[Summary: What seems to have been a kernel update caused a couple of things, including internet access, to stop working, and booting older kernels gives me a low graphics mode issue. Reading up on that, I looked for /etc/lightdm/lightdm.conf, but found no such file at all, yet Unity does work (without internet, audio or webcam) if I boot the latest kernel 4.4.0-77-generic.]
I've never written here before, and, English is my third language, so I actually feel a bit embarrassed about writing this. There are basically so many things going wrong that I can barely believe it myself. Not that I'm not good enough at reading and writing in English, it's just the "stage fright" of having to participate in a public discussion about something I don't know that much about.
So my problem is, after an update that required me to restart my laptop [added kernel 4.4.0-77-generic and some stuff with the syllable lib, all of that stuff, save for something unicode-related seems to have to do with libreoffice, see log entry below for the specific package names], it wouldn't connect to the internet, and trying with another cable didn't fix it. Clicking on the leftmost icon in the top right corner of the screen gave me a menu whose first item read "no network device available". Then I realised there wasn't any sound either despite the volume somehow having reset itself to 100%. In the audio settings it says "dummy output". Neither speakers nor headphones worked. I have also tried connecting a USB microphone and that doesn't work either. Interestingly, connecting a thumb drive does work. Inserting an SD card into the laptop's SD card slot doesn't. The DVD drive, I'm not sure: it can detect disks but I get an error message saying they can't be mounted even though it actually shows the names of the disks in those messages [edit: it's just complaining about only being able to mount them read-only, which I guess might be reasonable. I obviously can't check whether I get similar messages on 14.04 as that would require somehow running it from another drive]. Taking a closer look at the top of the screen I found there wasn't any Bluetooth icon. The Bluetooth settings say "no Bluetooth adapter found". I'm not really that concerned about the latter as I don't use Bluetooth anyway. Also, I checked the built-in webcam and it doesn't get detected.
To be able to send this question, I'm using the live DVD that I installed Ubuntu from which was 14.04, meaning some websites aren't even working properly as they expect newer versions of Firefox.
I tried rebooting with some older versions of the kernel [4.4.0-75-generic and the previous one: 4.4.0-72-generic] but that just leaves me with a "The system is running in low-graphics mode" message saying "Your screen, graphics card, and input device settings could not be detected correctly. You will need to configure these yourself". Then I told it to "try running with default graphics mode" which just gives me a black screen with a white blinking underscore in the top left corner and it stays so even if I wait five minutes (it usually takes almost a minute to boot). [Also, Ctrl-alt-f1 did nothing.]
In case it helps, I also noticed the icons on the dashbar in the left side got reset to their default size by the update.
Edit: I've looked at other questions about networking issues (as I guess fixing those may make the other ones a bit easier to fix) and did some tests they mentioned: ifconfig output on "updated" system:
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:1332 errors:0 dropped:0 overruns:0 frame:0
TX packets:1332 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1
RX bytes:98912 (98.9 KB) TX bytes:98912 (98.9 KB)
Output with DVD:
eth0 Link encap:Ethernet HWaddr 30:f9:ed:be:67:db
inet addr:192.168.2.100 Bcast:192.168.2.255 Mask:255.255.255.0
inet6 addr: fe80::32f9:edff:febe:67db/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2514 errors:0 dropped:0 overruns:0 frame:0
TX packets:1455 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:3562860 (3.5 MB) TX bytes:128889 (128.8 KB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:160 errors:0 dropped:0 overruns:0 frame:0
TX packets:160 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:15050 (15.0 KB) TX bytes:15050 (15.0 KB)
wlan0 Link encap:Ethernet HWaddr 08:3e:8e:c1:f4:77
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
lspci output on "updated" system:
00:00.0 Host bridge: Intel Corporation 3rd Gen Core processor DRAM Controller (rev 09)
00:01.0 PCI bridge: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor PCI Express Root Port (rev 09)
00:14.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB xHCI Host Controller (rev 04)
00:16.0 Communication controller: Intel Corporation 7 Series/C210 Series Chipset Family MEI Controller #1 (rev 04)
00:1a.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #2 (rev 04)
00:1b.0 Audio device: Intel Corporation 7 Series/C210 Series Chipset Family High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 1 (rev c4)
00:1c.1 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 2 (rev c4)
00:1c.2 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 3 (rev c4)
00:1d.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation HM76 Express Chipset LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation 7 Series Chipset Family 6-port SATA Controller [AHCI mode] (rev 04)
00:1f.3 SMBus: Intel Corporation 7 Series/C210 Series Chipset Family SMBus Controller (rev 04)
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Thames [Radeon HD 7550M/7570M/7650M]
01:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Turks/Whistler HDMI Audio [Radeon HD 6000 Series]
07:00.0 Network controller: Qualcomm Atheros AR9485 Wireless Network Adapter (rev 01)
08:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS5209 PCI Express Card Reader (rev 01)
09:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 07)
Output with DVD seems to be the same.
sudo lshw -C network output on "updated" system:
*-network UNCLAIMED
description: Network controller
product: AR9485 Wireless Network Adapter
vendor: Qualcomm Atheros
physical id: 0
bus info: pci@0000:07:00.0
version: 01
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress bus_master cap_list
configuration: latency=0
resources: memory:c1200000-c127ffff memory:c1280000-c128ffff
*-network UNCLAIMED
description: Ethernet controller
product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
vendor: Realtek Semiconductor Co., Ltd.
physical id: 0
bus info: pci@0000:09:00.0
version: 07
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress msix vpd bus_master cap_list
configuration: latency=0
resources: ioport:2000(size=256) memory:c1004000-c1004fff memory:c1000000-c1003fff
Using the DVD, I get this:
*-network
description: Wireless interface
product: AR9485 Wireless Network Adapter
vendor: Qualcomm Atheros
physical id: 0
bus info: pci@0000:07:00.0
logical name: wlan0
version: 01
serial: 08:3e:8e:c1:f4:77
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress bus_master cap_list rom ethernet physical wireless
configuration: broadcast=yes driver=ath9k driverversion=3.13.0-32-generic firmware=N/A latency=0 link=no multicast=yes wireless=IEEE 802.11bgn
resources: irq:16 memory:c1200000-c127ffff memory:c1500000-c150ffff
*-network
description: Ethernet interface
product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
vendor: Realtek Semiconductor Co., Ltd.
physical id: 0
bus info: pci@0000:09:00.0
logical name: eth0
version: 07
serial: 30:f9:ed:be:67:db
size: 100Mbit/s
capacity: 1Gbit/s
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl8168e-3_0.0.4 03/27/12 ip=192.168.2.100 latency=0 link=yes multicast=yes port=MII speed=100Mbit/s
resources: irq:43 ioport:2000(size=256) memory:c1004000-c1004fff memory:c1000000-c1003fff
Also, I checked the file /var/log/apt/history.log as suggested below and found this:
Start-Date: 2017-05-03 12:25:23
Commandline: aptdaemon role='role-commit-packages' sender=':1.98'
Install: linux-signed-image-4.4.0-77-generic:amd64 (4.4.0-77.98, automatic), linux-image-4.4.0-77-generic:amd64 (4.4.0-77.98, automatic)
Upgrade: libreoffice-style-breeze:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libreoffice-math:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libreoffice-core:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libicu55:amd64 (55.1-7ubuntu0.1, 55.1-7ubuntu0.2), libreoffice-gtk:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libreoffice-style-human:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libreoffice-style-galaxy:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libreoffice-base-core:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libreoffice-ogltrans:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libreoffice-impress:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), ure:amd64 (5.1.6~rc2-0ubuntu1~xenial1, 5.1.6~rc2-0ubuntu1~xenial2), libreoffice-writer:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libreoffice-common:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), fonts-opensymbol:amd64 (2:102.7+LibO5.1.6~rc2-0ubuntu1~xenial1, 2:102.7+LibO5.1.6~rc2-0ubuntu1~xenial2), libreoffice-pdfimport:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), uno-libs3:amd64 (5.1.6~rc2-0ubuntu1~xenial1, 5.1.6~rc2-0ubuntu1~xenial2), libreoffice-gnome:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libreoffice-calc:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libreoffice-draw:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2), libreoffice-avmedia-backend-gstreamer:amd64 (1:5.1.6~rc2-0ubuntu1~xenial1, 1:5.1.6~rc2-0ubuntu1~xenial2)
End-Date: 2017-05-03 12:27:16