I frequently run into the problem that I don't have enough space on /boot left. When that happens, I use  to free space.  The output of the command shown there gives me not only a bunch of old (and current) images, but also a lot more headers files. It does not list the current kernel.  foo:~/Desktop $ dpkg -l linux-{image,headers}-"[0-9]*" | awk '/^ii/{ print $2}' | grep -v -e `uname -r | cut -f1,2 -d"-"` | grep -e '[0-9]' linux-headers-3.16.0-38 linux-headers-3.16.0-39 linux-headers-3.16.0-39-generic linux-headers-3.19.0-21 linux-headers-3.19.0-21-generic linux-headers-3.19.0-22 linux-headers-3.19.0-22-generic linux-headers-3.19.0-23 linux-headers-3.19.0-23-generic linux-headers-3.19.0-25 linux-headers-3.19.0-25-generic linux-headers-3.19.0-26 linux-headers-3.19.0-26-generic linux-image-3.19.0-23-generic linux-image-3.19.0-25-generic linux-image-3.19.0-26-generic   I usually remove all but the current kernel and the previous one. However, those headers are way older. Some are 3.16 while I am now on 3.19.  Do I need those, or can I get rid of them?  How do I remove them?
Every time I install a new Linux kernel, it gets left in the grub_config, making the boot menu longer each time.    I know I can manually search through the installed packages and remove them.  Does Ubuntu provide any easier way to clean them up or keep them from showing in the boot list?
What, exactly, is transferred along supply lines? How to draw arrows between circled coefficients of polynomials using tikz After reading Gonzalo's answer to , I thought  I would be able to modify it so that I could have the corresponding coefficients circled and an arrow going from one circle to the next. For example, I would like the coefficient of x^2 on the left, a, circled and the coefficient of x^2 on the right, 5 circled, then a curved arrow drawn between the two circles. How might I achieve this? Also, how would I add some text along the path of the arrow? I reproduce his code here.  \documentclass{article} \usepackage{amsmath} \usepackage{tikz} \usetikzlibrary{calc}  \newcommand{\tikzmark}[1]{\tikz[overlay,remember picture] \node (#1) {};}  \begin{document}  \begin{equation}   a\tikzmark{a}x^2 + bx + c = 5\tikzmark{b}x^2 + bx + c.   \begin{tikzpicture}[overlay,remember picture,out=315,in=225,distance=0.4cm]     \draw[-&gt;,red,shorten &gt;=3pt,shorten &lt;=3pt] (a.center) to (b.center);   \end{tikzpicture} \end{equation}  \end{document} How to use "tens of" and "hundreds of"? If I'm not mistaken, tens of means 10 to 99 and hundreds of means 100 to 999. Is this correct? I found in some dictionaries that tens of is actually not correct.  I also found that hundreds of could also mean any arbitrary large number. So how would people usually interpret hundreds of? Based on context?  In my case, I want to describe numbers of some items that are usually 50-90 but sometimes could be around 100-200, but definitely not as many as 300 or so. I want to really emphasize that there are a lot of these items. In this case, can I say "... have tens or even hundreds of ..."? Would people misinterpret what I actually want to say? Let $\sim$ be the equivalence relation on $S_1 \times I$ given by $(x,t)\sim(y,s)$ if and only if $xt=ys$ where $I=[0,1]$  How do I prove that $(S_1 \times I)/\sim$ is homeomorphic to the unit disk $D^2$ with the induced topology? When searching on a site with  enabled (), I saw some  rendering issues: (and currently it's also in the )        Even though the LaTeX rendering is fine when opening the :        The LaTeX code is:  $f(n) = \begin{cases} 0,  &amp; \text{$ \omega&lt;0, \omega=1, \omega&gt;3 $} \\[2ex] -\omega + 1,  &amp; \text{$ 0\le\omega&lt;1 $} \\[2ex] \omega^2 - 1,  &amp; \text{$ 1&lt; \omega \le 2 $} \\[2ex] 3 \omega,  &amp; \text{$2 &lt; \omega \le 3 $} \end{cases}$ Stupidly, I had been using a condition like this as part of a script:  if [ $(ls FOO* 2&gt; /dev/null) ] # if files named "FOO*" were downloaded  then     echo "Files found"      # ... process and email results else     echo "Not found"     # ... email warning that no files were found (against expectations) fi   That works for zero and one files named FOO*, but fails if there are more than one. From logs I found several different error messages stemming from this:  [: FOO_20131107_082920: unary operator expected [: FOO_20131108_070203: binary operator expected [: too many arguments   My question is: what is the correct way to check, in a Bash if condition, whether one or more files whose name begins with FOO exist?  GNU bash, version 4.2.25(1)-release (x86_64-pc-linux-gnu) Blurring/Feathering a Procedural Pointiness Mask I'm trying to create a procedural mask to affect the sharp edges of my model using the Pointiness output from the Geometry node, leading to the eventual idea of using it to create customisable weathering effects, such as .  This is the base setup that I've got so far.   How is it possible to blur/feather the black edges of the mask so that they would essentially expand across the object until the whole object is rendered black?   I've had a look at both of the go-to texture blur methods suggested for cycles found  and  however these seem to rely on there being a vector input/output for the texture, which is not the case in my example.  The Procedural Cracks tutorial by CGMasters came closest to what I was trying to achieve with the 'Worn Edges' section of the , but I didn't have any success trying to convert it to my situation.  Any ideas would be massively appreciated! :)  EDIT: Not sure if it was clear enough from the description but I'm trying to steer clear of baking/UV-Unwrapping/the Works on this one... Purely procedural :)  UPDATE: I've made a couple of updates to the shader which has given me slightly better results, although it's still not quite there and the mask blur/expansion issue is still not successful.  This is what it now looks like:   The issue is now coming from the grey values of the mask 'leaking' out across the whole mesh and not stemming from the black values... if that makes sense? :P   In researching weathering effects in blender, I stumbled across , which is exactly what I want to achieve?  UPDATE 2: Still no luck achieving the desired effect in the gif, however I feel I'm slightly closer from adding another colour ramp node after the previous ones.    Does anyone have any more ideas?  UPDATE 3: Found a working solution, added an answer below if people are interested :) Yesterday, I was browsing the mobile Stack Overflow site. I noticed one thing: the textareas where you write your comments/answers are very buggy. I'm using a Samsung Galaxy S2, with the standard Android browser (Android version 4.1.2). There are a number of things that aren't working when typing your comment/answer.   Automatic spacing with Swype is disabled (however this might be because of Swype, not the site). Text navigation buttons (step left, step right, select text, copy text etc.) doesn't work with the on-screen keyboard, and selecting text by holding your finger over text is extremely difficult. When you paste something it always seems to be pasted at the top of your text, no matter where you try to paste it. Replying to another comment ("@Example User") does not show suggested people to reply to, like the full site does.   Is there anything I can do to solve these issues/bugs, or is it in the hands of Stack Overflow itself, and if so, should it be looked into?  Edit: I was using the mobile version of the site when noticing these bugs. Table column not align if give color for Table entries My code follows:  \documentclass{book} \usepackage{color,colortbl} \begin{document}  \begin{tabular}{ll&gt;{\color{red}}p{20pc}} a &amp;1 &amp;Test \end{tabular}  \end{document}   The output was:    Some unnecessary vertical space came before the last column. If I remove the tag \color{red} then everything works fine, how can I fix this?  Above said issue was fixed based on the suggestion given by David Carlisle and CarLaTeX, but the same problem was there if I use the supertabular environment, I used supertabular package for auto breaking table and the code follows:  \documentclass{book} \usepackage{color,colortbl,supertabular} \begin{document}  \begin{supertabular}{ll&gt;{\leavevmode\color{red}}p{4pc}&gt;{\leavevmode\color{black}}l&gt;{\leavevmode\color{black}}l&gt;{\leavevmode\color{red}}p{4pc}} a &amp;1 &amp;Test &amp;a &amp;1 &amp;Test\\ a &amp;1 &amp;Test &amp;a &amp;1 &amp;Test\\ \end{supertabular}  \end{document} I shall assume that the sun is at rest, so before the half mass disappear, the orbit of earth is an ellipse. Pass an extra argument to a callback function Why is it impossible to override a getter-only property and add a setter? Why is the following C# code not allowed:  public abstract class BaseClass {     public abstract int Bar { get;} }  public class ConcreteClass : BaseClass {     public override int Bar     {         get { return 0; }         set {}     } }      CS0546 'ConcreteClass.Bar.set': cannot override because 'BaseClass.Bar' does not have an overridable set accessor Reading through this doc:      We replaced the rich text editor in HTML Area home page components   with a new version that supports more markup but doesn’t allow HTML to   be manually entered.      In Summer ’15 we will start removing unsupported code from HTML Area   home page components. As a result, components that contain JavaScript,   CSS, iframes, or other unsupported markup might stop working properly.   To use JavaScript or other advanced HTML elements in your home page   component, we recommend that you use a Visualforce Area component   instead.   With Visualforce homepage component the best we could do is design fancy home page components, which has not been the big use of sidebar amongst developers. How do we do the fancy hack we do today using html components since visualforce is hosted in a different domain will the sidebar hacks even work after summer 15?     You can include JavaScript in your Visualforce page, but because the   component is rendered in an iframe on the home page layout, the   JavaScript can’t interact with the page that contains the component.   Finally why this move :(? I was wondering if it's possible to run an Ubuntu virtual machine using VirtualBox in background, I mean, without any window open.  The idea is to connect via SSH to the Linux host, that would be running in background.  Has anyone ever done something like this? Is it possible? Let $G$ pe a $p$ group. I have to show that         the number of nonnormal subgroups is divisible by $p$       the number of subgroups differs from the number of normal subgroups by a power of $p$.   Are there any theorem that can help me to prove this ? We have discussed the Sylow theorems but I don't know how to apply them - if those are the theorems I need. (Does this theorem also hold for infinite groups $G$ ?) Rich Wizards, Poor Muggles Why, oh why, don't the Weasleys "conjure" up some diamonds/gold/etc, sell 'em to Muggles, and get rich? They could buy a mansion (like the Malfoys), and live there happily ever after.  I know there's  that prohibits one from conjuring food (which doesn't make much sense to me, either). Even if it applied to gold, what about all the other elements/compounds/materials? Could the law really be 'don't let a wizard conjure something if it'll make them richer'? That's totally nonsensical.  Why does Wizard society still have poor people, especially if they're talented? Access server by host name? I have a mixed network with mostly Windows machines, a Mac, and a few Linux boxes.  There is no DNS or WINS server, and adding one is outside of my control.  If I put a clean install of 10.04 desktop on a computer, then all other machines on the network can get to that machine by hostname just fine.    However, if I put 10.04 server on the same computer, then the other machines can only get to it by IP address.  The hostname does not resolve.  What do I need to do on the server so that all the other machines on the network can get to it? Python BeautifulSoup findAll by "class" attribute Dynamically Adding/Removing CSS in Nested Div I am about to start a web project and have been working almost exclusively with a LAMP stack for the past 5 years.  I would like to build something larger and more scalable and hence have been looking into Java EE.  The division of logic between JSP and EJB seems ideal for what I want to do.  Can anyone recommend resources for getting familiar with Java EE?  And perhaps if anyone knows of technologies that are more scalable than PHP that I should consider as well, I'm all ears.  Thanks a lot!