I have installed Windows along with Ubuntu 16.04. After installed Windows, I can't navigate to my Ubuntu installation.  I tried with live repair, booted Ubuntu 16.04 on my flash drive and tried to update grub according to  but I'm getting this error:
I installed Windows 7, which ate Ubuntu's boot file. When starting up the computer, it now goes straight to Windows, without giving me the option of booting Ubuntu.   How can I get Ubuntu back?
Is it possible to create an  shader in Cycles? Specifically for something like , , , etc.. Spaces in variable assignments in shell scripts How many non-negative integer solutions does the equation $3x + y + z = 24$ have? How can I find non-ASCII characters in MySQL? I'm working with a MySQL database that has some data imported from . The data contains non- characters (em dashes, etc.) as well as hidden carriage returns or line feeds. Is there a way to find these records using MySQL? Plotting two variables as lines using ggplot2 on the same graph Can I use Stack Exchange logos on a t-shirt or other apparel? I happened to notice while on the Super User site that one user's picture shows him wearing a shirt with the Super User logo on it. Interested, I wanted to find out where he got it from. Looking through old questions on Meta, I found out that there used to be a shop.stackexchange.com site that sold Stack Exchange gear. Unfortunately, they no longer sell any merchandise.  Is there any site where I can purchase a Stack Exchange site shirt/hat/etc.? If not, could I create a shirt/hat/etc. myself with one of the sites' logos on it? If so, where can I locate the logos in their largest size? How would you handle different aspect ratios in a 2d platformer? Determining a matrix from its characteristic polynomial What's the full-form & significance of USS & ISS prefixes in name of Star Trek starships? In the Star Trek normal universe, almost all of Starfleet's starships were named with the prefix USS: Count from . Some popular ones: USS Enterprise - series, USS Stargazer, USS Exeter, USS Defiant, USS Excelsior, USS Voyager, USS Titan, USS Reliant, USS Equinox, USS Grissom, USS Relativity, etc.  In the mirror universe, Starfleet's starships were named with the prefix ISS. We don't have a big list, but we do see these: ISS Enterprise NX-01, ISS Enterprise NCC-1701, ISS Avenger.  What's the full form of USS &amp; ISS in Star Trek canon?  In the real world, the US Navy uses USS in ship names, which is reasonable as "United States Ship", but why is it used in Star Trek canon (in which there's no US to control starships)?  In the mirror universe, USS is replaced with ISS. Why? Does ISS have a meaning opposite from that of USS? My English teacher feels very strongly that exact same is redundant and therefore incorrect. I disagree with her.  She feels that exact should be used in place of exact same, but I have rarely heard someone use exact by itself. For example:     I have the exact same shirt   I have the exact shirt   In the same manner, I believe that she shuns exactly the same as well.  What support is there (if any) supporting the use of exact same or exactly the same? What proof can I provide for using exact same when challenged? The optical density of a medium is quantified by its refractive index $n$. Does it have any correlation with the mass/number density of the medium? In other words is an optically denser medium must have a greater mass density compared to an optically rarer medium? I need to match a space character in a PHP regular expression. Anyone got any ideas?  I mean like "gavin schulz", the space in between the two words. I am using a regular expression to make sure that I only allow letters, number and a space. But I'm not sure how to find the space. This is what I have right now:  $newtag = preg_replace("/[^a-zA-Z0-9s|]/", "", $tag); increasing impedance of headphones I have headphones with differential input and impedance of 8 ohms. I need to drive this headphone with some DAC with built in headphone driver (Currently I have chosen ADAU1772). DAC's datasheet mentions that the minimum impedance of headphones it supports is 16 ohms. Can I increase impedance of my headphones so that I can drive them through this chip? What will happen if I drive this 8 ohm headphone through a chip supporting minimum impedance of 16 Ohms? Render shadows over a transparent background in cycles I'm trying to make a logo that will be on the header of a website. What I'd like to achieve, and the reason I'm using Blender, is the projected shadows on the background looking perfectly real (as opposed to doing a drop-shadow in Photoshop).  The only thing is, the background has to be transparent because the website might use different background colors / gradients that make it impossible to match with the exported 3D background.  I made this dummy file (not the real logo... duh!):    If I use the file as is, the grey borders of the image will be impossible to match with the website's background color.  Here what I want:    So obviously, I tried masking the plane, which made the shadows disappear. I tried having a plane set to glass, which didn't work either.  And I looked around for a similar question, but didn't find one.   I am not trying to render , or a . I've seen  which has a very difficult solution to this problem, and  that is very similar but in Blender Internal.  is similar too but has never been solved. I'm only a beginner at Compositor, and I'm trying to learn more any chance I get, so any solution in Compositor is welcome if detailed enough. Although if there's a simpler or faster way, it's welcome too!  .blend file: Prove $| \sum_{i \leq n} \frac{\mu(i)}{i} | \leq 1$ So I am trying to prove the above stated formula. I am completely new to number theory so I thank you in advance for baring with me. I start off by using the definition:  $\frac{\phi(n)}{n} = \sum_{d|n} \frac{\mu(d)}{d}$  Where $\phi$ is Eulers function, and $\mu$ is the Mobius mu function. From here, I use the Mobius inversion formula to give:  $\frac{\mu(n)}{n} = \sum_{d|n}d\frac{\phi(\frac{n}{d})}{n}\mu(d)$  Now summing $n$ up to $x$:  $\sum_{n \leq x}\frac{\mu(n)}{n} = \sum_{n \leq x}\sum_{d|n}d\frac{\phi(\frac{n}{d})}{n}\mu(d)$  Now I'm not fully sure on how I can rearrange things inside the two summations on the right hand side, so leaving things as they are; using that $\sum_{d|n} \mu(d) = 1$, if and only if $n =1$. Hence:  $\sum_{n \leq x}\frac{\mu(n)}{n} = \sum_{d|1}d\phi(\frac{1}{d})\mu(d)$  Thus $d=1$. Subbing this in:  $\sum_{n \leq x}\frac{\mu(n)}{n} = \phi(1) = 1$  I am not sure what I have missed (or done wrong) as to have an equality and not a triangle relation. Any suggestions or ideas would be greatly appreciated How to make password-less login work I generated a key and copied it to my target:  ssh-keygen ssh-copy-id username@hostname   I left the the location of the key as default and did not set any passphrase.  For a small while after that, I was able to ssh username@hostname without being prompted for a password, and then it stopped working for some reason. Do inequalities hold under differentiation? If I have the inequality $f \leq g$, does this imply $f'\leq g'$?  The reason I am asking is because I am using this fact to prove a question with Taylor theorem. Command to display and execute code (math formulae) Similar to  I would like to have a command to display and execute code. The code should be displayed with the listings package.  For example something like  \documentclass{scrartcl} \usepackage{amsmath,listings} \newcommand*{\codeExample}[1]{Code: \lstinline!\string{#1}! yields #1} \begin{document}   \codeExample{$\lVert a\rVert$} \end{document}   should for best of cases display $\lVert a \rVert$ as verbatim (\lstinline!...!) code and after that the rendered math code. Is something like that possible? The code above yields several mistakes. I think I miss something to avoid #1 being tokenised? How can I make all text the same font size (normal text, footnotes, acknowledgements etc.)? I have to submit a manuscript to a journal, and I just realized that they want every single part of the paper to be in 12 pt font. This includes tables text, footnotes, acknowledgements etc. Is there a way to force all text to be the same size? At this point, I am unclear as to how to handle encounter XP. Does each surviving party member receive a proportional share, or the full amount? That is, assume a 4-character party had completed an encounter worth 400 XP. Would each party member receive 100 XP, or 400 XP?