What does the 'd' mean in ls -al results and what is that slot called?
Understanding UNIX permissions and file types
Converting numpy dtypes to native python types Correct ssh config file settings to tunnel to a 3rd machine I'm trying to tunnel to a server via a bridge server. So far, I've been able to get it working from the command shell properly using the following command:  ssh -A -t bridge_userid@bridgemachine.com ssh -A remote_userid@remoteserver.com   But I've been trying to wrap this into my ~/.ssh/config file and I have troubles. I've tried:  Host axp   User          remote_userid   HostName      remoteserver.com   IdentityFile  ~/.ssh/id_rsa.eric   ProxyCommand ssh -A -t bridge_userid@bridge_userid.com ssh -A remote_userid@%h   But when I do, I get the following error message from remoteserver.com and I'm not sure what is causing it:     ksh: SSH-2.0-OpenSSH_6.8^M:  not found   I know that when I log into remoteserver.com , my shell is /usr/bin/ksh.  I've tried to add path arguments to the ssh commands in the config file, but it made no difference.  Any ideas what it can be? What is with words that have forms that end both in -zation and -sation, such as localization and localisation?  Many spell checkers recommend -zation. How do I get permissions to edit system configuration files? Is there a way to resolve probability of an event, given another event that never happens? Mathematically speaking the problem is:  Given that $P(B) = 0$,  $$P(A|B)=\frac{P(A \cap B)}{P(B)} = \frac{0}{0}$$  Is this probability vacuously $0$ of $1$? Can we show that it's one or the other? Removing OS from Dual Boot computer, and recovering HD space. I have a computer that dual boots Linux Mint, and Ubuntu, I am wondering what the best way would be to remove Linux Mint, then recovering the hard drive space that is resides in so that Ubuntu will be able to access it. using a:hover to change the color of an image Where does TREE(n) sit on the Fast Growing Hierarchy? How would you implement an LRU cache in Java? Please don't say EHCache or OSCache, etc. Assume for purposes of this question that I want to implement my own using just the SDK (learning by doing). Given that the cache will be used in a multithreaded environment, which datastructures would you use? I've already implemented one using  and , but I'm curious if any of the new concurrent collections would be better candidates.  UPDATE: I was just reading through  when I found this nugget:     If you need constant-time access and want to maintain the insertion order, you can't do better than a LinkedHashMap, a truly wonderful data structure. The only way it could possibly be more wonderful is if there were a concurrent version. But alas.   I was thinking almost exactly the same thing before I went with the LinkedHashMap + Collections#synchronizedMap implementation I mentioned above. Nice to know I hadn't just overlooked something.  Based on the answers so far, it sounds like my best bet for a highly concurrent LRU would be to extend  using some of the same logic that LinkedHashMap uses. I am trying the fallowing exercise : Solve $P(X^2 -2)=P(X)^2 -2$ with P a monic polynomial (non-constant)  My attempt :  Let P satisfying $P(X^2-2) = (P(X))^2-2$  Then $Q(X)=P(X^2-2) = (P(X))^2-2$   Therefore,  $$Q(X^2-2) = (P(X^2-2))^2-2 = (P(X)^2-2)^2-2 = Q^2-2$$  As X is a solution, by defining the sequence:  $(P_n)_{n \geq 1}$ with $P_1 = X$ and for all $n \geq 1, P_{n+1} = P_n^2-2$  We obtain a sequence of polynomials which are solutions.   But I don't know how to prove it's the only one. If someone have an idea to prove it or an another method to solve the problem ?   Thank you in advance for your time. I have a netbook with an AZERTY layout. I've changed it to "bépo" to try it, but now I've reset it to a french layout.  While all the apps have taken the change into account, Ubuntu's login manager still uses bépo, making entering passwords a challenge. I've enabled the virtual keyboard for the time being so that I could login again.  I don't remember what I had done in the first place to switch the login screen to bépo, but now I can't switch it back.    EDIT : In the keyboard settings page, if I click "use system defaults", then everything is in bépo ! Where is this different keyboard layout set ?  ANOTHER EDIT : Here's what did not work :   Changing the layout in settings using the "use system defaults" checkbox in settings sudo dpkg-reconfigure keyboard-configuration changing it in Xconf adding a line in /etc/lightdm/lightdm.conf  sudo dpkg-reconfigure locales slaming head against desk dpkg-reconfigure lightdm sudo gsettings set org.gnome.libgnomekbd.keyboard layouts "['fr']" combinations of the above     Is it possible to relaunch the keyboard configuration tool that's in ubuntu's setup ? The thing has automatic layout detection and it changes the setting everywhere. Selecting text in profile activity comments causes unexpected clipping This is a very minor bug I know, but in anyone's profile page, on the Activity or Responses tab, text highlighting is messed up for the Comment and All subcategories. This only seems to happen only in Chrome. I am on Version 31.0.1650.63 (Win 7). It is visibly worse on multiple lines of text.     Steps to repro:   Go to any profile on any Stack Exchange site, and click on Activity tab. Go to All or Comment subcategories. Highlight text.   As a side effect, you can even temporarily dismember the head of all those poor characters. To do this, start from any line, drag mouse left or right, drag up and then back down.    I've bumped into bugs before that turned out to be Chrome problems, so maybe this is just Chrome doing its magic. Find path of standard executable for a given file type in Windows Suppose I am running cmd and I open an application by typing for example start document.pdf  I want to get the exact path of the executable that opens .pdf files  Of course I could search the entire system for the executable but I suppose it would be faster this way because the path is already stored somewhere  I don't know if it makes a difference but I am using Windows 7 Is SSIS subject to the maximum memory limitations for SQL Server 2012 Standard edition?  If I have a server with 128GB RAM and I allocate 64GB of RAM to SQL Server does SSIS utilise this memory or does it utilise the memory that is available to the OS?  I am assuming it utilises the remaining memory left to the OS since there is no settings for memory consumption and it runs as a separate service.  If anyone has any information on the available memory that should be left for SSIS to consume I would appreciate the help. Can $\sqrt{n} + \sqrt{m}$ be rational if neither $n,m$ are perfect squares? How can I install a package without root access? Why didn't the Order of the Phoenix assist with the trio (i.e.  Harry Potter, Ron Weasley and Hermione Granger) in the Horcrux hunt? In a tennis tournement of 128 players, elimination system, what is the probability that two twins will meet at some point? Tikz, Tree without overlaps I'm trying to get a nice tree without the overlaps, can anyone help me to improve my code?  \documentclass{standalone} \usepackage{amssymb} \usepackage{amsmath} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage{dsfont} \usepackage{tikz} \usetikzlibrary{shapes} \usetikzlibrary{graphs}  \begin{document}       \begin{tikzpicture}[baseline,level/.style={level distance=20mm, sibling distance =35mm/#1},scale=1]         \node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}             child{ node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}                 child{ node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}                     child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                     child{ node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}                         child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                         child{ node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}                             child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                             child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                         }                     }                 }                    child{ node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}                     child{ node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}                         child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                         child{ node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}                             child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                             child{ node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}                                 child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                                 child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                             }                         }                     }                     child{ node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}                         child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                         child{ node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}                             child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                             child{ node [ellipse split, draw] {$s_1&lt;s_2$\nodepart{lower}\tiny $(s_1,s_2,s_3,s_4)$}                                 child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                                 child{ node [rectangle, draw] {$(s_1,s_2,s_3,s_4)$}}                             }                         }                     }                 }             };     \end{tikzpicture} \end{document} Let $F$ be a field and $F^\times$ be its group of units. If $F^\times$ is cyclic, then show that $F$ is finite.  I'm a bit stuck. I know that I can represent $F^\times = \langle u \rangle$ for some $u \in F^\times$ and that we must have that $|F^\times| = o(u)$, where $o(u)$ denotes the order of $u$ in $F^\times$.  I tried assuming $o(u) = \infty$, but I'm not sure exactly where to go from there. I was wondering if I could get a hint.