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16.04 interview questions

Top 16.04 frequently asked interview questions


How do I downgrade Gedit to a previous (3.10.4) Version in Ubuntu 16.04 LTS

As the title already says: I have some plug-ins which don't run with gedit 3.18.3 which is shipped with Ubuntu 16.04 LTS.

How can I downgrade to the version 3.10.4 which was used in Ubuntu 14.04 LTS and Ubuntu 15.10 and get all the plug-ins possible installed?

And how do I revert it back to 3.18.3 if 3.10.4 is not needed any more.


Source: (StackOverflow)

Ubuntu Server 16.04 installs on /sdc but fails to boot

I am doing a clean install of Ubuntu Server 16.04 LTS on a machine with a single internal SSD. After completing the install, the system fails to boot and prints a single line fsck output, with the rest of the screen entirely blank.

enter image description here

This very same server installs Ubuntu Server 14.04.4 LTS just fine, so this is very specific to 16.04 LTS. I've tried installing every which way I can think of in 16 and I get the same results every time: installation completes with no errors, but upon reboot I get a black screen with that one line of fsck output after rebooting :(

I noticed that one big difference between 14 and 16 installs on this server machine (which is unexceptional, it's just a generic Broadwell i5 box with 16GB RAM and Samsung 850 EVO SSD) is that Ubuntu 14 detects and installs the drive as /sda whereas Ubuntu 16 detects and installs the drive as /sdc -- furthermore, Ubuntu 16 detects the USB flash drive with the Ubuntu install as /sda! This strikes me as .. very incorrect.

enter image description here

How can I get the Ubuntu Server 16.04 install to stop treating the USB installation drive as /sda?

Edit: per request, here's the output of fdisk after pressing alt+ near the end of the install

fdisk during install

here's the output of

# mkdir /mnt/ssd
# mount /dev/sdc1 /mnt/ssd
# nano /mnt/ssd/etc/fstab

fstab in nano

When I boot into "rescue mode" from the USB install media (no option to boot in recovery mode is presented to me), I get the following options for "device to use as a root file system"

/dev/sda1  
/dev/sda5  
/dev/sdb1  
Assemble RAID array  
Do not use a root file system  

Notice that no /sdc filesystem is detected or shown. However, when I enter console under /sda1 and fdisk -l I do see what I installed as /sdc!

recovery mode fdisk -l

I tried "Reinstall GRUB boot loader" targeting /sda1 and I get an error. I tried it again with /sda as the target, and that seemed to work.

But rebooting, same black screen, single like fsck output unfortunately.


Source: (StackOverflow)

Why disabling "Secure Boot" is enforced policy when installing 3rd party modules

When installing 16.04, I was asked to turn off "Secure Boot" if I wanted to install 3rd party modules/drivers.

I did not comply.

And when I installed manually the only 3rd party drivers I use (bcmwl-kernel-source), I was asked again (during the installation of the package) to turn off "Secure Boot".

Using bcmwl-kernel-source was perfectly fine with Secure Boot in 15.10. This does not seem to be related to a bug to me.

So this does look like Ubuntu refuse to sign anymore the 3rd party drivers/modules to make it work (??) with "Secure Boot". Or seem to consider 3rd party modules as insecure and breaking "Secure Boot" hence inforcing to disable it to make it clear ?? Am I right ?


Source: (StackOverflow)

Why is my network interface named enp0s25 instead of eth0?

A lot of my scripts stopped working after installing Ubuntu 15.10 and I have trouble remembering this new name as I was used to ethx and wlanx for years. Is there a reason for this change? Do I have to get used to this or can I just rename it and go back to good old eth0?

$ ifconfig

enp0s25   Link encap:Ethernet  HWaddr 77:5a:5e:a6:86:d5  
      inet addr:192.168.31.239  Bcast:192.168.31.255  Mask:255.255.255.0
      inet6 addr: fe80::725a:b6ff:fea6:86d7/64 Scope:Link
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      RX packets:4833 errors:1332 dropped:0 overruns:0 frame:666
      TX packets:5589 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:3266446 (3.2 MB)  TX bytes:1046654 (1.0 MB)
      Interrupt:20 Memory:d3500000-d3520000

Source: (StackOverflow)

How do I make the Caps Lock key a third Shift key?

How do I make the Caps Lock key work just like another Shift key?

There are loads of questions here about reassigning it, or having it launch a custom command. I just want it to work like another Shift key. I don't want any other keys to change what they do, just that one.

Keyboard Layout/Caps Lock key behavior won't do it, I don't understand how to remap it in CCSM.

I'm using a UK keyboard now but I learned to type on a US keyboard, the smaller left Shift key is DRIVING ME NUTS.


Source: (StackOverflow)

Ubuntu 16.04 LTS Shown in Upgrade Manager Now

I see the next upgrade available as 16.04 LTS shown in update manager.

But the release date (from wiki) is written as April 2016. And it's not shown in Ubuntu page yet.

Why is it already available to upgrade now? If it's not official, why is it listed as an option in the update manager?

Thanks for any information.

(I'm in the process of upgrading my Ubuntu Gnome 14.04 in my Dell Venue 11 Pro 7140. Everything works, except sound, and modprobing my snd_soc_sst_broadwell fails - whereas in Ubuntu (main) 15.10, it works- , hence wanted to upgrade and came across this issue.)


Source: (StackOverflow)

What is the Ubuntu accessibility for blind people?

Are there specific configurations and packages that could help blind people to use Ubuntu?

Blind people do use computers, and Ubuntu should be accessible to everyone.

It would be interesting to have the testimony of a totally or partially blind person who uses Ubuntu sharing their experience.

(Using Ubuntu 16.04, but I'm open to other Linux distributions)


Source: (StackOverflow)

Ubuntu 16.04 LTS cannot suspend / fails on suspending

I have recently upgraded my desktop to Ubuntu 16.04. I had one problem with it before, which was that the Unity Launcher and status bar were missing. I solved this with this page. However, when I try to suspend my machine, the following occurs: The hard drive will save the last bits of data and will turn itself off. But the thing is: the computer itself is still turned on. This means I am stuck with no screen input, and it forces me to push the reset button on my computer case, as I can't take control of my pc anymore.

Can anyone help me with this?

Thanks in advance,

Reboot


Source: (StackOverflow)

Ubuntu 16.04 final not booting from stick: gfxboot.c32: not a COM32R image

The brand new 16.04 final does not boot from USB stick:

Missing parameter in configuration file. Keyword: path
gfxboot.c32: not a COM32R image
boot :

I made a boot stick with Startup Disk Creator on 14.04 LTS on a Lenovo laptop. I repeated this process on another computer (Gigabyte Brix) with a another 16.04 image (downloaded from another location) and a different USB stick. Also this computer didn't boot.

Upgrading from 14.04 LTS to 16.04 LTS is probably the most common scenario. How on earth did this get through beta testing??

Edit: in 14.04 LTS there was a similar issue: Ubuntu 14.04 LTS live USB boot error


Source: (StackOverflow)

16.04 Cannot install anything from Ubuntu Software center [duplicate]

This question already has an answer here:

Whenever I double click a deb file, it'd be opened in software center. However, when I click "install" button, it'd change to "installing" for a second but then turn back to "install" and nothing happens. It also says "This software comes from a 3rd party and may contain non-free components" at the bottom. I have enabled all the options in Software & Updates and also tried reinstalling software center but nothing helped.


Source: (StackOverflow)

Laptop freezes after connecting external monitor, since 16.04 update

I have a Zenbook UX303U with integrated Intel HD5000, and using an external monitor worked fine until I updated to Ubuntu 16.04LTS this weekend. Now, when I plug my second screen and then move the mouse cursor to the laptop's screen, the computer freezes: the mouse, touchpad and keyboard become unresponsive, I'm unable to access a terminal with Ctrl + Alt + F1 - 6 shortcut, and any open ssh connections to my laptop are lost. All I can do is hard reboot the computer.

Has anyone else experienced similar problems and figured out a solution?


Source: (StackOverflow)

How can I automatically fix W: Target Packages ... is configured multiple times?

I just installed Ubuntu Gnome 16.04. I told it to save my documents - which worked. Some software had to be reinstalled. Now when I run sudo apt-get update I see this:

W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (main/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (main/i18n/Translation-en_GB) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11 (main/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11-icons (main/dep11/icons-64x64.tar) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (restricted/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (restricted/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (restricted/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (restricted/i18n/Translation-en_GB) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (restricted/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11 (restricted/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11-icons (restricted/dep11/icons-64x64.tar) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (multiverse/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (multiverse/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (multiverse/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (multiverse/i18n/Translation-en_GB) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (multiverse/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11 (multiverse/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11-icons (multiverse/dep11/icons-64x64.tar) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: The repository 'http://extras.ubuntu.com/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: http://dl.google.com/linux/chrome/deb/dists/stable/Release.gpg: Signature by key 4CCA1EAF950CEE4AB83976DCA040830F7FAC5991 uses weak digest algorithm (SHA1)
W: http://repo.sinew.in/dists/stable/InRelease: Signature by key B6DA722E2E65721AF54B93966F7565879798C2FC uses weak digest algorithm (SHA1)
E: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/xenial/main/source/Sources  404  Not Found [IP: 91.189.92.152 80]
E: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found [IP: 91.189.92.152 80]
E: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/xenial/main/binary-i386/Packages  404  Not Found [IP: 91.189.92.152 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (main/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (main/i18n/Translation-en_GB) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11 (main/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11-icons (main/dep11/icons-64x64.tar) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (restricted/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (restricted/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (restricted/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (restricted/i18n/Translation-en_GB) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (restricted/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11 (restricted/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11-icons (restricted/dep11/icons-64x64.tar) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (multiverse/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (multiverse/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Packages (multiverse/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (multiverse/i18n/Translation-en_GB) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target Translations (multiverse/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11 (multiverse/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87
W: Target DEP-11-icons (multiverse/dep11/icons-64x64.tar) is configured multiple times in /etc/apt/sources.list:33 and /etc/apt/sources.list:87

Is there an automated way to fix this?


Source: (StackOverflow)

How do I modify "/sys/kernel/mm/transparent_hugepage/enabled"

I use mongodb 3.0 and I find a warning:

MongoDB shell version: 3.0.0
connecting to: test
Server has startup warnings: 
2015-03-13T16:28:29.405+0800 I CONTROL  [initandlisten] 
2015-03-13T16:28:29.406+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
2015-03-13T16:28:29.406+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2015-03-13T16:28:29.406+0800 I CONTROL  [initandlisten] 
2015-03-13T16:28:29.407+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2015-03-13T16:28:29.407+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2015-03-13T16:28:29.407+0800 I CONTROL  [initandlisten]

~# cat /sys/kernel/mm/transparent_hugepage/enabled
[always] madvise never

~# cat /sys/kernel/mm/transparent_hugepage/defrag
[always] madvise never

I try to use echo, but it's not permanent, after reboot it will be reset.

echo never > /sys/kernel/mm/transparent_hugepage/defrag

How do I modify /sys/kernel/mm/transparent_hugepage/enabled permanently?


Source: (StackOverflow)

What updates is 'Ubuntu Software' installing?

I have recently upgraded from 15.10 to 16.04LTS. Since the upgrade, I have still been prompted occasionally to update by 'Software Updater' which had been present in 15.10. Quite a few updates to Ubuntu core have been done this way.

In the last couple of days, when returning from suspend a popup has appeared in the same place as the wifi connected/disconnected information appears. This new popup told me that 'Important OS and application updates are ready..." before disappearing. Yet when I checked with the 'Software Updater' it told me that the software was up to date. Checking with the new 'Ubuntu Software' (update tab) told me that there were updates, so I clicked 'Install'. It didn't tell me what was being installed.

Why is there this different method of checking and why are the two giving different results?

How can I find out what the new Ubuntu Software did install ?

Edit 9th May

Again today the pop-up appeared. The 'Software Updater' showed the machine was up to date. The 'Ubuntu Software' app showed 1 update. On clicking the '1' icon it showed 1 update, namely: ubuntu-drivers-common 1:0.4.17.1. I clicked the 'Install' button and installed it.

I'm none the wiser as to why it is only shown as necessary by 1 app and not the other.


Source: (StackOverflow)

Can't view Wifi networks after upgrading to Ubuntu 16.04

I can't view any wifi networks after upgrading to Ubuntu 16.04 from 14.04. This issue also occurred when trying to upgrade to Ubuntu 15.10. This is what my network window looks like:

enter image description here

I have Broadcom enabled in the Software & Updates window: enter image description here

Also there is no option for Wifi in the dropdown menu in the top right. The screenshots are from Ubuntu GNOME, but it also doesn't work for standard Ubuntu. How can I enable wifi networks?

Output of lspci -knn | grep Net -A2:

07:00.0 Network controller [0280]: Broadcom Corporation BCM43142 802.11b/g/n [14e4:4365] (rev 01)
    Subsystem: XAVi Technologies Corp. BCM43142 802.11b/g/n [1b9a:3002]
    Kernel modules: bcma, wl

Output of sudo apt-get install bcmwl-kernel-source:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
bcmwl-kernel-source is already the newest version (6.30.223.248+bdcom-0ubuntu8).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

Output of sudo apt-get install --reinstall bcmwl-kernel-source:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not upgraded.
Need to get 0 B/1,515 kB of archives.
After this operation, 0 B of additional disk space will be used.
(Reading database ... 153417 files and directories currently installed.)
Preparing to unpack .../bcmwl-kernel-source_6.30.223.248+bdcom-0ubuntu8_amd64.deb ...
Removing all DKMS Modules
Done.
Unpacking bcmwl-kernel-source (6.30.223.248+bdcom-0ubuntu8) over (6.30.223.248+bdcom-0ubuntu8) ...
Setting up bcmwl-kernel-source (6.30.223.248+bdcom-0ubuntu8) ...
Loading new bcmwl-6.30.223.248+bdcom DKMS files...
Building only for 4.4.0-21-generic
Building for architecture x86_64
Building initial module for 4.4.0-21-generic
Done.

wl:
Running module version sanity check.
 - Original module
   - No original module exists within this kernel
 - Installation
   - Installing to /lib/modules/4.4.0-21-generic/updates/dkms/

depmod....

DKMS: install completed.
modprobe: ERROR: could not insert 'wl': Required key not available
update-initramfs: deferring update (trigger activated)
Processing triggers for initramfs-tools (0.122ubuntu8) ...
update-initramfs: Generating /boot/initrd.img-4.4.0-21-generic

Output of sudo modprobe wl:

modprobe: ERROR: could not insert 'wl': Required key not available

Source: (StackOverflow)