I have a HP Elite book 840G3 laptop with Windows installed in the primary drive and Ubuntu installed in the second drive. What is to be done to get to pick the operating system option on starting up.   Right now I press Esc on startup and pick the needed drive from the BIOS Boot Menu screen.
I have installed Ubuntu 15.10 alongside Windows 10 with UEFI. To install Ubuntu, I chose the option install alongside Windows 10 or something similar to this. Then I created a new partition for Ubuntu and installed it. After installation, the boot menu did not show up. Initially I thought Ubuntu has not been installed, but when I plugged in the USB drive and wanted to install Ubuntu I saw an option of reinstalling Ubuntu on my machine. So, I found out that Ubuntu is installed. Pressing F8 and F12 also does not help. Can anyone help me bring up the GRUB boot menu? In Windows, I also entered the command bcdedit /set {bootmgr} path \EFI\ubuntu\grubx64.efi in cmd, but still the boot menu does not show up.  Reply (Himanshu) : Just boot in bios and, if you can, add boot option with name say ubuntu and path EFI/ubuntu/shimx64.efi. No need for live PCB or anything. Move the boot option to top. This is for dell GUI bios but I assume it works for all. Or you may want to see  or , where you can enable Windows Boot Loader for one boot or forever as you wish, and boot Ubuntu from it. If you want now, you can use the installed Ubuntu terminal to use the commands update-grub to use GRUB instead. (Not enough reputation to answer properly btw.)
During the First Wizarding War, why didn't Dumbledore just hunt Voldemort down, as he had done with Grindelwald?  By 'hunting down', I mean finding, defeating and imprisoning him, exactly as in Gridelwald's case, and not, say killing him, something which Dumbledore would not do, as the answers to a previous question (as to him not hunting down Death Eaters) show.  Dumbledore knew that Voldemort had delved into the Dark Arts deeper than anyone else in history and hence "had powers he will never have". But he must have also known well that he could have defeated Voldemort at a direct confrontation, given that he had defeated Grindelwald earlier even against the Elder Wand, and now had that same wand at his disposal. He is seen confident about this throughout the series.  At the Battle of the Department of Mysteries, he did not go beyond outweighing Voldemort and forcing him to flee, probably because, by then, he had reasons to suspect that there was more to Voldemort's survival than his physical body, and thus, destroying that body which had Harry's blood without permanently disposing him off would not have been wise.  But why did he not do that at the First Wizarding War? Is it just that they could not track him down, or did he suspect even then that Voldemort had more sinister things about his soul? is there any canon confirmation of the latter suspicion? Over the course of time here on TSE, I have observed individuals whose pattern of visa applications is best described as ''...     serial refusals - Two or more consecutive visa refusals issued by the same regime to the same person. Commonly for the same, or nearly the same, reasons. In some visa regimes Serial refusals can have a cumulative effect wherein the applicant's credibility is increasingly eroded, especially when the application pattern suggests a secondary agenda.   A common thread appears to be the need to visit the destination country (especially Schengen, the USA, or the UK) with a special sense of urgency. Also common in these cases are the following types of questions...   Should I just reapply once again? What are my chances? What can I do to improve my odds in the future? Can I somehow address the previous refusals to avoid them being a burden on all future applications? How can I break the pattern?      NB: This question is intended as a canonical about serial refusals. I have never been personally denied a visa. I am using this IC in boost converter configuration :   It steps up the voltage from 16.5V to 23V.   It drives a load current of 270mA.  I need to calculate the input current of the converter.   I understand that output power/input power is efficiency.   Since I know the output power, can I take the efficiency value from the graph 21 of the attached datasheet (86.8% approx - obtained from fig 21 graph) and find the input power?   With the input power, and since I know the input voltage, I can calculate the input current.   Is this the right way?   And I want to check if all the components at the output of the IC are properly rated.   Which parameters and components should I check and how to check?    Sorry for the poor image quality. The two transistors are taken from the SWE pin. Where can I find a free, very quick, and reliable implementation of FFT in C#?  That can be used in a product? Or are there any restrictions? On sites with new responsive theme, word wrap on long titles breaks in the middle of a word For sites that have the new responsive theme enabled, where the "Ask Question" button is in line with the question title on question pages, the word wrap on long titles is not working correctly.  It will break a word across two lines.  Here is an  from Personal Finance and Money:  Maximum width, left nav hidden:   Narrow width:   This is also happening on beta sites.  Here is an  on Sports:    These screenshots were all taken on Firefox, but I am seeing the same problems in Chrome and Internet Explorer.  One more example: Can you find all classes in a package using reflection? Is it possible to find all classes or interfaces in a given package? (Quickly looking at e.g. , it would seem like no.) Cannot change lock screen background on Ubuntu 18.04 Before you mark the question as a duplicate, I read all of the posts regarding this, but nothing helped me. I'd like to change the background picture of the lock screen.    I changed the ubuntu.css and gdm3.css accordingly to   #lockDialogGroup {   background: #000000 url(file:///usr/share/wallpapers/minimalistic-gray_00323985.jpg);   background-repeat: no-repeat;   background-size: cover;   background-position: center; }   Which results in a change of the Background of the log in screen, not the lock screen. When I press super + L the screen containing time has the correct background. When I swipe it up to tipe in my password, the purple Ubuntu screen still appears. If I click to change the user, the log in screen appears with the right background. I have the same background picture enabled in gnome tweaks for desktop background and lock screen.   I'm running Ubuntu 18.04 GNOME on a TuXedo Laptop. And I use Communitheme - maybe thats the problem?  Any ideas why it doesn't work? (I rebooted multiple times, so that's not the problem.)  EDIT: The output of sudo nano /usr/share/gnome-shell/modes/ubuntu.json is  {     "parentMode": "user",     "stylesheetName": "ubuntu.css",     "enabledExtensions": ["ubuntu-dock@ubuntu.com", "ubuntu-appindicators@ubuntu.com"] } How to initialize all members of an array to the same value? How can a piece of A4 paper be folded in exactly three equal parts? This is something that always annoys me when putting an A4 letter in a oblong envelope: one has to estimate where to put the creases when folding the letter. I normally start from the bottom and on eye estimate where to fold. Then I turn the letter over and fold bottom to top. Most of the time ending up with three different areas. There must be a way to do this exactly, without using any tools (ruler, etc.). Badge Notification Repeats Limiting floats to two decimal points How can I check if a program exists from a Bash script? I typically have two needs:  Scenario A. Change a single PDF page.  In this case I have a PDF but not the original source file used to create the PDF. I don't want to try to recreate the document from scratch. I'd like to open the PDF and change a few things. A good example of this scenario: I was responsible for planning a big event at a campground site, I had a PDF of the site. I wanted to start with that document, highlight some parts, add some labels, remove some parts that weren't relevant.   or   Scenario B. Combine PDFs or extract page(s) from a PDF  This scenario usually arises because I want a single PDF deliverable that is made up of parts that are best created in different programs. In this case I have the source files for all the documents but they don't play well enough together to easily create a single PDF deliverable. For part of it, I may want to use Libre Office Writer. For another page I may want to use Gimp. Still another page I may use Libre Office Calc. I could use Writer as the master document and embed images or the Calc object into that, but for ultimate control, you can't beat separate PDF documents that are then combined.  What are the best tools / processes for editing PDFs in Ubuntu? If the $n^{th}$ partial sum of a series $\sum a_n$ is $S_n = \frac{n-1}{n+1}$, find $a_n$ and the sum. If the $n^{th}$ partial sum of a series $\sum a_n$ is $S_n = \dfrac{n-1}{n+1}$, find $a_n$ and the sum.  By definition,  the sum of the series is the $\lim n\to\infty$ of it's $n^{th}$ partial sum.  $$\text{ Sum = } \lim_{n\to\infty} = \dfrac{n-1}{n+1} = 1$$  I am asked to find $a_n$. How do I do this? What is the procedure? How long should it take to refresh a Developer Sandbox? I refreshed a Developer Sandbox, and almost 24 hours it is still "pending". Is this normal? Are there any actions I can take to speed up the process? When I created the Sandbox it took barely more than 10 minutes to create.  Thanks, Adrian Rigid Simulation freezes at frame 250 Combining two covariance matrices I am having a hard time with the following real analysis qual problem.  Any help would be awesome.  Suppose that $f \in L^p(\mathbb{R})$, where $1\leq p&lt; + \infty$. Let $T_r(f)(t)=f(t−r)$. Show that $\lim_{r \to 0} \|T_rf−f\|_{L_p} =0$, that is $$ \lim_{r\to 0} \left( \int_{\mathbb R} |f(t-r) - f(t)|^p \mathrm d t\right)^{1/p} =0.$$ chown -R root.root / So I was working and there was a directory that I was periodically changing to my user in  a root terminal so that I could open the files in text editors, but I accidentally pressed / instead of . and this was the command I put out:  chown -R emil.emil /   Then immediately panicked ^C and put in another command, as I thought I could always change back the files I needed to access:  chown -R root.root /   So now I can't do su from emil to even try to fix this, as I'm getting permission denied error. I'm on Ubuntu could someone tell me if there is a way I could fix this, without absolutely reinstalling the whole thing.  TIP  If you are trying to get root access, and are getting this permission denied error when using su try this command:  gksu gnome-terminal   It will prompt you for the root password and open a new root terminal for some reason this works and gives me root access, when su doesn't. The parametric equation  $$\begin{align*} x(t) &amp;= \cos t\\ y(t) &amp;= \sin t \end{align*}$$  traces the unit circle centered at the origin ($x^2+y^2=1$).   Similarly,   $$\begin{align*} x(t) &amp;= \cosh t\\ y(t) &amp;= \sinh t \end{align*}$$  draws the right part of a regular hyperbola ($x^2-y^2=1$).  The hyperbolic trigonometric functions are very similar to the standard trigonometric function.  Do similar functions exist that trace parabolas (because it is another conic section) when set up as parametric equations like the above functions?  If so, are they also similar to the standard and hyperbolic trigonometric functions?