file is part of unattended-upgrades
#
# unattended-upgrades is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as published
# by the Free Software Foundation; either version 2 of the License, or (at
# your option) any later version.
#
# unattended-upgrades 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 unattended-upgrades; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#

import copy
import datetime
import errno
import email.charset
import fcntl
import fnmatch
import gettext
import grp
import io
import locale
import logging
import logging.handlers
import re
import os
import select
import signal
import string
import subprocess
import sys

from datetime import date
from email.message import Message
from gettext import gettext as _
from io import StringIO
from optparse import (
    OptionParser,
    SUPPRESS_HELP,
)

from subprocess import (
    Popen,
    PIPE,
)
import apt
import apt_inst
import apt_pkg

# the reboot required flag file used by packages
REBOOT_REQUIRED_FILE = "/var/run/reboot-required"
MAIL_BINARY = "/usr/bin/mail"
SENDMAIL_BINARY = "/usr/sbin/sendmail"
USERS = "/usr/bin/users"
# no py3 lsb_release in debian :/
DISTRO_CODENAME = subprocess.check_output(
    ["lsb_release", "-c", "-s"], universal_newlines=True).strip()
DISTRO_ID = subprocess.check_output(
    ["lsb_release", "-i", "-s"], universal_newlines=True).strip()

# progress information is written here
PROGRESS_LOG = "/var/run/unattended-upgrades.progress"
PID_FILE = "/var/run/unattended-upgrades.pid"

# set from the sigint signal handler
SIGNAL_STOP_REQUEST = False

class LoggingDateTime:
    """The date/time representation for the dpkg log file timestamps"""
    LOG_DATE_TIME_FMT = "%Y-%m-%d  %H:%M:%S"

@classmethod
    def as_string(cls):
        """Return the current date and time as LOG_DATE_TIME_FMT string"""
        return datetime.datetime.now().strftime(cls.LOG_DATE_TIME_FMT)

@classmethod
    def from_string(cls, logstr):
        """Take a LOG_DATE_TIME_FMT string and return datetime object"""
        return datetime.datetime.strptime(logstr, cls.LOG_DATE_TIME_FMT)

class UnknownMatcherError(ValueError):
    pass

class UnattendedUpgradesCache(apt.Cache):

def __init__(self, rootdir, allowed_origins):
        apt.Cache.__init__(self, rootdir=rootdir)
        self.allowed_origins = allowed_origins
        # ensure we update the candidate versions
        self.adjust_candidate_versions()

def clear(self):
        apt.Cache.clear(self)
        # ensure we update the candidate versions
        self.adjust_candidate_versions()

def adjust_candidate_versions(self):
        """ Adjust candidate versions to match highest allowed origin

This adjusts the origin even if the candidate has a higher
            version. This is needed when e.g. a package is available in
            the security pocket but there is also a package in the
            updates pocket with a higher version number
        """
        for pkg in self:
            # important! this avoids downgrades below
            if not pkg.is_upgradable:
                continue
            # check if the candidate is already pointing to a allowed
            # origin and if so, do not mess with it
            if is_allowed_origin(pkg.candidate, self.allowed_origins):
                continue
            # check if we have a version in a allowed origin that is
            # not the candidate
            new_cand = None
            for ver in pkg.versions:
                # ignore versions that the user marked with priority < 100
                # (and ensure we have a python-apt that supports this)
                if (hasattr(ver, "policy_priority") and
                        ver.policy_priority < 100):
                    logging.debug("ignoring ver '%s' with priority < 0" % ver)
                    continue
                if is_allowed_origin(ver, self.allowed_origins):
                    # leave as soon as we have the highest new candidate
                    new_cand = ver
                    break
            if new_cand and new_cand != pkg.candidate:
                logging.debug("adjusting candidate version: '%s'" % new_cand)
                pkg.candidate = new_cand

class LogInstallProgress(apt.progress.base.InstallProgress):
    """ Install progress that writes to self.progress_log
        (/var/run/unattended-upgrades.progress by default)
    """

def __init__(self, logfile_dpkg, verbose=False,
                 progress_log="var/run/unattended-upgrades.progress"):
        apt.progress.base.InstallProgress.__init__(self)
        self.logfile_dpkg = logfile_dpkg
        self.progress_log = os.path.join(apt_pkg.config.find_dir("Dir"),
                                         progress_log)
        self.verbose = verbose
        self.output_logfd = None

def status_change(self, pkg, percent, status):
        with open(self.progress_log, "w") as f:
            f.write(_("Progress: %s %% (%s)") % (percent, pkg))

def _fixup_fds(self):
        required_fds = [0, 1, 2,  # stdin, stdout, stderr
                        self.writefd,
                        self.write_stream.fileno(),
                        self.statusfd,
                        self.status_stream.fileno()
                        ]
        # ensure that our required fds close on exec
        for fd in required_fds[3:]:
            old_flags = fcntl.fcntl(fd, fcntl.F_GETFD)
            fcntl.fcntl(fd, fcntl.F_SETFD, old_flags | fcntl.FD_CLOEXEC)
        # close all fds
        proc_fd = "/proc/self/fd"
        if os.path.exists(proc_fd):
            error_count = 0
            for fdname in os.listdir(proc_fd):
                try:
                    fd = int(fdname)
                except Exception as e:
                    print("ERROR: can not get fd for '%s'" % fdname)
                if fd in required_fds:
                    continue
                try:
                    os.close(fd)
                    # print("closed: ", fd)
                except OSError as e:
                    # there will be one fd that can not be closed
                    # as its the fd from pythons internal diropen()
                    # so its ok to ignore one close error
                    error_count += 1
                    if error_count > 1:
                        print("ERROR: os.close(%s): %s" % (fd, e))

def _redirect_stdin(self):
        REDIRECT_INPUT = os.devnull
        fd = os.open(REDIRECT_INPUT, os.O_RDWR)
        os.dup2(fd, 0)

def _redirect_output(self):
        # do not create log in dry-run mode, just output to stdout/stderr
        if not apt_pkg.config.find_b("Debug::pkgDPkgPM", False):
            logfd = self._get_logfile_dpkg_fd()
            os.dup2(logfd, 1)
            os.dup2(logfd, 2)

def _get_logfile_dpkg_fd(self):
        logfd = os.open(
            self.logfile_dpkg, os.O_RDWR | os.O_APPEND | os.O_CREAT, 0o640)
        try:
            adm_gid = grp.getgrnam("adm").gr_gid
            os.fchown(logfd, 0, adm_gid)
        except (KeyError, OSError):
            pass
        return logfd

def update_interface(self):
        # call super class first
        apt.progress.base.InstallProgress.update_interface(self)
        self._do_verbose_output_if_needed()

def _do_verbose_output_if_needed(self):
        # if we are in debug mode, nothing to be more verbose about
        if apt_pkg.config.find_b("Debug::pkgDPkgPM", False):
            return
        # handle verbose
        if self.verbose:
            if self.output_logfd is None:
                self.output_logfd = os.open(self.logfile_dpkg, os.O_RDONLY)
                os.lseek(self.output_logfd, 0, os.SEEK_END)
            try:
                select.select([self.output_logfd], [], [], 0)
            except select.error as e:
                if e.errno != errno.EINTR:
                    logging.exception("select failed")
            # output to stdout in verbose mode only
            os.write(1, os.read(self.output_logfd, 1024))

def _log_in_dpkg_log(self, msg):
        logfd = self._get_logfile_dpkg_fd()
        os.write(logfd, msg.encode("utf-8"))
        os.close(logfd)

def finish_update(self):
        self._log_in_dpkg_log("Log ended: %s\n\n"
                              % LoggingDateTime.as_string())

def fork(self):
        self._log_in_dpkg_log("Log started: %s\n"
                              % LoggingDateTime.as_string())
        pid = os.fork()
        if pid == 0:
            self._fixup_fds()
            self._redirect_stdin()
            self._redirect_output()
        return pid

class Unlocked:
    """
    Context manager for unlocking the apt lock while cache.commit() is run
    """

def __enter__(self):
        try:
            apt_pkg.pkgsystem_unlock()
        except:
            pass

def __exit__(self, exc_type, exc_value, exc_tb):
        try:
            apt_pkg.pkgsystem_unlock()
        except:
            pass

def is_dpkg_journal_dirty():
    """
    Return True if the dpkg journal is dirty
    (similar to debSystem::CheckUpdates)
    """
    d = os.path.join(
        os.path.dirname(apt_pkg.config.find_file("Dir::State::status")),
        "updates")
    for f in os.listdir(d):
        if re.match("[0-9]+", f):
            return True
    return False

def signal_handler(signal, frame):
    logging.warning("SIGUSR1 received, will stop")
    global SIGNAL_STOP_REQUEST
    SIGNAL_STOP_REQUEST = True

def substitute(line):
    """ substitude known mappings and return a new string

Currently supported ${distro-release}
    """
    mapping = {"distro_codename": get_distro_codename(),
               "distro_id": get_distro_id()}
    return string.Template(line).substitute(mapping)

def get_distro_codename():
    return DISTRO_CODENAME

def get_distro_id():
    return DISTRO_ID

def get_allowed_origins_legacy():
    """ legacy support for old Allowed-Origins var """
    allowed_origins = []
    for s in apt_pkg.config.value_list("Unattended-Upgrade::Allowed-Origins"):
        # if there is a ":" use that as seperator, else use spaces
        if re.findall(r'(?<!\\):', s):
            (distro_id, distro_codename) = re.split(r'(?<!\\):', s)
        else:
            (distro_id, distro_codename) = s.split()
        # unescape "\:" back to ":"
        distro_id = re.sub(r'\\:', ':', distro_id)
        # escape "," (see LP: #824856) - i wonder if there is a simpler way?
        distro_id = re.sub(r'([^\\]),', r'\1\\,', distro_id)
        distro_codename = re.sub(r'([^\\]),', r'\1\\,', distro_codename)
        # convert to new format
        allowed_origins.append("o=%s,a=%s" % (substitute(distro_id),
                                              substitute(distro_codename)))
    return allowed_origins

def get_allowed_origins():
    """ return a list of allowed origins from apt.conf

This will take substitutions (like distro_id) into account.
    """
    allowed_origins = get_allowed_origins_legacy()
    for s in apt_pkg.config.value_list("Unattended-Upgrade::Origins-Pattern"):
        allowed_origins.append(substitute(s))
    return allowed_origins

def match_whitelist_string(whitelist, origin):
    """
    take a whitelist string in the form "origin=Debian,label=Debian-Security"
    and match against the given python-apt origin. A empty whitelist string
    never matches anything.
    """
    whitelist = whitelist.strip()
    if whitelist == "":
        logging.warning("empty match string matches nothing")
        return False
    res = True
    # make "\," the html quote equivalent
    whitelist = whitelist.replace("\,", "%2C")
    for token in whitelist.split(","):
        # strip and unquote the "," back
        (what, value) = [s.strip().replace("%2C", ",")
                         for s in token.split("=")]
        # logging.debug("matching '%s'='%s' against '%s'" % (
        #              what, value, origin))
        # support substitution here as well
        value = substitute(value)
        # first char is apt-cache policy output, send is the name
        # in the Release file
        if what in ("o", "origin"):
            res &= fnmatch.fnmatch(origin.origin, value)
        elif what in ("l", "label"):
            res &= fnmatch.fnmatch(origin.label, value)
        elif what in ("a", "suite", "archive"):
            res &= fnmatch.fnmatch(origin.archive, value)
        elif what in ("c", "component"):
            res &= fnmatch.fnmatch(origin.component, value)
        elif what in ("site",):
            res &= fnmatch.fnmatch(origin.site, value)
        elif what in ("n", "codename",):
            res &= fnmatch.fnmatch(origin.codename, value)
        else:
            raise UnknownMatcherError(
                "Unknown whitelist entry for macher '%s' (token '%s')" % (
                    what, token))
        # logging.debug("matching '%s'='%s' against '%s'" % (
        #              what, value, origin))
    return res

def cache_commit(cache, logfile_dpkg, verbose, iprogress=None):
    """Commit the changes from the given cache to the system"""
    # set debconf to NON_INTERACTIVE, redirect output
    os.putenv("DEBIAN_FRONTEND", "noninteractive")

# only act if there is anything to do (important to avoid writing
    # empty log stanzas)
    if len(cache.get_changes()) == 0:
        return True, None

error = None
    res = False
    if iprogress is None:
        iprogress = LogInstallProgress(logfile_dpkg, verbose)

try:
        with Unlocked():
            res = cache.commit(install_progress=iprogress)
    except SystemError as e:
        error = e
        if verbose:
            logging.exception("Exception happened during upgrade.")
    return res, error

def upgrade_normal(cache, logfile_dpkg, verbose):
    res, error = cache_commit(cache, logfile_dpkg, verbose)
    if res:
        logging.info(_("All upgrades installed"))
    else:
        logging.error(_("Installing the upgrades failed!"))
        logging.error(_("error message: '%s'"), error)
        logging.error(_("dpkg returned a error! See '%s' for details"),
                      logfile_dpkg)
    return res

def upgrade_in_minimal_steps(cache, pkgs_to_upgrade, blacklist,
                             whitelist, logfile_dpkg="", verbose=False):

install_log = LogInstallProgress(logfile_dpkg, verbose)
    install_log.progress_log += ".minimal-steps"

# setup signal handler
    signal.signal(signal.SIGUSR1, signal_handler)

# double check any changes we do
    allowed_origins = get_allowed_origins()

# to upgrade contains the package names
    to_upgrade = set(pkgs_to_upgrade)
    while True:
        # find smallest set
        smallest_partition = set()
        for pkgname in to_upgrade:
            if SIGNAL_STOP_REQUEST:
                logging.warning("SIGNAL received, stopping")
                return True
            pkg = cache[pkgname]
            if pkg.is_upgradable:
                pkg.mark_upgrade(from_user=not pkg.is_auto_installed)
            elif not pkg.is_installed:
                pkg.mark_install(from_user=False)
            else:
                continue
            # double check that we are not running into side effects like
            # what could have been caused LP: #1020680
            if not check_changes_for_sanity(cache, allowed_origins, blacklist,
                                            whitelist):
                logging.info("While building minimal partition: "
                             "cache has not allowed changes")
                cache.clear()
                continue
            changes = [p.name for p in cache.get_changes()]
            if not changes:
                continue
            if len(changes) == 1:
                logging.debug("found leaf package %s" % pkg.name)
                smallest_partition = changes
                break
            if (len(changes) < len(smallest_partition) or
                    len(smallest_partition) == 0):
                logging.debug("found partition of size %s (%s)" % (
                    len(changes), changes))
                smallest_partition = changes
            cache.clear()

if len(smallest_partition) == 0:
            logging.info(
                _("Some packages can not be upgraded: %s") % (to_upgrade))
            break

# write progress log information
        if len(pkgs_to_upgrade) > 0:
            percent = ((len(pkgs_to_upgrade) - len(to_upgrade)) /
                       float(len(pkgs_to_upgrade)) * 100.0)
        else:
            percent = 100.0
        install_log.status_change(pkg=",".join(smallest_partition),
                                  percent=percent,
                                  status="")
        # apply changes
        logging.debug("applying set %s" % smallest_partition)
        rewind_cache(cache, [cache[name] for name in smallest_partition])

# one last check, just to be sure
        if not check_changes_for_sanity(cache, allowed_origins, blacklist,
                                        whitelist):
            logging.error("Failed sanity check while attempting to commit: "
                          "this should never happen")
            cache.clear()
            return False

res, error = cache_commit(cache, logfile_dpkg, verbose, install_log)
        if error:
            if verbose:
                logging.exception("Exception happened during upgrade.")
            logging.error(_("Installing the upgrades failed!"))
            logging.error(_("error message: '%s'"), error)
            logging.error(_("dpkg returned a error! See '%s' for details"),
                          logfile_dpkg)
            return False
        to_upgrade = to_upgrade - set(smallest_partition)
        logging.debug("left to upgrade %s" % to_upgrade)
        if len(to_upgrade) == 0:
            logging.info(_("All upgrades installed"))
            break
    return True

def is_allowed_origin(ver, allowed_origins):
    if not ver:
        return False
    for origin in ver.origins:
        for allowed in allowed_origins:
            if match_whitelist_string(allowed, origin):
                return True
    return False

def is_pkgname_in_blacklist(pkgname, blacklist):
    for blacklist_regexp in blacklist:
        if re.match(blacklist_regexp, pkgname):
            logging.debug("skipping blacklisted package '%s'" % pkgname)
            return True
    return False

def is_pkgname_in_whitelist(pkgname, whitelist):
    # a empty whitelist means the user does not want to use this feature
    if not whitelist:
        return True
    for whitelist_regexp in whitelist:
        if re.match(whitelist_regexp, pkgname):
            logging.debug("only upgrading the following package '%s'" %
                          pkgname)
            return True
    return False

def check_changes_for_sanity(cache, allowed_origins, blacklist, whitelist):
    if cache._depcache.broken_count != 0:
        return False
    for pkg in cache:
        if pkg.marked_delete:
            logging.debug("pkg '%s' now marked delete" % pkg.name)
            return False
        if pkg.marked_install or pkg.marked_upgrade:
            # apt will never fallback from a trusted to a untrusted
            # origin so its good enough if we have a single trusted one
            if not any([o.trusted for o in pkg.candidate.origins]):
                logging.debug("pkg '%s' is untrusted" % pkg.name)
                return False
            if not is_allowed_origin(pkg.candidate, allowed_origins):
                logging.debug("pkg '%s' not in allowed origin" % pkg.name)
                return False
            if is_pkgname_in_blacklist(pkg.name, blacklist):
                logging.debug("pkg '%s' package has been blacklisted" %
                              pkg.name)
                return False
            # a strict whitelist will not allow any changes not in the
            # whitelist, most people will want the relaxed whitelist
            # that whitelists a package but pulls in the package
            # dependencies
            strict_whitelist = apt_pkg.config.find_b(
                "Unattended-Upgrade::Package-Whitelist-Strict", False)
            if (strict_whitelist and
                    not is_pkgname_in_whitelist(pkg.name, whitelist)):

logging.debug("pkg '%s' package is not whitelisted" %
                              pkg.name)
                return False
            if pkg._pkg.selected_state == apt_pkg.SELSTATE_HOLD:
                logging.debug("pkg '%s' is on hold" % pkg.name)
                return False
            # check if the package is unsafe to upgrade unattended
            ignore_require_restart = apt_pkg.config.find_b(
                "Unattended-Upgrade::IgnoreAppsRequireRestart", False)
            upgrade_requires = pkg.candidate.record.get("Upgrade-Requires")
            if (pkg.marked_upgrade and ignore_require_restart is False and
                    upgrade_requires == "app-restart"):
                logging.debug("pkg '%s' requires app-restart, not safe to "
                              "upgrade unattended")
                return False
    return True

def pkgname_from_deb(debfile):
    # FIXME: add error checking here
    try:
        control = apt_inst.DebFile(debfile).control.extractdata("control")
        sections = apt_pkg.TagSection(control)
        return sections["Package"]
    except (IOError, SystemError) as e:
        logging.error("failed to read deb file '%s' (%s)" % (debfile, e))
        # dumb fallback
        return debfile.split("_")[0]

def get_md5sum_for_file_in_deb(deb_file, conf_file):
    dpkg_cmd = ["dpkg-deb", "--fsys-tarfile", deb_file]
    tar_cmd = ["tar", "-x", "-O", "-f", "-", "." + conf_file]
    md5_cmd = ["md5sum"]
    dpkg_p = Popen(dpkg_cmd, stdout=PIPE)
    tar_p = Popen(tar_cmd, stdin=dpkg_p.stdout, stdout=PIPE,
                  universal_newlines=True)
    md5_p = Popen(md5_cmd, stdin=tar_p.stdout, stdout=PIPE,
                  universal_newlines=True)
    pkg_md5sum = md5_p.communicate()[0].split()[0]
    return pkg_md5sum

# prefix is *only* needed for the build-in tests
def conffile_prompt(destFile, prefix=""):
    logging.debug("check_conffile_prompt('%s')" % destFile)
    pkgname = pkgname_from_deb(destFile)

# get the conffiles for the /var/lib/dpkg/status file
    status_file = apt_pkg.config.find("Dir::State::status")
    tagfile = apt_pkg.TagFile(open(status_file, "r"))
    conffiles = ""
    for section in tagfile:
        if section.get("Package") == pkgname:
            logging.debug("found pkg: %s" % pkgname)
            if "Conffiles" in section:
                conffiles = section.get("Conffiles")
                break

# get conffile value from pkg, its ok if the new version
    # does not have conffiles anymore
    pkg_conffiles = ""
    deb = apt_inst.DebFile(destFile)
    try:
        pkg_conffiles = deb.control.extractdata("conffiles").strip().decode(
            "utf-8")
    except LookupError as e:
        logging.debug("No conffiles in deb '%s' (%s)" % (destFile, e))

# Conffiles:
    #  /etc/bash_completion.d/m-a c7780fab6b14d75ca54e11e992a6c11c
    dpkg_status_conffiles = {}
    for line in conffiles.splitlines():
        # ignore empty lines
        line = line.strip()
        if not line:
            continue
        # show what we do
        logging.debug("conffile line: '%s'", line)
        li = line.split()
        conf_file = li[0]
        md5 = li[1]
        if len(li) > 2:
            obs = li[2]
        else:
            obs = None
        # ignore if conffile is obsolete
        if obs == "obsolete":
            continue
        # ignore state "newconffile" until its clearer if there
        # might be a dpkg prompt (LP: #936870)
        if md5 == "newconffile":
            continue
        if not pkg_conffiles or conf_file not in pkg_conffiles.split("\n"):
            logging.debug("'%s' not in package conffiles '%s'" % (
                conf_file, pkg_conffiles))
            continue
        # record for later
        dpkg_status_conffiles[conf_file] = md5

# test against the installed file, if the local file got deleted
        # by the admin thats ok but it may still trigger a conffile prompt
        # (see debian #788049)
        current_md5 = ""
        if os.path.exists(prefix + conf_file):
            with open(prefix + conf_file, 'rb') as fb:
                current_md5 = apt_pkg.md5sum(fb)
        logging.debug("current md5: %s" % current_md5)

# hashes are the same, no conffile prompt
        if current_md5 == md5:
            continue
        # calculate md5sum from the deb (may take a bit)
        pkg_md5sum = get_md5sum_for_file_in_deb(destFile, conf_file)
        logging.debug("pkg_md5sum: %s" % pkg_md5sum)
        # the md5sum in the deb is unchanged, this will not
        # trigger a conffile prompt
        if pkg_md5sum == md5:
            continue
        # if we made it to this point:
        #  current_md5 != pkg_md5sum != md5
        # and that will trigger a conffile prompt, we can
        # stop processing at this point and just return True
        return True

# now check if there are conffiles in the pkg that where not there
    # in the previous version in the dpkg status file
    if pkg_conffiles:
        for conf_file in pkg_conffiles.split("\n"):
            if (conf_file not in dpkg_status_conffiles and
                    os.path.exists(prefix + conf_file)):
                logging.debug("found conffile '%s' in new pkg but on dpkg "
                              "status" % conf_file)
                pkg_md5sum = get_md5sum_for_file_in_deb(destFile, conf_file)
                with open(prefix + conf_file, 'rb') as fp:
                    if pkg_md5sum != apt_pkg.md5sum(fp):
                        return True
    return False

def dpkg_conffile_prompt():
    if "DPkg::Options" not in apt_pkg.config:
        return True
    options = apt_pkg.config.value_list("DPkg::Options")
    for option in options:
        option = option.strip()
        if option in ["--force-confold", "--force-confnew"]:
            return False
    return True

def rewind_cache(cache, pkgs_to_upgrade):
    """ set the cache back to the state with packages_to_upgrade """
    cache.clear()
    for pkg2 in pkgs_to_upgrade:
        pkg2.mark_install(from_user=not pkg2.is_auto_installed)
    if cache.broken_count > 0:
        raise AssertionError("rewind_cache created a broken cache")

def host():
    return os.uname()[1]

# *sigh* textwrap is nice, but it breaks "linux-image" into two
# seperate lines
def wrap(t, width=70, subsequent_indent=""):
    out = ""
    for s in t.split():
        if (len(out) - out.rfind("\n")) + len(s) > width:
            out += "\n" + subsequent_indent
        out += s + " "
    return out

def setup_apt_listchanges(conf="/etc/apt/listchanges.conf"):
    """ deal with apt-listchanges """
    # apt-listchanges will always send a mail if there is a mail address
    # set in the config regardless of the frontend used, so set it to
    # mail if we have a sendmail and to none if not (as it appears to
    # not check if sendmail is there or not), debian bug #579733
    if os.path.exists(SENDMAIL_BINARY):
        os.environ["APT_LISTCHANGES_FRONTEND"] = "mail"
    else:
        os.environ["APT_LISTCHANGES_FRONTEND"] = "none"

def _send_mail_using_mailx(from_address, to_address, subject, body):
    # ensure that the body is a byte stream and that we do not
    # break on encoding errors (the default error mode is "strict")
    encoded_body = body.encode(
        locale.getpreferredencoding(False), errors="replace")
    # we use a binary pipe to stdin to ensure we do not break on
    # unicode encoding errors (e.g. because the user is running a
    # ascii only system like the buildds)
    mail = subprocess.Popen(
        [MAIL_BINARY, "-r", from_address, "-s", subject, to_address],
        stdin=subprocess.PIPE, universal_newlines=False)
    mail.stdin.write(encoded_body)
    mail.stdin.close()
    ret = mail.wait()
    return ret

def _send_mail_using_sendmail(from_address, to_address, subject, body):
    # format as a proper mail
    msg = Message()
    msg['Subject'] = subject
    msg['From'] = from_address
    msg['To'] = to_address
    # order is important here, Message() first, then Charset()
    #  then msg.set_charset()
    charset = email.charset.Charset("utf-8")
    charset.body_encoding = email.charset.QP
    msg.set_payload(body, charset)
    # and send it away
    sendmail = subprocess.Popen(
        [SENDMAIL_BINARY, "-oi", "-t"],
        stdin=subprocess.PIPE, universal_newlines=True)
    sendmail.stdin.write(msg.as_string())
    sendmail.stdin.close()
    ret = sendmail.wait()
    return ret

def send_summary_mail(pkgs, res, pkgs_kept_back, mem_log, dpkg_log_content):
    """ send mail (if configured in Unattended-Upgrade::Mail) """
    to_email = apt_pkg.config.find("Unattended-Upgrade::Mail", "")
    if not to_email:
        return
    if not os.path.exists(MAIL_BINARY) and not os.path.exists(SENDMAIL_BINARY):
        logging.error(_("No '/usr/bin/mail' or '/usr/sbin/sendmail',"
                        "can not send mail. "
                        "You probably want to install the 'mailx' package."))
        return
    # if the operation was successful and the user has requested to get
    # mails on on errors, just exit here
    if (res and
        # see Debian Bug #703621
        not re.search("^WARNING:", mem_log.getvalue(), re.MULTILINE) and
        apt_pkg.config.find_b(
            "Unattended-Upgrade::MailOnlyOnError", False)):
        return
    # Check if reboot-required flag is present
    reboot_flag_str = _(
        "[reboot required]") if os.path.isfile(REBOOT_REQUIRED_FILE) else ""
    # Check if packages are kept on hold
    hold_flag_str = _("[package on hold]") if pkgs_kept_back else ""
    logging.debug("Sending mail to '%s'" % to_email)
    subject = _(
        "{hold_flag}{reboot_flag} unattended-upgrades result for "
        "'{machine}': {result}").format(
            hold_flag=hold_flag_str, reboot_flag=reboot_flag_str,
            machine=host(), result=res).strip()
    body = _("Unattended upgrade returned: %s\n\n") % res
    if os.path.isfile(REBOOT_REQUIRED_FILE):
        body += _(
            "Warning: A reboot is required to complete this upgrade.\n\n")
    if res:
        body += _("Packages that were upgraded:\n")
    else:
        body += _("Packages that attempted to upgrade:\n")
    body += " " + wrap(pkgs, 70, " ")
    body += "\n"
    if pkgs_kept_back:
        body += _("Packages with upgradable origin but kept back:\n")
        body += " " + wrap(" ".join(pkgs_kept_back), 70, " ")
        body += "\n"
    body += "\n"
    if dpkg_log_content:
        body += _("Package installation log:") + "\n"
        body += dpkg_log_content
        body += "\n\n"
    body += _("Unattended-upgrades log:\n")
    body += mem_log.getvalue()

from_email = apt_pkg.config.find("Unattended-Upgrade::Sender", "root")

if os.path.exists(SENDMAIL_BINARY):
        ret = _send_mail_using_sendmail(from_email, to_email, subject, body)
    elif os.path.exists(MAIL_BINARY):
        ret = _send_mail_using_mailx(from_email, to_email, subject, body)
    else:
        raise AssertionError(
            "This should never be reached, if we are here we either "
            "have sendmail or mailx. Please report this as a bug.")
    logging.debug("mail returned: %s", ret)

def do_install(cache, pkgs_to_upgrade, blacklisted_pkgs, whitelisted_pkgs,
               options, logfile_dpkg):
    # set debconf to NON_INTERACTIVE, redirect output
    os.putenv("DEBIAN_FRONTEND", "noninteractive")
    setup_apt_listchanges()

logging.info(_("Writing dpkg log to '%s'"), logfile_dpkg)

marked_delete = [pkg for pkg in cache.get_changes() if pkg.marked_delete]
    if marked_delete:
        raise AssertionError(
            "Internal error. The following packages are marked for "
            "removal:%s" % "".join([pkg.name for pkg in marked_delete]))

pkg_install_success = False
    try:
        if (options.minimal_upgrade_steps or
            # COMPAT with the mispelling
            apt_pkg.config.find_b(
                "Unattended-Upgrades::MinimalSteps", False) or
            apt_pkg.config.find_b(
                "Unattended-Upgrade::MinimalSteps", False)):
            pidf = os.path.join(apt_pkg.config.find_dir("Dir"),
                                "var", "run", "unattended-upgrades.pid")
            with open(pidf, "w") as fp:
                fp.write("%s" % os.getpid())
            # try upgrade all "pkgs" in minimal steps
            pkg_install_success = upgrade_in_minimal_steps(
                cache, [pkg.name for pkg in pkgs_to_upgrade],
                blacklisted_pkgs, whitelisted_pkgs, logfile_dpkg,
                options.verbose or options.debug)
        else:
            pkg_install_success = upgrade_normal(
                cache, logfile_dpkg, options.verbose or options.debug)
    except Exception as e:
        # print unhandled exceptions here this way, while stderr is redirected
        os.write(2, ("Exception: %s\n" % e).encode('utf-8'))
        pkg_install_success = False

return pkg_install_success

def _setup_alternative_rootdir(rootdir):
    # clear system unattended-upgrade stuff
    apt_pkg.config.clear("Unattended-Upgrade")
    # read rootdir (taken from apt.Cache, but we need to run it
    # here before the cache gets initialized
    if os.path.exists(rootdir + "/etc/apt/apt.conf"):
        apt_pkg.read_config_file(apt_pkg.config,
                                 rootdir + "/etc/apt/apt.conf")
    if os.path.isdir(rootdir + "/etc/apt/apt.conf.d"):
        apt_pkg.read_config_dir(apt_pkg.config,
                                rootdir + "/etc/apt/apt.conf.d")
    logdir = os.path.join(rootdir, "var", "log", "unattended-upgrades")
    if not os.path.exists(logdir):
        os.makedirs(logdir)
    apt.apt_pkg.config.set("Unattended-Upgrade::LogDir", logdir)

def _get_logdir():
    logdir = apt_pkg.config.find_dir(
        "Unattended-Upgrade::LogDir",
        # COMPAT only
        apt_pkg.config.find_dir("APT::UnattendedUpgrades::LogDir",
                                "/var/log/unattended-upgrades/"))
    return logdir

def _setup_logging(options):
    # ensure this is run only once
    if len(logging.root.handlers) > 0:
        return

# init the logging
    logdir = _get_logdir()
    logfile = os.path.join(
        logdir,
        apt_pkg.config.find(
            "Unattended-Upgrade::LogFile",
            # COMPAT only
            apt_pkg.config.find("APT::UnattendedUpgrades::LogFile",
                                "unattended-upgrades.log")))
    if not options.dry_run and not os.path.exists(logdir):
        os.makedirs(logdir)

logging.basicConfig(level=logging.INFO,
                        format='%(asctime)s %(levelname)s %(message)s',
                        filename=logfile)
    # additional logging
    logger = logging.getLogger()
    mem_log = StringIO()
    if options.apt_debug:
        apt_pkg.config.set("Debug::pkgProblemResolver", "1")
        apt_pkg.config.set("Debug::pkgDepCache::AutoInstall", "1")
    if options.debug:
        logger.setLevel(logging.DEBUG)
        stdout_handler = logging.StreamHandler(sys.stdout)
        logger.addHandler(stdout_handler)
    elif options.verbose:
        logger.setLevel(logging.INFO)
        stdout_handler = logging.StreamHandler(sys.stdout)
        logger.addHandler(stdout_handler)
    if apt_pkg.config.find("Unattended-Upgrade::Mail", ""):
        mem_log_handler = logging.StreamHandler(mem_log)
        logger.addHandler(mem_log_handler)
    # Configure syslog if necessary
    syslogEnable = apt_pkg.config.find_b("Unattended-Upgrade::SyslogEnable",
                                         False)
    if syslogEnable:
        syslogFacility = apt_pkg.config.find(
            "Unattended-Upgrade::SyslogFacility",
            "daemon")
        syslogHandler = logging.handlers.SysLogHandler(
            address='/dev/log',
            facility=syslogFacility)
        syslogHandler.setFormatter(
            logging.Formatter("unattended-upgrade: %(message)s"))
        if syslogFacility.lower() in syslogHandler.facility_names.keys():
            logger.addHandler(syslogHandler)
            logging.info("Enabled logging to syslog via %s facility "
                         % syslogFacility)
        else:
            logging.warning("Syslog facility %s was not found"
                            % syslogFacility)
    return mem_log

def get_blacklisted_pkgs():
    return apt_pkg.config.value_list("Unattended-Upgrade::Package-Blacklist")

def get_whitelisted_pkgs():
    return apt_pkg.config.value_list("Unattended-Upgrade::Package-Whitelist")

def logged_in_users():
    """Return a list of logged in users"""
    # the "users" command always returns a single line with:
    # "user1, user1, user2"
    users = subprocess.check_output(
        USERS, universal_newlines=True).rstrip('\n')
    return set(users.split())

def reboot_if_requested_and_needed(shutdown_lock=0):
    """auto-reboot (if required and the config for this is set)"""
    if not os.path.exists(REBOOT_REQUIRED_FILE):
        return
    if not apt_pkg.config.find_b(
            "Unattended-Upgrade::Automatic-Reboot", False):
        return
    # see if we need to check for logged in users
    if not apt_pkg.config.find_b(
            "Unattended-Upgrade::Automatic-Reboot-WithUsers", True):
        users = logged_in_users()
        if users:
            msg = gettext.ngettext(
                "Found %s, but not rebooting because %s is logged in." % (
                    REBOOT_REQUIRED_FILE, users),
                "Found %s, but not rebooting because %s are logged in." % (
                    REBOOT_REQUIRED_FILE, users),
                len(users))
            logging.warning(msg)
            return
    # reboot at the specified time
    when = apt_pkg.config.find(
        "Unattended-Upgrade::Automatic-Reboot-Time", "now")
    if shutdown_lock > 0:
        os.close(shutdown_lock)
    logging.warning("Found %s, rebooting" % REBOOT_REQUIRED_FILE)
    subprocess.call(["/sbin/shutdown", "-r", when])

def write_stamp_file():
    statedir = os.path.join(apt_pkg.config.find_dir("Dir::State"), "periodic")
    if not os.path.exists(statedir):
        os.makedirs(statedir)
    with open(os.path.join(statedir, "unattended-upgrades-stamp"), "w"):
        pass

def try_to_upgrade(pkg, pkgs_to_upgrade, pkgs_kept_back, cache,
                   allowed_origins, blacklisted_pkgs, whitelisted_pkgs):

try:
        pkg.mark_upgrade(from_user=not pkg.is_auto_installed)
        if check_changes_for_sanity(cache, allowed_origins,
                                    blacklisted_pkgs, whitelisted_pkgs):
            # add to packages to upgrade
            pkgs_to_upgrade.append(pkg)
            # re-eval pkgs_kept_back as the resolver may fail to
            # directly upgrade a pkg, but that may work during
            # a subsequent operation, see debian bug #639840
            for pkgname in pkgs_kept_back:
                if (cache[pkgname].marked_install or
                        cache[pkgname].marked_upgrade):
                    pkgs_kept_back.remove(pkgname)
                    pkgs_to_upgrade.append(cache[pkgname])
        else:
            logging.debug("sanity check failed")
            rewind_cache(cache, pkgs_to_upgrade)
            pkgs_kept_back.append(pkg.name)
    except SystemError as e:
        # can't upgrade
        logging.warning(
            _("package '%s' upgradable but fails to "
                "be marked for upgrade (%s)"), pkg.name, e)
        rewind_cache(cache, pkgs_to_upgrade)
        pkgs_kept_back.append(pkg.name)

def calculate_upgradable_pkgs(cache, options, allowed_origins,
                              blacklisted_pkgs, whitelisted_pkgs):
    pkgs_to_upgrade = []
    pkgs_kept_back = []

# now do the actual upgrade
    for pkg in cache:
        if options.debug and pkg.is_upgradable:
            logging.debug("Checking: %s (%s)" % (
                pkg.name, getattr(pkg.candidate, "origins", [])))
        if (pkg.is_upgradable and
                not is_pkgname_in_blacklist(pkg.name, blacklisted_pkgs) and
                is_pkgname_in_whitelist(pkg.name, whitelisted_pkgs) and
                is_allowed_origin(pkg.candidate, allowed_origins)):

try_to_upgrade(pkg,
                           pkgs_to_upgrade,
                           pkgs_kept_back,
                           cache,
                           allowed_origins,
                           blacklisted_pkgs,
                           whitelisted_pkgs)
    return pkgs_to_upgrade, pkgs_kept_back

def get_dpkg_log_content(logfile_dpkg, install_start_time):
    logging.debug("Extracting content from '%s' since '%s'" % (
        logfile_dpkg, install_start_time))
    content = []
    found_start = False
    with io.open(logfile_dpkg, encoding='utf-8') as fp:
        # read until we find the last "Log started: "
        for line in fp.readlines():
            # scan for the first entry we need (minimal-step mode
            # creates a new stanza for each individual install)
            if not found_start and line.startswith("Log started: "):
                stanza_start = LoggingDateTime.from_string(
                    line[len("Log started: "):-1])
                if stanza_start >= install_start_time:
                    found_start = True
            if found_start:
                content.append(line)
    return "".join(content)

def get_auto_removable(cache):
    return set([pkg.name for pkg in cache
                if pkg.is_auto_removable])

def do_auto_remove(cache, auto_removable, logfile_dpkg, verbose=False):
    if not auto_removable:
        return True

for pkgname in auto_removable:
        logging.debug("marking %s for remove" % pkgname)
        cache[pkgname].mark_delete()
    logging.info(_("Packages that are auto removed: '%s'"),
                 " ".join(sorted(auto_removable)))

# do it
    res, error = cache_commit(cache, logfile_dpkg, verbose)
    if res:
        logging.info(_("Packages were successfully auto-removed"))
    else:
        logging.error(_("Auto-removing the packages failed!"))
        logging.error(_("Error message: '%s'"), error)
        logging.error(_("dpkg returned an error! See '%s' for details"),
                      logfile_dpkg)
    return res

def clean_downloaded_packages(fetcher):
    archivedir = os.path.dirname(
        apt_pkg.config.find_dir("Dir::Cache::archives"))
    for item in fetcher.items:
        if os.path.dirname(os.path.abspath(item.destfile)) == archivedir:
            try:
                os.unlink(item.destfile)
            except OSError:
                pass

def is_update_day():
    # check if patch days are configured
    patch_days = apt_pkg.config.value_list("Unattended-Upgrade::Update-Days")
    if not patch_days:
        return True
    # validate patch days
    today = date.today()
    # abbreviated localized dayname
    if today.strftime("%a") in patch_days:
        return True
    # full localized dayname
    if today.strftime("%A") in patch_days:
        return True
    # by number (Sun: 0, Mon: 1, ...)
    if today.strftime("%w") in patch_days:
        return True
    # today is not a patch day
    logging.info(
        "Skipping update check: today is '%s,%s,%s' but patch days are '%s'",
        today.strftime("%w"), today.strftime("%a"), today.strftime("%A"),
        patch_days)
    return False

def main(options, rootdir=""):
    # useful for testing
    if rootdir:
        _setup_alternative_rootdir(rootdir)

# setup logging
    mem_log = _setup_logging(options)

# check if today is a patch day
    if not is_update_day():
        return

# format (origin, archive), e.g. ("Ubuntu","dapper-security")
    allowed_origins = get_allowed_origins()

# pkgs that are (for some reason) not safe to install
    blacklisted_pkgs = get_blacklisted_pkgs()
    logging.info(_("Initial blacklisted packages: %s"),
                 " ".join(blacklisted_pkgs))

# install only these packages regardless of other upgrades available
    whitelisted_pkgs = get_whitelisted_pkgs()
    logging.info(_("Initial whitelisted packages: %s"),
                 " ".join(whitelisted_pkgs))

logging.info(_("Starting unattended upgrades script"))

# display available origin
    logging.info(_("Allowed origins are: %s"), allowed_origins)

# see debian #776752
    install_start_time = datetime.datetime.now().replace(microsecond=0)

# check if the journal is dirty and if so, take emergceny action
    # the alternative is to leave the system potentially unsecure until
    # the user comes in and fixes
    if (is_dpkg_journal_dirty() and
        apt_pkg.config.find_b(
            "Unattended-Upgrade::AutoFixInterruptedDpkg", True)):
        # ensure the dpkg database is not already locked (LP: #754330)
        admindir = os.path.dirname(apt_pkg.config.find("Dir::State::Status"))
        lockfd = apt_pkg.get_lock(os.path.join(admindir, "lock"), False)
        if lockfd > 0:
            logging.warning(
                _("Unclean dpkg state detected, trying to correct"))
            print(_("Unclean dpkg state detected, trying to correct"))
            env = copy.copy(os.environ)
            env["DEBIAN_FRONTEND"] = "noninteractive"
            try:
                os.close(lockfd)
                output = subprocess.check_output(
                    ["dpkg", "--force-confold", "--configure", "-a"],
                    env=env,
                    universal_newlines=True)
            except subprocess.CalledProcessError as e:
                output = e.output
            logging.warning(_("dpkg --configure -a output:\n%s"), output)
        else:
            logging.debug("Unclean dpkg state, but locked, another package "
                          "manager working?")

# check and get lock
    try:
        apt_pkg.pkgsystem_lock()
    except SystemError as e:
        logging.error(_("Lock could not be acquired (another package "
                        "manager running?)"))
        print(_("Cache lock can not be acquired, exiting"))
        sys.exit(1)

# get a cache
    cache = UnattendedUpgradesCache(rootdir=rootdir,
                                    allowed_origins=allowed_origins)
    if cache._depcache.broken_count > 0:
        print(_("Cache has broken packages, exiting"))
        logging.error(_("Cache has broken packages, exiting"))
        sys.exit(1)

# FIXME: make this into a ContextManager
    # be nice when calculating the upgrade as its pretty CPU intensive
    old_priority = os.nice(0)
    try:
        # Check that we will be able to restore the priority
        os.nice(-1)
        os.nice(20)
    except OSError as e:
        if e.errno in (errno.EPERM, errno.EACCES):
            pass
        else:
            raise

# speed things up with latest apt
    actiongroup = apt_pkg.ActionGroup(cache._depcache)
    actiongroup  # pyflakes

# find out about the packages that are upgradable (in a allowed_origin)
    pkgs_to_upgrade, pkgs_kept_back = calculate_upgradable_pkgs(
        cache, options, allowed_origins, blacklisted_pkgs, whitelisted_pkgs)
    pkgs_to_upgrade.sort(key=lambda p: p.name)
    pkgs = "\n".join([pkg.name for pkg in pkgs_to_upgrade])
    logging.debug("pkgs that look like they should be upgraded: %s" % pkgs)

# FIXME: make this into a ContextManager
    # stop being nice
    os.nice(old_priority - os.nice(0))

# download what looks good
    if options.debug:
        fetcher = apt_pkg.Acquire(apt.progress.text.AcquireProgress())
    else:
        fetcher = apt_pkg.Acquire()
    list = apt_pkg.SourceList()
    list.read_main_list()
    recs = cache._records
    pm = apt_pkg.PackageManager(cache._depcache)
    try:
        pm.get_archives(fetcher, list, recs)
    except SystemError as e:
        logging.error(_("GetArchives() failed: '%s'"), e)
    res = fetcher.run()
    logging.debug("fetch.run() result: %s", res)

if dpkg_conffile_prompt():
        # now check the downloaded debs for conffile conflicts and build
        # a blacklist
        for item in fetcher.items:
            logging.debug("%s" % item)
            if item.status == item.STAT_ERROR:
                print(_("An error occurred: '%s'") % item.error_text)
                logging.error(_("An error occurred: '%s'"), item.error_text)
            if not item.complete:
                print(_("The URI '%s' failed to download, aborting") %
                      item.desc_uri)
                logging.error(_("The URI '%s' failed to download, aborting"),
                              item.desc_uri)
                sys.exit(1)
            if not os.path.exists(item.destfile):
                print(_("Download finished, but file '%s' not there?!?") %
                      item.destfile)
                logging.error("Download finished, but file '%s' not "
                              "there?!?", item.destfile)
                sys.exit(1)
            if not item.is_trusted:
                blacklisted_pkgs.append(pkgname_from_deb(item.destfile))
            if conffile_prompt(item.destfile):
                # skip package (means to re-run the whole marking again
                # and making sure that the package will not be pulled in by
                # some other package again!)
                #
                # print to stdout to ensure that this message is part of
                # the cron mail (only if no summary mail is requested)
                email = apt_pkg.config.find("Unattended-Upgrade::Mail", "")
                if not email:
                    print(_("Package '%s' has conffile prompt and needs "
                            "to be upgraded manually") %
                          pkgname_from_deb(item.destfile))
                # log to the logfile
                logging.warning(_("Package '%s' has conffile prompt and "
                                  "needs to be upgraded manually"),
                                pkgname_from_deb(item.destfile))
                blacklisted_pkgs.append(pkgname_from_deb(item.destfile))
                pkgs_kept_back.append(pkgname_from_deb(item.destfile))

# redo the selection about the packages to upgrade based on the new
        # blacklist
        logging.debug("blacklist: %s" % blacklisted_pkgs)
        # whitelist
        logging.debug("whitelist: %s" % whitelisted_pkgs)
        # find out about the packages that are upgradable (in a allowed_origin)
        if len(blacklisted_pkgs) > 0 or len(whitelisted_pkgs) > 0:
            cache.clear()
            old_pkgs_to_upgrade = pkgs_to_upgrade[:]
            pkgs_to_upgrade = []
            for pkg in old_pkgs_to_upgrade:
                logging.debug("Checking the black and whitelist: %s" %
                              (pkg.name))
                pkg.mark_upgrade(from_user=not pkg.is_auto_installed)
                if check_changes_for_sanity(cache,
                                            allowed_origins,
                                            blacklisted_pkgs,
                                            whitelisted_pkgs):
                    pkgs_to_upgrade.append(pkg)
                else:
                    if not (pkg.name in pkgs_kept_back):
                        pkgs_kept_back.append(pkg.name)
                    logging.info(_("package '%s' not upgraded"), pkg.name)
                    cache.clear()
                    for pkg2 in pkgs_to_upgrade:
                        pkg2.mark_upgrade(from_user=not pkg2.is_auto_installed)
    else:
        logging.debug("dpkg is configured not to cause conffile prompts")

# auto-removal
    previous_autoremovals = get_auto_removable(cache)
    if apt_pkg.config.find_b(
            "Unattended-Upgrade::Remove-Unused-Dependencies", False):
        pending_autoremovals = previous_autoremovals
    else:
        pending_autoremovals = []

# exit if there is nothing to do and nothing to report
    if (len(pending_autoremovals) == 0 and
            len(pkgs_to_upgrade) == 0 and
            len(pkgs_kept_back) == 0):
        logging.info(_("No packages found that can be upgraded unattended "
                       "and no pending auto-removals"))
        # FIXME: DRY violation, write_stamp_file() is used below as well
        write_stamp_file()
        # check if we couldn't reboot on previous run because
        # a user was logged-in at this time
        reboot_if_requested_and_needed()
        return

# check if its configured for install on shutdown, if so, the
    # environment UNATTENDED_UPGRADES_FORCE_INSTALL_ON_SHUTDOWN will
    # be set by the unatteded-upgrades-shutdown script
    if ("UNATTENDED_UPGRADES_FORCE_INSTALL_ON_SHUTDOWN" not in os.environ and
            apt_pkg.config.find_b(
                "Unattended-Upgrade::InstallOnShutdown", False)):
        logger = logging.getLogger()
        logger.debug("Configured to install on shutdown, so exiting now")
        return

# check if we are in dry-run mode
    if options.dry_run:
        logging.info("Option --dry-run given, *not* performing real actions")
        apt_pkg.config.set("Debug::pkgDPkgPM", "1")

# do the install based on the new list of pkgs
    pkgs = " ".join([pkg.name for pkg in pkgs_to_upgrade])
    logging.info(_("Packages that will be upgraded: %s"), pkgs)

# get log
    logfile_dpkg = os.path.join(_get_logdir(), 'unattended-upgrades-dpkg.log')
    if not os.path.exists(logfile_dpkg):
        with open(logfile_dpkg, 'w'):
            pass

# only perform install step if we actually have packages to install
    pkg_install_success = True
    shutdown_lock = -1
    if len(pkgs_to_upgrade) > 0:
        # lock for the shutdown check - its fine if the system
        # is shutdown while downloading but not so much while installing
        shutdown_lock = apt_pkg.get_lock("/var/run/unattended-upgrades.lock")
        # do install
        pkg_install_success = do_install(cache,
                                         pkgs_to_upgrade,
                                         blacklisted_pkgs,
                                         whitelisted_pkgs,
                                         options,
                                         logfile_dpkg)

# now check if any auto-removing needs to be done
    cache = UnattendedUpgradesCache(
        rootdir=rootdir, allowed_origins=allowed_origins)
    if cache._depcache.broken_count > 0:
        print(_("Cache has broken packages, exiting"))
        logging.error(_("Cache has broken packages, exiting"))
        sys.exit(1)

# the user wants *all* auto-removals to be removed
    if apt_pkg.config.find_b(
            "Unattended-Upgrade::Remove-Unused-Dependencies", False):
        auto_removals = get_auto_removable(cache)
        pkg_install_success &= do_auto_remove(
            cache, auto_removals, logfile_dpkg,
            options.verbose or options.debug)
    # the user wants *only new* auto-removals to be removed
    elif apt_pkg.config.find_b(
            "Unattended-Upgrade::Remove-New-Unused-Dependencies", True):
        # calculate the new auto-removals
        new_pending_autoremovals = get_auto_removable(cache)
        auto_removals = new_pending_autoremovals - previous_autoremovals
        pkg_install_success &= do_auto_remove(
            cache, auto_removals, logfile_dpkg,
            options.verbose or options.debug)

logging.debug("InstCount=%i DelCount=%i BrokenCount=%i"
                  % (cache._depcache.inst_count,
                     cache._depcache.del_count,
                     cache._depcache.broken_count))

# send a mail (if needed)
    if not options.dry_run:
        log_content = get_dpkg_log_content(logfile_dpkg, install_start_time)
        send_summary_mail(
            pkgs, pkg_install_success, pkgs_kept_back, mem_log, log_content)

# clean after success install (if needed)
    keep_key = "Unattended-Upgrade::Keep-Debs-After-Install"
    if (not apt_pkg.config.find_b(keep_key, False) and
            not options.dry_run and
            pkg_install_success):
        clean_downloaded_packages(fetcher)

# FIXME: DRY violation, write_stamp_file() is used above as well
    # write timestamp file
    write_stamp_file()

# check if the user wants a reboot
    if not options.dry_run:
        reboot_if_requested_and_needed(shutdown_lock)

if __name__ == "__main__":
    localesApp = "unattended-upgrades"
    localesDir = "/usr/share/locale"
    gettext.bindtextdomain(localesApp, localesDir)
    gettext.textdomain(localesApp)

# this ensures the commandline is logged in /var/log/apt/history.log
    apt_pkg.config.set("Commandline::AsString", " ".join(sys.argv))

# init the options
    parser = OptionParser()
    parser.add_option("-d", "--debug",
                      action="store_true", default=False,
                      help=_("print debug messages"))
    parser.add_option("", "--apt-debug",
                      action="store_true", default=False,
                      help=_("make apt/libapt print verbose debug messages"))
    parser.add_option("-v", "--verbose",
                      action="store_true", default=False,
                      help=_("print info messages"))
    parser.add_option("", "--dry-run",
                      action="store_true", default=False,
                      help=_("Simulation, download but do not install"))
    parser.add_option("", "--minimal-upgrade-steps",
                      action="store_true", default=False,
                      help=_("Upgrade in minimal steps (and allow "
                             "interrupting with SIGINT"))
    parser.add_option("", "--minimal_upgrade_steps",
                      action="store_true",
                      help=SUPPRESS_HELP,
                      default=False)
    (options, args) = parser.parse_args()

if os.getuid() != 0:
        print(_("You need to be root to run this application"))
        sys.exit(1)

# ensure that we are not killed when the terminal goes away e.g. on
    # shutdown
    signal.signal(signal.SIGHUP, signal.SIG_IGN)

# run the main code
    main(options)