Sudo specific command with no password
How to run a specific program as root without a password prompt?
Packed images used as background don't show up when reopening the file I have seen a single (1) mention of View port background images disappearing when the .blend file is saved and reopened.  However...the answers are not relative to what I am experiencing.  I go through the trouble of setting up four images (top, side, front, back) and then pack these images using External Data &gt; Pack all into .blend and then I save the .blend.  I save the file, open it back up, and the background images are all gone. Open up properties panel, look to see background images check box is unchecked, click add image, and choosing the open drop-down arrow...the data paths still show the list of images (packed into a specific folder textures).  They are still there, the data set is intact.  Why is It that I have to set this up each and every time I open the file.  It seems like earlier versions &lt;2.76B saved the images and saved the file with the background images check box checked without the need to set this up each time the file is reopened.  This is getting very frustrating due to the fact that a few of the background images mus be set up using Blender's rotate, scale and move tools to align the background image up with the model I have already fabricated.  Thanks! Adjoint matrix eigenvalues and eigenvectors I just wanted to make sure that the following statement is true:  Let $A$ be a normal matrix with eigenvalues $\lambda_1,...,\lambda_n$ and eigenvectors $v_1,...,v_n$. Then $A^*$ has the same eigenvectors with eigenvalues $\bar{\lambda_1},..,\bar{\lambda_n}$, correct? How to find $\lim\limits_{x\to0}\frac{e^x-1-x}{x^2}$ without using l'Hopital's rule nor any series expansion? How To Delete This Red Box on My Screen? I was editing my mesh and I wanted to only see a part of my mesh, so I pressed alt+B to only show a selected area. However, I did ctrl+B and created a red rectangle on my screen (I don't know what it does). Does anybody know how to get it off? How to fix apt: Signature by key uses weak digest algorithm (SHA1)? Travelling with two different passports What is NDSolve`FEM`*? What factors influence the spring constant? For certain springs we have been taught that Hookes law, $F=-kx$ works. For such springs, what factors determine k. For instance, k is proportional to length. Can k be expressed in terms of dimensions, mass and other fundemental quantities, or is k a fundemental property of the spring itself? I am confused with the definition of non-parametric model after reading this link  and .   Originally I thought "parametric vs non-parametric" means if we have distribution assumptions on the model (similar to parametric or non-parametric hypothesis testing). But both of the resources claim "parametric vs non-parametric" can be determined by if number of parameters in the model is depending on number of rows in the data matrix.  For kernel density estimation (non-parametric) such a definition can be applied. But under this definition how can a neural network be a non-parametric model, as the number of parameters in the model is depending on the neural network structure and not on the number of rows in the data matrix?  What exactly is the difference between parametric and a non-parametric model? HTTP vs HTTPS performance Are there any major differences in performance between http and https?  I seem to recall reading that HTTPS can be a fifth as fast as HTTP.  Is this valid with the current generation webservers/browsers?  If so, are there any whitepapers to support it? Why did the snake wink at Harry at the zoo? This is mostly a memory question - I'm having a hard time remembering this and I can't read the book right now.  On the first book, a snake at the zoo winks at Harry. For the sake of the question, we'll assume that snakes can in fact wink.  I have a fuzzy memory here - I think that it winked before Harry had any kind of interaction with the snake (was this before or after Harry broke the glass?)  So, why did the snake wink at Harry? Given that they had not met ever before.  I suppose that the only reason it would wink at Harry would be because it knows Harry can communicate with it. But this would imply that snakes are capable of sensing such ability on wizards - is there (other) evidence that this is true? Travelling by bus Index entries duplicated for captions Proving the cross product matrix tranformation identity with an alternative solution I'm solving a problem from the book, Mathematics for 3D Game Programming and Computer Graphics, Third Edition, by Eric Lengley. The problem goes:  Let $N$ be the normal vector to a surface at a point $P$, and let $S$ and $T$ be tangent vectors at the point $P$ such that $S \times T = N$. Given an invertible 3 $\times$ 3 matrix $M$, show that $(MS) \times (MT) = (\text{det}M(M^{-1})^{T}(S \times T)$, supporting the fact that normals are correctly transformed by the inverse transpose of the matrix $M$.  The author provided a hint stating we can represent $(MS) \times (MT)$ as $$ (MS) \times (MT) = \begin{bmatrix} 0 &amp; -(MS)_{z} &amp; (MS)_{y} \\  (MS)_{z} &amp; 0 &amp; -(MS)_{x} \\  -(MS)_{y} &amp; (MS)_{x} &amp; 0  \end{bmatrix} MT $$ We then find a matrix $G$ such that $$ GU = \begin{bmatrix} 0 &amp; -(MS)_{z} &amp; (MS)_{y} \\  (MS)_{z} &amp; 0 &amp; -(MS)_{x} \\  -(MS)_{y} &amp; (MS)_{x} &amp; 0  \end{bmatrix} M $$ where $$ U = \begin{bmatrix} 0 &amp; -S_{z} &amp; S_{y} \\  S_{z} &amp; 0 &amp; -S_{x} \\  -S_{y} &amp; S_{x} &amp; 0  \end{bmatrix} $$ and show that $G = (\text{det}M)(M^{-1})^{T}$ to solve the problem. I am aware that there is an  to this problem, but I would like to solve it through the hints provided. Unfortunately, I am only able to go as far doing: $$ G = \begin{bmatrix} 0 &amp; -(MS)_{z} &amp; (MS)_{y} \\  (MS)_{z} &amp; 0 &amp; -(MS)_{x} \\  -(MS)_{y} &amp; (MS)_{x} &amp; 0  \end{bmatrix} M U^{-1} $$ At this point, I do not know how to proceed with showing that $G = (\text{det}M)(M^{-1})^{T}$. How would you proceed? I'd like to ask for hints on solving the problem. Free, open-source substitutes for Mendeley? At the end of ‘The Return of the King’, Bilbo, Frodo, Gandalf and others boarded a boat and left Middle-earth for Valinor.  Is there any canon explanation why they couldn’t just take the ring there in the first place and leave Middle-earth altogether? Would Sauron have gone after them? Couldn’t the elves living there safeguard it?  I do realize that without Frodo taking the ring to Mount Doom there would be no story at all, but I wonder whether or not there is any canon explanation for this. Subfields of $\mathbb{Q}(\sqrt{2},\sqrt{3})$ Suppose one doesn't know any Galois theory, but they are familiar with the basic theory of field extensions. Then how would one justify the following picture?    I'm pretty sure they're just saying these are the known subfields, and there could be more but they just write down those ones (which seems weird, which is why I'm asking). Or have they deduced that this is a comprehensive list of subfields just by using basic theory? This occurs on page 573 of Dummit and Foote's Abstract Algebra. Let f : A → B and g : B → C be bijections. Prove that g◦f : A → C is a bijection  Can someone show me the steps I should take to solve this problem? EL proposals / autocomplete / code assist in Facelets with Eclipse As seen in this video: (Skip to 5:53)  When a player is slain, they drop an Enchanting Table on top of their inventory.  How was this achieved and how can I build a system (using command blocks) that does that? Come to think of it, what happens to a player's location when he/she dies? Does it reset to the spawnpoint? Stay the same (where they died) until they respawn? Or becomes a null value until they respawn?