Comment 46 for bug 1690980

Here's unattended-upgrades.log when the reboot did not cause an inconsistent state:

2017-07-26 08:33:37,462 INFO Initial blacklisted packages:
2017-07-26 08:33:37,463 INFO Initial whitelisted packages:
2017-07-26 08:33:37,463 INFO Starting unattended upgrades script
2017-07-26 08:33:37,463 INFO Allowed origins are: ['o=Ubuntu,a=xenial', 'o=Ubuntu,a=xenial-security', 'o=UbuntuESM,a=xenial']
2017-07-26 08:38:14,276 INFO Packages that will be upgraded: apparmor apport apport-gtk apt-transport-https bash bind9-host cpp-5 curl dbus dbus-x11 distro-info-data dnsutils eject evince evince-common firefox firefox-locale-en fonts-opensymbol g++-5 gcc-5 gcc-5-base ghostscript ghostscript-x gir1.2-gst-plugins-base-1.0 gir1.2-javascriptcoregtk-4.0 gir1.2-webkit2-4.0 gstreamer1.0-alsa gstreamer1.0-plugins-base gstreamer1.0-plugins-base-apps gstreamer1.0-plugins-good gstreamer1.0-pulseaudio gstreamer1.0-x imagemagick imagemagick-6.q16 imagemagick-common libapparmor-perl libapparmor1 libapt-inst2.0 libarchive13 libasan2 libasn1-8-heimdal libatomic1 libbind9-140 libc-bin libc-dev-bin libc6 libc6-dbg libc6-dev libcc1-0 libcilkrts5 libcurl3 libcurl3-gnutls libdbus-1-3 libdns-export162 libdns162 libevdocument3-4 libevent-2.0-5 libevview3-3 libexpat1 libfreetype6 libgc1c2 libgcc-5-dev libgcrypt20 libgd3 libgnutls-openssl27 libgnutls30 libgomp1 libgs9 libgs9-common libgssapi3-heimdal libgstreamer-plugins-base1.0-0 libgstreamer-plugins-good1.0-0 libhcrypto4-heimdal libheimbase1-heimdal libheimntlm0-heimdal libhogweed4 libhx509-5-heimdal libicu55 libisc-export160 libisc160 libisccc140 libisccfg140 libitm1 libjasper1 libjavascriptcoregtk-4.0-18 libjbig2dec0 libkrb5-26-heimdal libldap-2.4-2 liblightdm-gobject-1-0 liblsan0 liblwres141 libmagickcore-6.q16-2 libmagickcore-6.q16-2-extra libmagickwand-6.q16-2 libminiupnpc10 libmpx0 libmwaw-0.3-3 libnettle6 libnl-3-200 libnl-genl-3-200 libnm-glib-vpn1 libnm-glib4 libnm-gtk-common libnm-gtk0 libnm-util2 libnm0 libnma-common libnma0 libnspr4 libnss3 libnss3-nssdb liboxideqt-qmlplugin liboxideqtcore0 liboxideqtquick0 libpcsclite1 libpoppler-glib8 libpoppler58 libpython2.7 libpython2.7-minimal libpython2.7-stdlib libpython3.5 libpython3.5-minimal libpython3.5-stdlib libquadmath0 libreoffice-avmedia-backend-gstreamer libreoffice-base-core libreoffice-calc libreoffice-common libreoffice-core libreoffice-draw libreoffice-gnome libreoffice-gtk libreoffice-impress libreoffice-math libreoffice-ogltrans libreoffice-pdfimport libreoffice-style-breeze libreoffice-style-galaxy libreoffice-writer libroken18-heimdal librtmp1 libsmbclient libsndfile1 libssl1.0.0 libstdc++-5-dev libstdc++6 libtasn1-6 libtiff5 libtracker-sparql-1.0-0 libtsan0 libubsan0 libvncclient1 libwbclient0 libwebkit2gtk-4.0-37 libwebkit2gtk-4.0-37-gtk2 libwind0-heimdal libxml2 libxpm4 libxslt1.1 lightdm lintian linux-firmware linux-generic linux-headers-generic linux-image-generic linux-libc-dev locales login multiarch-support network-manager network-manager-gnome ntfs-3g openssl oxideqt-codecs passwd poppler-utils python2.7 python2.7-minimal python3-apport python3-cryptography python3-pil python3-problem-report python3-uno python3.5 python3.5-minimal samba-libs sudo tar tcpdump thunderbird thunderbird-gnome-support thunderbird-locale-en thunderbird-locale-en-us tzdata uno-libs3 ure vim vim-common vim-runtime vim-tiny xserver-common xserver-xorg-core
2017-07-26 08:38:14,276 INFO Writing dpkg log to '/var/log/unattended-upgrades/unattended-upgrades-dpkg.log'
2017-07-26 08:38:15,406 WARNING SIGTERM received, will stop

Here is the unattended-upgrades.log which produced the inconsistent state:

2017-07-26 09:19:02,321 INFO Initial blacklisted packages:
2017-07-26 09:19:02,322 INFO Initial whitelisted packages:
2017-07-26 09:19:02,322 INFO Starting unattended upgrades script
2017-07-26 09:19:02,322 INFO Allowed origins are: ['o=Ubuntu,a=xenial', 'o=Ubuntu,a=xenial-security', 'o=UbuntuESM,a=xenial']
2017-07-26 09:19:02,323 WARNING Unclean dpkg state detected, trying to correct
2017-07-26 09:19:03,101 WARNING dpkg --configure -a output:
Setting up man-db (2.7.5-1) ...
Setting up login (1:4.2-3.1ubuntu5.3) ...

2017-07-26 09:23:24,398 INFO Packages that will be upgraded: apparmor apport apport-gtk apt-transport-https bind9-host cpp-5 curl dbus dbus-x11 distro-info-data dnsutils eject evince evince-common firefox firefox-locale-en fonts-opensymbol g++-5 gcc-5 gcc-5-base ghostscript ghostscript-x gir1.2-gst-plugins-base-1.0 gir1.2-javascriptcoregtk-4.0 gir1.2-webkit2-4.0 gstreamer1.0-alsa gstreamer1.0-plugins-base gstreamer1.0-plugins-base-apps gstreamer1.0-plugins-good gstreamer1.0-pulseaudio gstreamer1.0-x imagemagick imagemagick-6.q16 imagemagick-common libapparmor-perl libapparmor1 libapt-inst2.0 libarchive13 libasan2 libasn1-8-heimdal libatomic1 libbind9-140 libc-bin libc-dev-bin libc6 libc6-dbg libc6-dev libcc1-0 libcilkrts5 libcurl3 libcurl3-gnutls libdbus-1-3 libdns-export162 libdns162 libevdocument3-4 libevent-2.0-5 libevview3-3 libexpat1 libfreetype6 libgc1c2 libgcc-5-dev libgcrypt20 libgd3 libgnutls-openssl27 libgnutls30 libgomp1 libgs9 libgs9-common libgssapi3-heimdal libgstreamer-plugins-base1.0-0 libgstreamer-plugins-good1.0-0 libhcrypto4-heimdal libheimbase1-heimdal libheimntlm0-heimdal libhogweed4 libhx509-5-heimdal libicu55 libisc-export160 libisc160 libisccc140 libisccfg140 libitm1 libjasper1 libjavascriptcoregtk-4.0-18 libjbig2dec0 libkrb5-26-heimdal libldap-2.4-2 liblightdm-gobject-1-0 liblsan0 liblwres141 libmagickcore-6.q16-2 libmagickcore-6.q16-2-extra libmagickwand-6.q16-2 libminiupnpc10 libmpx0 libmwaw-0.3-3 libnettle6 libnl-3-200 libnl-genl-3-200 libnm-glib-vpn1 libnm-glib4 libnm-gtk-common libnm-gtk0 libnm-util2 libnm0 libnma-common libnma0 libnspr4 libnss3 libnss3-nssdb liboxideqt-qmlplugin liboxideqtcore0 liboxideqtquick0 libpcsclite1 libpoppler-glib8 libpoppler58 libpython2.7 libpython2.7-minimal libpython2.7-stdlib libpython3.5 libpython3.5-minimal libpython3.5-stdlib libquadmath0 libreoffice-avmedia-backend-gstreamer libreoffice-base-core libreoffice-calc libreoffice-common libreoffice-core libreoffice-draw libreoffice-gnome libreoffice-gtk libreoffice-impress libreoffice-math libreoffice-ogltrans libreoffice-pdfimport libreoffice-style-breeze libreoffice-style-galaxy libreoffice-writer libroken18-heimdal librtmp1 libsmbclient libsndfile1 libssl1.0.0 libstdc++-5-dev libstdc++6 libtasn1-6 libtiff5 libtracker-sparql-1.0-0 libtsan0 libubsan0 libvncclient1 libwbclient0 libwebkit2gtk-4.0-37 libwebkit2gtk-4.0-37-gtk2 libwind0-heimdal libxml2 libxpm4 libxslt1.1 lightdm lintian linux-firmware linux-generic linux-headers-generic linux-image-generic linux-libc-dev locales multiarch-support network-manager network-manager-gnome ntfs-3g openssl oxideqt-codecs passwd poppler-utils python2.7 python2.7-minimal python3-apport python3-cryptography python3-pil python3-problem-report python3-uno python3.5 python3.5-minimal samba-libs sudo tcpdump thunderbird thunderbird-gnome-support thunderbird-locale-en thunderbird-locale-en-us tzdata uno-libs3 ure vim vim-common vim-runtime vim-tiny xserver-common xserver-xorg-core
2017-07-26 09:23:24,402 INFO Writing dpkg log to '/var/log/unattended-upgrades/unattended-upgrades-dpkg.log'
2017-07-26 09:24:54,269 WARNING SIGTERM received, will stop
2017-07-26 09:24:54,270 WARNING SIGTERM received, will stop
2017-07-26 09:24:54,615 WARNING SIGTERM received, will stop

And part of the corresponding unattended-upgrades-dpkg.log file:

Preparing to unpack .../linux-image-generic_4.4.0.87.93_amd64.deb ...^M
Unpacking linux-image-generic (4.4.0.87.93) over (4.4.0.38.40) ...^M
Selecting previously unselected package linux-headers-4.4.0-87.^M
Preparing to unpack .../linux-headers-4.4.0-87_4.4.0-87.110_all.deb ...^M
Unpacking linux-headers-4.4.0-87 (4.4.0-87.110) ...^M
SIGTERM received, will stop
E:Sub-process /usr/bin/dpkg exited unexpectedly