I just installed Metasploitable 2 from  on VMware Workstation Pro. After logging in, I tried sudo apt-get install whois and I got this error: Reading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed:   whois 0 upgraded, 1 newly installed, 0 to remove and 139 not upgraded. Need to get 31.9kB of archives. After this operation, 279kB of additional disk space will be used. WARNING: The following packages could not be authenticated:   whois Install these packages without verification [y/N]? y Err http://us.archive.ubuntu.com hardy/main whois 4.7.24   404 Not Found [IP: 91.189.91.38 80] Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/w/whois/whois_4.7.24_i386.deb 404 Not Found [IP: 91.189.91.38 80] E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?  This happens with anything, not just whois. I tried sudo apt-get update (with and without -fix--missing), and it ends up with a lot of &quot;Failed to fetch&quot; and ends with an error (&quot;Some index files failed to download...&quot;). If I try sudo apt-get upgrade, I get the same result as installing. I also tried -o Acquire::Check-Valid-Until=false. The date command returned the time in EDT, 7 hours behind my clock, which is correct. I am also connected to the internet since I am able to ping 8.8.8.8. Please can you help me fix it?
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
Should a toggle button show its current state or the state to which it will change? I have a quick question about buttons that toggle between two states. (Think Play/Pause, or Shuffle/Regular Play.) As the title says, should the toggle show it's current state or the state to which it will transition?  I think people are used to the Play/Pause convention. But the Shuffle/Regular play might be more confusing if you show the transition state instead of current. For example, the built-in music player on the Xbox 360 does it this way: when it's in shuffle mode, it shows the icon for direct play and vice versa and it always confuses me (am I in shuffle mode or straight play).  I see it this way: Play/Pause is more like action as in begin playing or pause playing. Yes behind the scenes it is a state transition but to the user, there is an action. Whereas Shuffle/Straight Play is an option and it's best to show the current state (and possibly have only one icon and change button to show that the option is enabled/disabled). Thoughts? Conditional Expectaction 3 variables Suppose $X,Y$ and $Z$ are multivariate normal with means and full covariance matrix. The conditional expectation $E(X | Y)$ is well know. What is the conditional expectation of $E(X | Y,Z)$ if $Y$ and $Z$ (and $X$) are correlated? Standard textbooks only seem to cover the case when $Y$ and $Z$ are uncorrelated. Does "+" use in String concatenation affect efficiency? Do internal forces cause change in velocity? Use of 'prototype' vs. 'this' in JavaScript? What's the difference between  var A = function () {     this.x = function () {         //do something     }; };   and  var A = function () { }; A.prototype.x = function () {     //do something }; How to align prices in columns when both 2 digit and 4 digit variations of a price exist? Dragon souls not activating new words So if I understand correctly you can learn new words and the souls will activate these words. I just killed a dragon and when it died it looked like I absorbed the soul but it didn't unlock any of the words I have.   I noticed some dragons actually have a name so do certain dragons unlock certain words? How do I migrate my Keychain's "Local Items" to a new Mac? After preforming a Mavericks-Mavericks migration using Migration Assistant, I have a "Local Items" Keychain on my new machine in which many (perhaps most) items are out of date (using old passwords), and some are missing altogether. While I have access to a copy of the entire contents of the ~/Library/Keychains/ directory from my old machine, which presumably contains all the information I'm missing, I see no way of importing that information into my new machine.  How can I import the "Local Items" from my old Keychain into the Keychain on my new machine? How does Cooper get out of the black hole? In the movie Interstellar,  Cooper (played by ) enters a black hole and sends a message to Murph (his daughter). Later, he is found by rangers, but I don't understand how he gets out of the black hole?  As far as I know, nothing can get out of a black hole, as it has extremely high gravity. Installing opencv I've downloaded opencv but unfortunately I've got no idea how to install it. All the pages I found online were only telling me how to download and install it directly from the console, not what to do when you already have it downloaded. Could anybody tell me what to do? Selectively coloring text in RichTextBox How can I paint in red every time I meet the letter "A" in RichTextBox? How should we handle downvote retaliation? iPhone asks 'Trust This Computer' again (I am on macOS 10.14.6 and iOS 12.4)   I am certain that I have trusted my Mac before. Without the latter trust, I can also access the phone in iTunes.   I have tried reset "Location and Privacy" on my phone. Then   When connecting the iPhone with iTunes running, it asks for the trust and I trust it.  Reboot my Mac and the phone asks for another trust.   Is there some known malware mimics system behavior and steal data from an iPhone?  (I do have installed some pir*ted software recently. That's my fault.) Why is it dangerous to initialize weights with zeros? Is there any simple example that demonstrates it? Topologist's sine curve is not path-connected Can I send in for repair a lens that has a shattered front element?     UPDATE: The front element was not shattered, it was the UV filter. Factory diagnosis: Lens assembly had been impacted; cleaned and checked.  Helpful notes by Crowley, David Richerby (x2), Michael Clark (x2), and   mattdm (on element price vs UV filter).      Canon cleaned and checked my lens back to like new quality for $179 labor, no parts, not including shipping.      Jim Garrison answered my question, but Crazy Dino has the best info all around for a lens element shatter.   Original Question:  I recently opened my camera bag to find a shattered front element on a Canon EF 16-35mm f/2.8 L II USM lens.   There are a lot of micro glass shards on the second element.  Does anyone have experience with this sort of thing?  Some of the following are questions I have:   Can I get it repaired? What will the cost be roughly? Will the lens ever work the same and have a good image quality? Should I ship it as is, or attempt cleaning it with air? Where is the best place to cry a little?   Thanks, any good info on this would be appreciated.  I will never rest a lens on another lens, I nearly lost a 24-70mm L that shattered a UV filter also.   Good reason to have a UV always, never thought it could happen to me.  Update: Looking at it more it looks like maybe just the front ring came undone and the UV filter broke?  I can't remember what it looked like exactly before.  I threw away the glass shards (polished sand) in the Nevada desert.      UPDATE: Primary reason for thinking more than just the UV was broken,   UV filter split into two rings, depositing the locking collar into the   lens barrel. This came up to me while I was reading the question about Magical being using firearms in battle to raise their power (which I think I have a good answer for, but it's too long to fit in this question... and it would also be inappropriate).  Anyways, I was reading it and then the following thought came into my mind: If wizards decided to use guns on their battles (the ones agains Voldemort for instance), that would create that opening for much bigger battles than we see in the books (after all even a muggle can fire a gun, so lots of guns + the Imperio curse, and presto manifesto (is that racist? talking about wizards and all) you have yourself an army). Those kinds of battles, however, would most definitely not go unnoticed by the muggles - even though they wouldn't be able to link it to magic.  Well, that thought brought up my one and final question, which I bring forth to you guys. Is there any mention on how the Wizards and Witches viewed the two world wars (which had taken part by the time Harry got to Hogwarts, and which he had probably heard about in muggle school), and what was the Wizards' part in it? What about the cold war? Did the magical world even recognise the existence of weapons such as nukes, which could render all life on earth extinct?  EDIT  DVK has brought up an  regarding the connections between the Second World War and the wizarding world (more specifically, the wizard Grindelwald). Although it doesn't fully answer my question, it does help by showing that there was indeed some form of connection between the two world at the time. I need to include code in the appendix of my thesis. The code contains comments and the compilation instantly breaks returning:  Unicode char �\lst@FillFixed@ (U+5A8) (inputenc)                not set up for use with LaTeX. l.160       if (lastArg &lt; 0, lastArg = 360°                                               + lastArg);   This is only one of many characters which produce problems. I cannot change my entire code just because this won't compile. Is there any way to include code with arbitrary unicode characters? Thank you.   Edit: complete sample code, as requested.  \RequirePackage[l2tabu,orthodox]{nag}   \documentclass[headsepline,footsepline,footinclude=false,oneside,fontsize=11pt,paper=a4,listof=totoc,bibliography=totoc]{scrbook} % one-sided   \usepackage[toc,page]{appendix} \usepackage{listings} \usepackage[utf8]{inputenc}  \lstset{     inputencoding=utf8,   extendedchars=true,   basicstyle=\footnotesize\ttfamily,   showstringspaces=false,   showspaces=false,   numbers=left,   numberstyle=\footnotesize,   numbersep=9pt,   tabsize=2,   breaklines=true,   showtabs=false,   captionpos=b,     literate={ö}{{\"o}}1 {ä}{{\"a}}1 {ü}{{\"u}}1  }  \begin{document}  \begin{appendices} \lstinputlisting{code/power_series.html} \end{appendices}  \end{document}   Relevant content of power_series.html:  if (lastArg &lt; 0, lastArg = 360° + lastArg);   There really is not much to say about this problem. I only want to be able to use all unicode characters inside a listing. Thank you. Merge array items into string Why does a monopole not radiate energy in electodynamics?