OS X is my host OS.  I have windows xp and Ubuntu 10.10 on guest OS. They both work great.  When I eject USB flash drive from host OS, it appears in windows guest OS  but it does not appear in Ubuntu Guest OS.   I never run both guest OS at the same time. It's always either or.  I am running, VM VirtualBox 4.1.10 and installed latest guest additions and also installed VM virtualbox extension pack.
I'm using Ubuntu Maverick and Virtual Box 3+. I have Windows 7 Ultimate. The problem is that it doesn't detect USB drives in Windows 7, but USB peripherals (mouse + keybord) are working.  I followed , but I can't find the user group vboxusers. How can I continue? I would also like to upgrade to the latest version without any risk (without losing my virtual hard disk drive).
Let $A ∈ M_{m\times n}(\mathbb{Q})$ and $B ∈ \mathbb{Q}^m$. Suppose that the system of linear equations $AX = B$ has a solution in $\mathbb{R}^n$. Does it necessarily have a solution in $\mathbb{Q}^n$?  Where do I start?    I feel I can use this to :  $$x_i=\frac{1}{a'_{ii}}\left(b'_i - \sum_{j=i+1}^{k} a'_{ij} x_j \right).$$    Here is a thought that just crossed my mind, but I'm not sure if this is legal:  Suppose $Y\in \{\mathbb{R}\setminus \mathbb{Q}\}^n$ and $Y'\in\mathbb{Q}^n$ are solutions to $AX=B$. Then $AY=AY'=B$, or $A(Y-Y')=A(Y+(-Y'))=0$, but  addition between $\{\mathbb{R}\setminus \mathbb{Q}\}^n$ and $\mathbb{Q}^n$ is . . . I remember reading this as a kid and it starts out with:   a boy in his home village where the other kids are mean to him during sports and they heat up their home with floating logs or something.   The kid is being hunted by some reaper character and that reaper finds him at a place called "The Edge" or something similar.   He buys a glove covered in an expensive dust that purifies things and is really rare.  In one book they had to climb down the edge for some reason.  There was another part where people only communicated telepathically and when sneaking into somewhere he only thought of light.  One of the main things is the floating ships and how he is really good at flying them and he assembles a team for a mission or something.  There is like float powder and stuff.  I read this close to 10 years ago. In my test class i have the creation of a dummy custom setting and a dummy lead:  Group g1 = new Group(Name='group name', type='Queue');              insert g1;             QueuesObject q1 = new QueueSObject(QueueID = g1.id, SobjectType = 'Lead');              insert q1;       SetOwner__c mycs = SetOwner__c.getValues('standardset');               if(mycs == null) {                               mycs = new SetOwner__c(Name= 'CustomValues');                  mycs.OwnerId__c ='00520000000z3PrAAI';                  mycs.RecordtypeID__c='012L00000004QsrIAE';                  insert mycs;      Lead lead = createNewLead(u2.id);                           insert lead;   ERROR:  MIXED_DML_OPERATION, DML operation on setup object is not permitted after you have updated a non-setup object (or vice versa): SetOwner__c, original object: QueueSobject: []   I get this error because i am trying to perform DML on setup and non-setup objects in the same transaction.  Any solution for this problem? I want my Java code to be typeset in a monospaced font, so I am using the verbatim environment. LaTeX commands are highlighted in Eclipse, but as soon as I use the verbatim environment everything inside and the color of the environment itself becomes gray.  \begin{verbatim}   public class main {  public static void main (string[] args){      for(int i = 0; i &lt; arg.length; i ++){          System.out.println(args[i]);      }    }  };  \end{verbatim}   I'm using the verbatim and alltt packages.  Update 1.  MWE.  \documentclass[xcolor=dvipsnames]{beamer}  \mode&lt;presentation&gt; { \usetheme{CambridgeUS} \setbeamercovered{transparent} }  % Поддержка русского языка \RequirePackage[utf8]{inputenc} \RequirePackage[T2A]{fontenc} \RequirePackage[russian]{babel}  \RequirePackage{amsfonts}  \usepackage{algorithmic} \usepackage{mathptmx} \usepackage[scaled=.90]{helvet} \usepackage{courier} \usepackage{pst-node} \usepackage{pst-tree} \usepackage{auto-pst-pdf} \usepackage{color} \usepackage{colortbl} \usepackage{pstricks} \usepackage{verbatim} \usepackage{alltt} \usepackage{listings} \usepackage{animate} \usepackage{multimedia}  \title{Title}  \author{Name}  \institute{}  \date{\today}  \begin{document}  \begin{frame} \titlepage \end{frame}  \begin{frame} \frametitle{Outline} \tableofcontents \end{frame}  \section{Introduction}  \begin{frame}{Классификация по поколениям}  \begin{itemize}  \item Третьего поколения (высокоуровневые языки) - последовательность высокоуровневых конструкций (циклы, условные выражения, классы, интерфейсы, методы, процедуры, \ldots) \pause  \begin{exampleblock}{Пример}  \begin{centering}  Fortran, C, C++, C\#, Java, Lisp.  \begin{verbatim}  public class main { public statiс void main (string[] args){ for(int i = 0; i &lt; arg.length; i ++){ System.out.println(args[i]); } } };  \end{verbatim}  \end{centering}  \end{exampleblock}\pause  \item Четвертого поколения (для конкретного применения) - последовательность инструкций конкретной предметной области \pause  \begin{exampleblock}{Пример} SQL, Postscript, XML, Mathlab. \end{exampleblock} \pause  \end{itemize}  \end{frame}  \end{document} This is a comic book I read no later than 1993 (so is pre-1993).  And probably after 1988 though I can't be certain.  The protagonist is a huge barbarian with an axe, who seems like an old man, who is defending a series of gigantic walls against an invading army, apparently single-handedly. They keep having to fall back to inner walls. He has to get a massage at one point (not that kind of comic btw).  It's not a super-hero or funny comic, it's more of a serious graphic novel.  That's about it, sorry it's so vague. Unable to lock the administration directory (/var/lib/dpkg/) is another process using it? I get this error when trying to use apt-get:  E: Could not get lock /var/lib/dpkg/lock - open (11 Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/) is another process using it?     How can I fix this? On the bash command-line, ↑ gives me the previous command. On the command-lines in ipython or matlab, when I type a few characters, ↑ gives me the previously entered command starting with those characters. How can I enable exactly this behaviour in bash? I am aware of more advanced ways of searching through the command-line history, but sometimes a simple way is more convenient. Show that $2730\mid n^{13}-n,\;\;\forall n\in\mathbb{N}$   I tried, $2730=13\cdot5\cdot7\cdot3\cdot2$  We have $13\mid n^{13}-n$, by Fermat's Little Theorem.  We have $2\mid n^{13}-n$, by if $n$ even then $n^{13}-n$ too is even; if $n$ is odd $n^{13}-n$ is odd.  And the numbers $5$ and $7$, how to proceed? How to factor numbers that are the product of two primes "Protect Questions" privilege page has confusing wording The wording on the  privilege page is confusing and would benefit from being clarified. See these questions on  and . Suggested wording from  is to replace this:  Which questions can be protected? Any question, even a deleted question, can be protected and unprotected, subject to the following restrictions:  The question must be at least a day old A user can unprotect any protected question   with the following:  Which questions can be protected? Any question at least a day old, even a deleted question, can be protected and unprotected. A user with the privilege can unprotect any protected question. Should VMware Tools always be installed in headless Linux guests? We have a deployment with what I would call an Enterprise Cloud Provider. It's VMWare Infrastructure 3.5.x and includes VMotion / VMWare HA instances, etc.  At Provider 1 VMWare Tools was installed:   vmware-guestd is running and; at least two kernel modules are loaded, vmmemctl &amp; vmhgfs   Provider 1 does nightly VM Snapshots.  We are beginning a new deployment at Provider 2 (also an Enterprise Cloud Provider). They did not install VMWare Tools. Provider 2 does not do nightly VM Snapshots but rather file-system backups (using an agent).  From my reading it seems like at the very least VMWare Tools should be installed for the Memory Balloon Driver (vmmemctl) and from reading sources like  it suggests that certain VirtualCenter management operations also depend upon VMWare Tools being installed in the Linux guest.  Note that all of our instances are headless (default runlevel is 3) and RHEL.  It is hard to find authoritative information on this question and the aforementioned source is somewhat dated.  Can someone shed some light on this? What are the factors/criteria that would lead to an answer in the affirmative or negative?  TIA  Cheers Proof that $\suṃ̣_{k=1}^{n}k {n \choose k}$ for $n \in \mathbb N$ is equal to $n2^{n-1}$.  As a hint I got that $k {n \choose k} = n {n-1\choose k-1} $.  I tried solving this by induction but, in the inductive step I'm not arriving to the correct result. Execute function when post is published I try to use this function i have created when a post is published for the first time.  function a_new_post($post){   $post_id = $post-&gt;ID;    if ( !get_post_meta( $post_id, 'firstpublish', $single = true ) ) {       // ...run code once       update_post_meta( $post_id, 'firstpublish', true );   } } add_action( 'draft_to_published', 'a_new_post' );   I can't see anything wrong with it, but when i try to create some sample posts i check the database and the field "firstpublished" has not been created.  Does anyone see anything wrong? Let's say we are talking about the indigenous pukapuka who live in Pluto.  What is correct: "the pukapuka people" or "the pukapuka peoples"?  I've read somewhere the usage of "peoples" in this context, and it has surprised me. How do I perform an IF...THEN in an SQL SELECT statement?  For example:  SELECT IF(Obsolete = 'N' OR InStock = 'Y' ? 1 : 0) AS Saleable, * FROM Product The spell Armor of Agathys states:      You gain 5 temporary hit points for the duration. If a creature hits you with a melee attack while you have these hit points, the creature takes 5 cold damage.   Now, assume my buddy uses Inspiring Leader to give me 10 temporary hit points — does the effect end? I have a MacBook Pro 2009 running MacOS El Capitan. Recently the Wi-Fi has stopped working.   When I click on the Wi-Fi icon it displays the message "No hardware installed", but Ethernet still works.   Is there any way of fixing this by using a Wi-Fi dongle or something of the sort, if so do I need a specific dongle and how do I install it? What happens if I activate a product key on Steam for a game I already own? I have a Steam product key for Just Cause 2 I got for free with the purchase of my video card. However, I already have a copy of this game attached to my Steam account. What will happen if I try to activate this other key on my account? Will Steam give me a copy of Just Cause 2 to gift to somebody else? Will it simply refuse to add it? Or will it eat the key rendering it worthless?  I don't want to try this only to have the latter happen, but it would be useful to be able to add it and gift it to somebody else. Proving any number of the form $2^n$ can't be written as the sum of k consecutive numbers. .fbx export why there are no materials or textures? I used node textures in a mesh I exported to .FBX.  I then imported it into Unreal Engine 4 and it didn't import any textures; I clicked the Upload Textures option in Unreal Engine.  Is there something I'm doing wrong or is it Blender?