On what Stack Exchange site should I ask tech/platform questions like this one?
Right place to ask a "discussion" question (I'm setting up a blog, what should....)
How can I disable cloud-init? I have a fully-configured instance and an image from that for an autoscaling group. When autoscaling new instances from this image, it calls cloud-init. cloud-init changes the hostname and breaks fstab.  I want to prevent cloud-init from starting on instance launch. Log4Net "Could not find schema information" messages Casting nines and elevens in other bases (radix) and doing check sums for binary What does "65" mean? K-2SO beats up the troopers easily. Up in the sky, the bombers are preparing to attack. Just as they start the attack run, TIE fighters come in from the shield and swarm the rebel fleet.  JON VANDER (GOLD LEADER): Red Leader, this is Gold Leader, we’re starting our attack run on the  shield gate. Keep it tight and watch out for those towers. GOLD PILOT: More fighters. Form up, at 65.  What does &quot;65&quot; mean? Is my Ubuntu vulnerable to SambaCry? I read these two threads:         And I got a little bit worried, is my Ubuntu machine safe? Or am I vulnerable to this vulnerability?  The second article mentioned that:     The flaw actually resided in the way Samba handled shared libraries.   The other thing that they say is all versions from versions 3.5.0 onwards since 2010 are vulnerable.     At that time, nearly 485,000 Samba-enabled computers were found to be exposed on the Internet, and researchers predicted that the SambaCry-based attacks also have potential to spread just like WannaCry ransomware widely.   .   I don't have a samba server however I've got samba-libs package installed.  What, if anything, should I do?  I'm running Ubuntu 16.04. Is the Schrödinger equation derived or postulated? I'm an undergraduate mathematics student trying to understand some quantum mechanics, but I'm having a hard time understanding what is the status of the Schrödinger equation.  In some places I've read that it's just a postulate. At least, that's how I interpret e.g. the following quote:     Where did we get that (equation) from? Nowhere. It is not possible to derive it from anything you know. It came out of the mind of Schrödinger.    -- Richard Feynman   (from the Wikipedia entry on the Schrödinger equation)  However, some places seem to derive the Schrödinger equation: just search for "derivation of Schrödinger equation" in google.  This motivates the question in the title: Is the Schrödinger equation derived or postulated? If it is derived, then just how is it derived, and from what principles? If it is postulated, then it surely came out of somewhere. Something like "in these special cases it can be derived, and then we postulate it works in general". Or maybe not?  Thanks in advance, and please bear with my physical ignorance. If A is invertible, prove that $\lambda \neq 0$, and $\vec{v}$ is also an eigenvector for $A^{-1}$, what is the corresponding eigenvalue? If A is invertible, prove that $\lambda \neq 0$, and $\vec{v}$ is also an eigenvector for $A^{-1}$, what is the corresponding eigenvalue?  I don't really know where to start with this one. I know that $p(0)=det(0*I_{n}-A)=det(-A)=(-1)^{n}*det(A)$, thus if both $p(0)$ and $det(0) = 0$ then $0$ is an eigenvalue of A and A is not invertible. If neither are $0$, then $0$ is not an eigenvalue of A and thus A is invertible. I'm unsure of how to use this information to prove $\vec{v}$ is also an eigenvector for $A^{-1}$ and how to find a corresponding eigenvalue. How can I remove a trailing newline? As a 8th grader I am still a newbie at science and I have problems understanding the forces that I can not imagine and one of these "forces" is the moment.  We are told that,  $$\text{moment}= Nm$$ but how can a certain force (i.e. $N$) be applied when there is $m$? How does it depend on the length of the considered object?  And how can 1 moment be defined on the basis of that representation?  And what would be the effect if the moment value is increased by the newton part as opposed to the effect when the value is increased by the length part.  Or is the result the same in both cases? Let the function $f(x)$ be differentiable  and $f'(x)$ be continuous in $\left(-\infty,\infty \right)$ with $f'(2)=14$ then evaluate the limit  $$\lim_{x\to 0}\frac{f(2+\sin x)-f(2+x\cos x)}{x-\sin x}$$  My attempt:  $\lim_{x\to 0}\frac{f(2+\sin x)-f(2+x\cos x)}{x-\sin x}$  $\lim_{x\to 0}\left(\frac{f(2+\sin x)-f(2+x\cos x)}{\sin x-x\cos x}\right)$ $\frac{\sin x-x\cos x}{x-\sin x}$$=\left(f'(2)\right)(2)=28$  Is the method used here correct Proof of greatest integer theorem: floor function is well-defined I have to prove that  $$\forall x \in \mathbb{R},\exists !\,n \in \mathbb{Z} \text{ s.t. }n \leq x &lt; n+1\;.$$  where $\exists !\,n $ means there exists a unique (exactly one) $n$. I'm done with proving that there are at least one integers for the solution. I couldn't prove the &quot;uniqueness&quot; of the solution, and so I looked up the internet, and here's what I found:  Let $\hspace{2mm}n,m \in \mathbb{Z} \text{ s.t. }n \leq x &lt; n+1$ and $m \leq x &lt; m+1$. Since $n \leq x \text{ and } -(m+1) &lt; -x$, by adding both, $n + (-m-1) &lt; (x-x) = 0$. And (some steps here) likewise, $(x-x) &lt; n+m+1$.  Now, can I add up inequalities like that, even when the book is about real analysis (and in which assumptions are supposed to be really minimal)? Or should I also prove those addition of inequalities? Thank you :D Where does gravitational waves' energy go? Following the measurement of gravitational waves, many sources described them and explained they carry energy away. What I don't get is how this energy will get transfered back to anything else.  If the fabric of space-time itself is vibrating, it would seem to be in impossible for any physical object to gain this energy.    What am I missing?  How would one hypothetically get energy out of gravitational waves?  If impossible, does the universe end up with nothing but GW? Are aerosol cans allowed and safe, in checked luggage? Is there a function to round a float in C or do I need to write my own?       float conver = 45.592346543;   I would like to round the actual value to one decimal place, conver = 45.6. The $n$ complex $n$th roots of a complex number $z$ In the DC Comics Universe, What Happens to Earthlings Under a Red Sun? I know in the earliest versions of Superman, his powers weren't from the yellow sun, but that was changed and, in general (at least as I understand it), Superman's powers are because he was native to a world with a red sun and now he's under a yellow sun.  What happens to an Earthling or other native to a yellow sun planet when near a red sun?  And what if the sun is blue?  Or a brown dwarf?  Please note: I'm asking about a red sun, not about living on Krypton.  Okay, that's heavy gravity, but it's not the only planet under a red sun.  (But, still the point about whether yellow sun natives would have super powers would come into play there, wouldn't it?) Script access to tangent and bitangent, per face: how? Suppose you have a mesh; you go into Edit mode,  set Transform Orientation to Normal,  show 3D manipulator widget, Pivot Point = Active Element, face select mode, and then you select any one face: immediately you will see a blue arrow representing the face normal, and also a red and a green arrow representing the face's tangent and bitangent.  What is the most straightforward way to refer  to said tangent and bitangent vectors from a Python script? The API documentation confuses me with loops and uv's, yet, clearly, Blender assigns a tangent and bitangent to each face without hesitation! Please provide me with the guidance to install oracle 11gr2 on Ubuntu 14.04. Microsoft recommends using Rowversion over timestamp, but I can not find "rowversion" data type inside my sql server 2008 R2 Microsoft  mentioned that we should use the rowversion data type over Timestamps. Now inside my SQL Server 2008 R2, I want to create a column with the Rowversion data type. But in my SQL Server 2008 R2 Management Studio, I cannot find such a data type:  Also when I tried altering existing column named timestamp which is of type timestamp using this statement: ALTER TABLE [SkillManagement].[dbo].[Customer] ALTER COLUMN timestamp rowversion   I get this error: Msg 4927, Level 16, State 1, Line 1 Cannot alter column 'timestamp' to be data type timestamp  Can anyone advise? EDIT How to capture text from the operating system in a practical and simple way? Sometimes we can't select the text to copy &amp; paste, such as dialog boxes.  Sometimes it's just not practical, such as 100 files inside a folder.  Is there any practical and simple way to capture those text from the system into a text file?  I'd wish to know both in OS X and Windows. Maybe it just can't be done today...