How to set default kernel in GRUB without Grub Customizer? After the recent update I wasn't able to start my system (black screen). So I powered off the PC and turned it on again.  Saw the following grub menu:  Ubuntu Advanced options for Ubuntu System setup   I selected "Advanced options for Ubuntu" and saw:  Ubuntu, with Linux 4.2.0-42-generic Ubuntu, with Linux 4.2.0-42 ... (recovery mode) ... Ubuntu, with Linux 4.2.0-41-generic Ubuntu, with Linux 4.2.0-41 ... (recovery mode) ... ...   I selected Ubuntu, with Linux 4.2.0-41-generic and the system started (previously with Ubuntu, with Linux 4.2.0-42-generic selected it didn't)  As I didn't always want to select it manually I tried to set it as the default kernel in grub: So I opened '/etc/default/grub' and changed:  GRUB_DEFAULT=2   Then executed $sudo update-grub and restarted the system. But it still wanted to load the latest kernel.  I also tried it with GRUB_DEFAULT=3 but the result was the same.  My grub is:  #grub-install --version grub-install (GRUB) 2.02~beta2-9ubuntu1.11   I also got some errors while installing grub customizer:  ... dpkg: dependency problems prevent configuration of linux-signed-generic-lts-wily:  linux-signed-generic-lts-wily depends on linux-signed-image-generic-lts-wily (= 4.2.0.42.34); however:   Package linux-signed-image-generic-lts-wily is not configured yet.  dpkg: error processing package linux-signed-generic-lts-wily (--configure):  dependency problems - leaving unconfigured Setting up grub-customizer (5.0.6-0ubuntu1~ppa1t) ... Errors were encountered while processing:  linux-image-4.2.0-42-generic  linux-image-extra-4.2.0-42-generic  linux-image-generic-lts-wily  linux-generic-lts-wily  linux-signed-image-4.2.0-42-generic  linux-signed-image-generic-lts-wily  linux-signed-generic-lts-wily E: Sub-process /usr/bin/dpkg returned an error code (1)   So I'm not sure whether I should reboot or uninstall it...
Set "older" kernel as default grub entry I installed a mainline kernel for testing purposes. I would like to set grub to boot from the older kernel by default.  I know I can set the GRUB_DEFAULT=0 setting for the first page of grub but how do I set it to boot by default from one kernel in the second page (Advanced page)?  I would prefer doing this without installing other software (ex. grub-customizer).     Related Questions:
"There is no point in" or "There is not a point in" I was thinking about these negations. Do these mean the same thing?     There is no point in ...   There is not a point in ...   or:     I have no clue   I do not have any clue     etc. Are there any tools for Windows 7 that will allow me to enable/disable monitors from the command-line?  For example, my GTX 480 has three outputs (2x DVI and 1x HDMI) but only two displays can be active at any given time.  I'd like for a command-line to allow me to disable one of the DVI monitors and enable the HDMI monitor, etc.  (I've found NirCmd which is an amazing utility but it doesn't seem to support this...)  EDIT: UltraMon seems capable of doing this but I really hoping for a more light-weight command-line solution... Constructing the reciprocal of a segment How can one construct the reciprocal length of a line segment? For example, given any line segment a, how can $\frac{1}{a}$ be constructed?  I was told that it can be solved by creating similar triangles, but I do not get it. Direct way leads to nowhere.  $$\lim_{n\rightarrow \infty} \sum^{n}_{i=1} \frac{1}{\sqrt {n^2 +i} } = \lim_{n\rightarrow \infty} \sum^{n}_{i=1} \frac{1}{n \sqrt {1 +\frac{i}{n^2}} } = $$  $$ = \lim_{n\rightarrow \infty} \frac{1}{n} \cdot \lim_{n\rightarrow \infty} \sum^{n}_{i=1} \frac{1}{\sqrt {1 +\frac{i}{n^2}} } = 0 \cdot \sum^{n}_{i=1} 1 = 0 \cdot n $$  So, I tried to apply squeeze theorem:  $$\lim_{n\rightarrow \infty} \sum^{n}_{i=1} \frac{1}{\sqrt {n^2 +i} } \leq \lim_{n\rightarrow \infty} \sum^{n}_{i=1} \frac{1}{n}  = 1$$  Could you help me to figure out the lower bound? The message that appears in the reputation tab of a user's profile when they gain or lose reputation due votes disappearing when another user is deleted is simply:     user was removed   This message is confusing and unhelpful. Below are comments that demonstrate this confusion, . I don't have any quotes from the users who could not find it and remained confused.  There is , and . However, the message has not been changed.  I know that in the past the developers have been reluctant to direct users to meta in some situations, such as question bans, because it may cause users to post here appropriately. That does not seem to apply to this case. This is not typically a case of ""; most of us have probably seen the message at some point.  Why is this message vague and unlinked? What negative behaviour does this confusion mitigate?       My first interpretation was that I was the user who was removed!        I just simply wished the explanation on the reputation page was better. Seems like I shouldn't have had to come to the meta section to figure this out.        It must be better to show "User  was removed". For a moment I just thought that I was removed :-(        the information should be better. I lost 10 points yesterday by "user removed" and assumed that I was the one being removed, leaving me wondering why and feeling somewhat embarrassed.         The recalc policy is fine. But the red mark and "user was removed" looks cryptic and unnecessarily negative--especially since the only user name mentioned on a profile is one's own. So the natural impulse is to bind "user" to the account you're looking at. (It was jarring to me and I could tell what it meant, but still this could be clearer.) I agree that orange is better than red and ideally all of these things would have hyperlinks to a help page (or at least a meta post) explaining what the deal is.        +1 (to HostileFork) for the idea of linking to an explanation of 'User was removed'. It just took me 10+ minutes to find this particular thread and read through, when I could have simply clicked through! I would also like a little more info on why user was removed (abuse, friend upvotes, rules, etc) , as that could help educate the community as a whole on what behaviors to report.        I could care less about the rep gain or loss, but when you have a loss it is a scary message without context. I honestly thought for a moment that my account had been inhibited in some way. No, it didn't say "Your account was removed." Still, there is that moment of "what did I do wrong?" which seems silly to cause simply by not posting a few extra words. A clearer "A user who voted on your posts was removed along with reputation changes they caused" would have gone a long way to not cause me to question my participation in the review queues as of late.         My problem is that the message "user has been removed" is not a clickable link like the other messages - so I had to search meta to discover this question to find out what it meant. How can I fix apt error "W: Target Packages ... is configured multiple times"? How to suppress scientific notation when printing float values? Here's my code:  x = 1.0 y = 100000.0     print x/y   My quotient displays as 1.00000e-05.  Is there any way to suppress scientific notation and make it display as 0.00001? I'm going to use the result as a string. I want to create a math problem-solution sheet. The coefficients a, b, c must be assigned on the fly at random so the generated pdf will show a numeric quadratic equation rather than a symbolic quadratic equation. Note a must not be zero.  \documentclass{article} \begin{document} \section{Problem} Let \(x_1\) and \(x_2\) be the roots of \(a x^2 +bx +c=0\). Find  \(x_1x_2\).  \section{Solution} \[ x_1x_2=\frac{c}{a} \] \end{document}   Please kindly make the solution get automatically simplified. For example: \frac{c}{a}=3 when a=2 and c=6.    Actually the real case is more complex than this one. Not only the equations must be generated at random, but also the associated graphic plots that I write in PSTricks.     I chose Paulo's answer because using Maxima as the computation engine is very very great idea. Other answers are also good and creative, especially Altermundus'. Why aren't we sterilizing N95 masks? How do I address unchecked cast warnings? Eclipse is giving me a warning of the following form:     Type safety: Unchecked cast from Object to HashMap   This is from a call to an API that I have no control over which returns Object:  HashMap&lt;String, String&gt; getItems(javax.servlet.http.HttpSession session) {   HashMap&lt;String, String&gt; theHash = (HashMap&lt;String, String&gt;)session.getAttribute("attributeKey");   return theHash; }   I'd like to avoid Eclipse warnings, if possible, since theoretically they indicate at least a potential code problem.  I haven't found a good way to eliminate this one yet, though.  I can extract the single line involved out to a method by itself and add @SuppressWarnings("unchecked") to that method, thus limiting the impact of having a block of code where I ignore warnings.  Any better options?  I don't want to turn these warnings off in Eclipse.  Before I came to the code, it was simpler, but still provoked warnings:  HashMap getItems(javax.servlet.http.HttpSession session) {   HashMap theHash = (HashMap)session.getAttribute("attributeKey");   return theHash; }   Problem was elsewhere when you tried to use the hash you'd get warnings:  HashMap items = getItems(session); items.put("this", "that");  Type safety: The method put(Object, Object) belongs to the raw type HashMap.  References to generic type HashMap&lt;K,V&gt; should be parameterized. Using local OpenStreetMap (*.OSM) map with Openlayers 3? What do I need to load a .OSM map in a client side javascript app? (Imagine an offline webapp). Correlations between continuous and categorical (nominal) variables I would like to find the correlation between a continuous (dependent variable) and a categorical (nominal: gender, independent variable) variable. Continuous data is not normally distributed. Before, I had computed it using the Spearman's $\rho$. However, I have been told that it is not right.  While searching on the internet, I found that the boxplot can provide an idea about how much they are associated; however, I was looking for a quantified value such as Pearson's product moment coefficient or Spearman's $\rho$. Can you please help me on how to do this? Or, inform on which method would be appropriate?  Would Point Biserial Coefficient be the right option? Is Duck/Duct tape safe to use to insulate mains wires? Question says it all really. Based in the UK so mains is 240v and 20 amps. It's a lighting circuit. Laptop Overheating. Is there a way to cool it? I have a laptop that's running on the following:   MSI MS-1634X motherboard AMD Turion X2 TL-66 CPU ATI Mobility Radeon HD2600   It keeps overheating, especially when I do something more CPU and GPU-intensive such as games. I've tried SpeedFan and Notebook Hardware Control and neither are able to help control my fans. I also have a Targus Chillmat for my laptop which helps cool down my laptop, but it still overheats. Are there any fan controlling programs that I could use to maybe turn up the RPMs on my fans or any other ways to cool down my laptop? My laptop runs pretty hot, maybe 80c core when being used, not even intensively. The Hard drive stays cool though, close to 35c.  Any help is appreciated. Thanks! I wanted to add classpath to my JDK. While searching a way to do it I noticed everyone open .profile file using terminal. But when I want to open and edit it with a text editor I couldn't see that file in Home folder.  Can someone tell me why is this. And also if possible how can I access .profile in home folder the GUI way. Nesting quotes in JavaScript/HTML How do I get a really wide tilde?  I need to cover at least  abcdefghijklmnopqrstuvwxyz  The \widetilde command does not work. Nor using \stackrel with \sim. Inclusion of Fields whose order is a prime power Blue was correct, I need to fix my understanding of this:     Finite fields have cardinality of a prime order because they have a prime subfield that has finite characteristic.    I do not completely understand why finite field of each characteristic is unique. Perhaps we look at a polynomial and express the finite field as a splitting field? And we use uniqueness of splitting fields?  Then, why is it that  $\mathbb F_{p^m} \subseteq \mathbb F_{p^n}$ if and only if $m$ divides $n$? With ksh I'm using read as a convenient way to separate values: $ echo 1 2 3 4 5 | read a b dump $ echo $b $a  2 1 $  But it fails in Bash: $ echo 1 2 3 4 5 | read a b dump $ echo $b $a     $  I didn't find a reason in the man page why it fails, any idea? Drawing a constant randomly distorted circle I am trying to draw a special and contradictive plot : A circle with random distortions which have to remain constant regardless of how many times I build the document.  An example of what I am trying to achieve can be seen below    This figure was produced with the following code  \documentclass{standalone} \usepackage{tikz}    \usetikzlibrary{decorations.pathmorphing}   \begin{document}     \begin{tikzpicture}         % axes         \draw[ultra thin] (-2.5, 0) -- (2.5, 0);         \draw[ultra thin] (0, -2.5) -- (0, 2.5);         % undistorted sphere         \draw[ultra thin, dashed] (0, 0) circle (2.25cm);         \draw[ultra thin, dashed, -&gt;] (0:0) -- (125:2.25);         \node at (-1, 1) {$R$};         % distrorted sphere         \draw[very thick] plot[domain=0:350,smooth cycle ] (\x:2+rnd*0.5);         \draw[very thick, -&gt;] (0:0) -- (45:2.1);         \draw[ultra thin, -&gt;] (1, 0) arc (0:45:1);         \node at (1.2, 0.4) {$\theta$};         \node at (0.7, 1.25) {$R(\theta)$};     \end{tikzpicture} \end{document}   The problem with the code is that whenever I make a change to it and rebuild the document, the "distorted" circle will have a different shape, since I am using the rnd function. The reason I would like to have a constant-random shape is because I would like to denote its radius at an angle θ, therefore it has to touch the outline of the circle.  Any idea on how to achieve such a thing?