I have 17.10 installed in a dual-boot with Windows 7 pro on a home built AMD machine.  When I log in, it tells me that 17.10 is no longer supported and I should upgrade to 18.04LTS.  When I click "upgrade" it asks for authentication, which I provide.  Then nothing happens.  If I click the software updater (icon with tools) it searches, then says it cannot connect to the repository and to check my internet connection, which is working fine at about 500 Mb hardwired to Comcast.  Then it again gives me the message saying I should upgrade...  Tried this 3 times with no results.  What can you suggest?  I really don't want to screw up the dual boot installation.
Recently I have installed an older version of Ubuntu on my old machine. Whenever I try to install any software, I get an error saying it couldn't be found:  $ sudo apt-get install vlc Reading package lists... Done                Building dependency tree        Reading state information... Done     E: Couldn't find package vlc
Homebrew putty installation does not make the putty command recognisable I would like to instal  with use of Homebrew. I'm performing the following command:  brew install putty   which gives the seemingly correct output:  ==&gt; Downloading https://homebrew.bintray.com/bottles/putty-0.67.el_capitan.bottle.tar.gz Already downloaded: /Users/thisuser/Library/Caches/Homebrew/putty-0.67.el_capitan.bottle.tar.gz ==&gt; Pouring putty-0.67.el_capitan.bottle.tar.gz 🍺  /usr/local/Cellar/putty/0.67: 11 files, 1.5M   However, the putty command is not recognised:  thisuser-541/41:~$ putty -bash: putty: command not found I host am ExpressionEngine based website on a single Amazon EC2 instance in the US East (Virginia) region. I use Ubuntu.    The website allows members to post their content, and displays it for other members and for users who are not logged in.   Goal: I need to begin serving the same website across the globe, equally fast to Hong Kong, New York, and Los Angeles.   I considered two solutions:  1.Setting up three separate EC2 instances for three regions: Virginia, Oregon, and Singapore. Use Amazon Rot53 Geo Location to direct traffic to instances based on the browser's IP address.   Pro: the website will load fast for the region.   Contra: these will be essentially three separate websites. Unless I am mistaken?   Setting up one instance in a region equally remote from all three locations: (Ireliand), and boost the server to the highest performance available.    Pro: It will be the same website for all regions.   Contra: it will cost a lot to make it fast enough.   My challenges:   a) I do not know a way to sync server settings, database, and content between multiple Ubuntu instances in real time. If a knowledgeable person could explain to me how to do that, I would be most grateful.   b) I am not thoroughly familiar with all Amazon AWS resources. Does AWS has a built-in method that would allow me to achieve my goal of serving a single PHP / MySQL based membership website across the globe equally fast in all three chosen locations? Where are the necessary places to be appended with % to remove unwanted spaces? I have  experience where empty spaces cause unwanted effects. It is not easy to trace the cause of these unwanted effects. In order to eliminate any doubt, I often overuse % as follows.   \usepackage% [% left=3cm, right=3cm% ]% {geometry}   or  \newcommand{\mycommand}% {% This is my command.% }   I got an extreme example that will break what Leo Liu said     In fact, only spaces which would be   output have to be removed by comment.   The following code does not produce output, but we cannot remove the % and leave a blank line between two elements of a list below.  \newpsstyle{gridstyle} { gridwidth=0.4pt, % griddots=0 }   Shortly speaking, where are the necessary places to be appended with % to remove unwanted spaces? How can I use sed to replace a multi-line string? I've noticed that, if I add \n to a pattern for substituting using sed, it does not match. Example:  $ cat &gt; alpha.txt This is a test Please do not be alarmed  $ sed -i'.original' 's/a test\nPlease do not/not a test\nBe/' alpha.txt  $ diff alpha.txt{,.original}  $ # No differences printed out   How can I get this to work? Linux Debian codenames I've got a few, quite silly, non-technical questions about giving  to  releases.  Each Debian release has its unique codename, which is (so far) a characters' name from  movies by .  Here is list of all assigned codenames so far:   release 1.1 is  (Buzz Lightyear) - the spaceman, release 1.2 is  - the tyrannosaurus, release 1.3.x is  (Bo Peep) - the girl who took care of the sheep, release 2.0 is  - the piggy bank, release 2.1 is  (Slinky Dog) - the toy dog, release 2.2 is  - Mr. Potato, release 3.0 is  -  the cowboy, release 3.1 is  - the sergeant of the Green Plastic Army Men, release 4.0 is  - the toy blackboard (Etch-a-Sketch), release 5.0 is  - the toy binoculars, release 6.0 is  - the name for the three-eyed aliens, release 7.0 is  - the name of the rubber toy penguin with a red bow tie, release 8.0 is  - the name of the yodelling cowgirl, release 9.0 is  - a purple rubbery octopus toy at , release 10.0 is  - 's pet dachshund (currently ).   List of upcoming major Debian releases' codenames after :   release 11.0 is  - 's horse (currently ), release 12.0 is  - intelligent worm toy with a built-in flashlight.   There are also:   special codename  () which is symbolic link to codename which is currently unstable,  which is symbolic link to codename which is currently stable,  which is symbolic link to codename which is currently testing.   The list of Toy Story  is quite  but at some time, there will be no more characters' names to assign.  My questions are:   What codenames will be assigned if we run out of characters' names? Who decides what is codename of next release (please don't answer ambiguously like: 'community')? How many releases' names are planned ahead?   BTW: Interesting quote from :     The  of using Toy Story names was  by  who   was, at the time, the Debian Project Leader and was working also at   , the company that produced the movies.     by  (: ). What are the proper uses of:   static_cast dynamic_cast const_cast reinterpret_cast C-style cast (type)value Function-style cast type(value)   How does one decide which to use in which specific cases? I`m using the Newton-Raphson method for obtaining MLE for parameters for maximizing my objective function. At each iteration, I want to check that is the Hessian matrix negative definite or not and I see the Hessian matrix is not negative definite at some iterations. So, I want to use the Fisher scoring algorithm ( of derivation) In this situation, the Fisher information matrix is indefinite!! Is it possible? What are the reasons for this? Are the second-order derivatives wrong? Or are values of expectations incorrect? Let $A \subset B$ be a finite ring extension. Fix a ring homomorphism $\nu : A \to \Omega$, where $\Omega$ is an algebraically closed field.   I want to show there exists a non-zero homomorphism $v : B \to \Omega$ of $A$-modules.  I want show that the space $V$ of all the homomorphisms $v$ in (i) is a non-zero finite dimensional vector space over $\Omega$. Show that the algebra $B$ acts on this space. Show that eigenvectors of this action correspond to homomorphisms of algebras $\lambda : B \to \Omega$ that extend the homomorphism $\nu$. Deduce that the set of such homomorphisms $\lambda : B \to \Omega$ is finite and non-empty.    We can assume that $B = Ab_1 + ... + Ab_n$ where $b_1,...,b_n \in B$. The chose $v(b_i)=\omega_i \in \Omega-\{0\}$ and then define $$ v( a_1 b_1 + ... + a_n b_n ) = \nu(a_1) v(b_1) + ... + \nu(a_n) v_n = \nu(a_1) \omega_1 + ... + \nu(a_n) \omega_n \ .$$ This is an $A$-module homomorphism. Am I correct? For the second part, that $V$ is not-zero follows from the first part. That it is finite dimensional follows from the fact that $v_i(b_j)=\delta_{i,j}$ (Kronecker's delta) with $i=1,...,n$ spans $V$ and hence $\dim V \le n &lt; \infty$. I define the action of $B$ over $V$ to be $$b \bullet v = \left( x \mapsto v(b)v(x) \right) \mbox{  for all } b,x \in B \ .$$ This seems to be the natural action to define. Am I correct? However, I haven't managed to solved the rest (the eigenvector stuff and the relation to $\nu$). When to use Stateful session bean over Stateless session bean? Why is there free space at the end of NTFS Partitioned Drives? I've been wondering this for a while, why is there free space at the end of a drive that was formatted to NTFS in windows?  You can only see the unallocated space in Linux. So why is it there? Does it serve a purpose? Integrating $\int^0_\pi \frac{x \sin x}{1+\cos^2 x}$ Residue fields of schemes of finite type (over $\mathbb{Z}$) Suppose $X$ is a scheme of finite type over $\mathbb Z$. I want to prove that:  (1) The residue fields of closed points of $X$ are finite;  (2) For a given $q=p^n$ with $p$ prime, there is only a finite number of closed points of $X$ whose residue field is $\mathbb F_q$.  For (1), I see that one has to use some form of Nullstellensatz. First, we suppose $X=\operatorname{Spec}(A)$ affine, and $A=\mathbb{Z}[X_1,...,X_n]/I$. We need to show that if $m$ a maximal ideal of $A$, then $A/m$ is finite. Note $p=\mathbb Z\cap m$. If $p$ is maximal, we get that $A/m$ is of finite type over $\mathbb F_p$ thus a finite extension by Nullstellensatz and we are done. But $p$ could be the $(0)$ ideal in which case I neither conclude nor get a contradiction.  For (2), we can again argue locally, so we need to show that $A$ contains only a finite number of maximal ideals $m$ with $A/m$ of fixed cardinality $q=p^n$. I get an impression that to count these ideals its the same as to count the number of automorphisms of $\mathbb{F}_{q}$ which fix $\mathbb F_p$, but the corrspondence is not bijective, so we only get an upper bound which is enough. Is this idea correct? Edit answer draft is broken The Edit Answer Draft button is broken.    Press Back with text in an answer box. The Edit answer draft bar does not appear.     Seems like an onBackPressed() issue.  Also:   Press ← with text in the answer box The bar appears. Click the bar The answer box is blank.   Seems like the answer isn't properly carried between the Fragments.  Either way, you lost everything you wrote.  Can somebody test this? And especially without a confirm dialog, it is a brush of the finger to lose a long post of code or something.   I hope this report will help because I like the app (I'd say 4/5 stars) but the bugs are preventing a solid 5 stars.   Stack Exchange 1.0.73 Samsung Galaxy S II Skyrocket I727 Android 4.1.2 Preposition confusion - Do you learn somthing 'at' school OR 'in' school? I know that we use the preposition at to describe a place. I learned French at school is one of the examples I can think of.   I came across two examples that use the preposition 'in' with 'schools' in the context of 'learning'.   Example #1 from the  website:      Eleven things that you will never learn in school.   Example #2 from      Do you think the skills you learn in school will help you get the job you want?   The use that I had in my mind is here on      Should Parents Control What Kids Learn at School? Adding values to a C# array Probably a really simple one this - I'm starting out with C# and need to add values to an array, for example:  int[] terms;  for(int runs = 0; runs &lt; 400; runs++) {     terms[] = runs; }   For those who have used PHP, here's what I'm trying to do in C#:  $arr = array(); for ($i = 0; $i &lt; 10; $i++) {     $arr[] = $i; } Elementary central binomial coefficient estimates How to prove that $\quad\displaystyle\frac{4^{n}}{\sqrt{4n}}&lt;\binom{2n}{n}&lt;\frac{4^{n}}{\sqrt{3n+1}}\quad$ for all $n$ &gt; 1 ?     Does anyone know any better elementary estimates?   Attempt.  We have $$\frac1{2^n}\binom{2n}{n}=\prod_{k=0}^{n-1}\frac{2n-k}{2(n-k)}=\prod_{k=0}^{n-1}\left(1+\frac{k}{2(n-k)}\right).$$ Then we have $$\left(1+\frac{k}{2(n-k)}\right)&gt;\sqrt{1+\frac{k}{n-k}}=\frac{\sqrt{n}}{\sqrt{n-k}}.$$ So maybe, for the lower bound, we have $$\frac{n^{\frac{n}{2}}}{\sqrt{n!}}=\prod_{k=0}^{n-1}\frac{\sqrt{n}}{\sqrt{n-k}}&gt;\frac{2^n}{\sqrt{4n}}.$$ By Stirling, $n!\approx \sqrt{2\pi n}\left(\frac{n}{e}\right)^n$, so the lhs becomes $$\frac{e^{\frac{n}{2}}}{(2\pi n)^{\frac14}},$$ but this isn't $&gt;\frac{2^n}{\sqrt{4n}}$. The axiom of extensionality is:  ${\forall}a({\forall}b({\forall}c(((c{\in}a){\iff}(c{\in}b)){\iff}(a=b))))$  The definition of $(P{\iff}Q)$ is:  ${\lnot}((P{\implies}Q){\implies}({\lnot}(Q{\implies}P)))$  or, in other words  $(P{\land}Q){\lor}({\lnot}P{\land}{\lnot}Q)$  In the case of the statement $((c{\in}a){\iff}(c{\in}b))$, this leads us to two options: $((c{\in}a){\land}(c{\in}b))$ and $({\lnot}(c{\in}a){\land}{\lnot}(c{\in}b))$. So far nothing weird. Now, let's see all the possible results of the axiom.  1.$((c{\in}a){\land}(c{\in}b)){\land}(a=b)$ 2.${\lnot}((c{\in}a){\land}(c{\in}b)){\land}{\lnot}(a=b)$ 3.$({\lnot}(c{\in}a){\land}{\lnot}(c{\in}b)){\land}(a=b)$ 4.${\lnot}({\lnot}(c{\in}a){\land}{\lnot}(c{\in}b)){\land}{\lnot}(a=b)$  Coincidentally, they are also all possible statements regarding the statements $((c{\in}a){\land}(c{\in}b))$ and $(a=b)$: both parts are true, the first part is true and the other is false, the second part is true and the first is false and neither is true. The axiom seems not to state anything new, because rephrased it's just produces a list of all possible options regarding the two parts of the statement. Worse, it doesn't seem to say anything about equality, since it allows for $a=b$ with both $(c{\in}a){\land}(c{\in}b)$ and ${\lnot}((c{\in}a){\land}(c{\in}b))$. So, what is the point of this axiom? And in what way does it say anything about equality? What possessive forms are used for mutual 1st person ownership? I want to talk to someone about the house that my wife and I own.  Saying, for example, "My wife's and my house is awesome," sounds a bit funny to me.  What's the best way to express this?  Clarification  I'm asking specifically about the grammar of multiple nouns in possessive form.  I'm particularly curious if it's possible to do this with a first-person pronoun (me).  I am capable of rephrasing this in other ways - my question is not how to express the idea, but about this particular grammatical construction, if it is even legal. Can multiple render systems be used? I was watching a tutorial how to design an island in Blender, which worked really great, but i didn't want to use the .png Trees the guy used there. So i watched another tutorial and created another kind of tree - without knowing that the object isn't just modeled in Cycles Render, it is also rendered in there.  My problem is either the (lets say "simple" textured) island (rendered in Blender render) or the tree is shown. Is there any way i can "convert" that cycles object (with its shaders) to Blender Render or the other way around? Or just render with two renders in one project? I haven't found something about that til now. If there is no universal solution for that, i could also put a link to my project in here. C++ guarantees that variables in a compilation unit (.cpp file) are initialised in order of declaration. For number of compilation units this rule works for each one separately (I mean static variables outside of classes).  But, the order of initialization of variables, is undefined across different compilation units.  Where can I see some explanations about this order for gcc and MSVC (I know that relying on that is a very bad idea - it is just to understand the problems that we may have with legacy code when moving to new GCC major and different OS)?