Here's what I keep getting when I sudo apt update  Hit:1 http://archive.canonical.com/ubuntu xenial InRelease Ign:2 http://dl.google.com/linux/chrome/deb stable InRelease                    Get:3 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]      Hit:4 http://dl.google.com/linux/chrome/deb stable Release                      Hit:5 http://ppa.launchpad.net/gnome3-team/gnome3-staging/ubuntu xenial InRelease Hit:6 http://ppa.launchpad.net/gnome3-team/gnome3/ubuntu xenial InRelease       Hit:7 http://eg.archive.ubuntu.com/ubuntu xenial InRelease                      Hit:8 http://ppa.launchpad.net/linrunner/tlp/ubuntu xenial InRelease      Get:9 http://eg.archive.ubuntu.com/ubuntu xenial-updates InRelease [102 kB] Hit:10 http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu xenial InRelease    Hit:12 http://ppa.launchpad.net/openjdk-r/ppa/ubuntu xenial InRelease           Hit:13 http://ppa.launchpad.net/plushuang-tw/uget-stable/ubuntu xenial InRelease Hit:14 http://ppa.launchpad.net/ubuntu-desktop/gnome-software/ubuntu xenial InRelease Get:15 http://eg.archive.ubuntu.com/ubuntu xenial-backports InRelease [102 kB] Hit:16 http://ppa.launchpad.net/ubuntu-desktop/ubuntu-make/ubuntu xenial InRelease Hit:17 http://ppa.launchpad.net/webupd8team/y-ppa-manager/ubuntu xenial InRelease Hit:18 https://packages.microsoft.com/ubuntu/16.04/mssql-server xenial InRelease Get:19 http://eg.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages [540 kB] Err:19 http://eg.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages   Hash Sum mismatch Get:21 http://eg.archive.ubuntu.com/ubuntu xenial-updates/main Translation-en [218 kB] Get:22 http://eg.archive.ubuntu.com/ubuntu xenial-updates/main amd64 DEP-11 Metadata [298 kB] Get:23 http://eg.archive.ubuntu.com/ubuntu xenial-updates/main DEP-11 64x64 Icons [193 kB] Get:24 http://eg.archive.ubuntu.com/ubuntu xenial-updates/restricted amd64 Packages [7,776 B] Get:25 http://eg.archive.ubuntu.com/ubuntu xenial-updates/restricted i386 Packages [7,792 B] Get:26 http://eg.archive.ubuntu.com/ubuntu xenial-updates/restricted Translation-en [2,548 B] Get:27 http://eg.archive.ubuntu.com/ubuntu xenial-updates/restricted amd64 DEP-11 Metadata [157 B] Get:28 http://eg.archive.ubuntu.com/ubuntu xenial-updates/universe amd64 Packages [468 kB] Get:29 http://eg.archive.ubuntu.com/ubuntu xenial-updates/universe i386 Packages [453 kB] Fetched 847 kB in 6s (121 kB/s)                                                 Reading package lists... Done E: Failed to fetch http://eg.archive.ubuntu.com/ubuntu/dists/xenial-updates/main/binary-amd64/by-hash/SHA256/7ce67f72031f7cd7c4f24fffe8c90101935c8ae4e58502b1b60dfbb900f58841  Hash Sum mismatch E: Failed to fetch http://eg.archive.ubuntu.com/ubuntu/dists/xenial-updates/main/binary-i386/by-hash/SHA256/b4989c055e8da5afab24c96f86caf7157df19e46797e1217ad03a87d1b4a705a   E: Some index files failed to download. They have been ignored, or old ones used instead.   I have tried many solutions of similar related issue, but nothing worked for me :( Please help!  Edit: Solutions I found in Google that didn't work for me:
Whenever I click on software updater it says Failed to download repository information.  It's been saying this for the past few days now and I don't know why, my Internet connection is fine, I am able to manually download software.  Sometimes it crashes when I click okay, then attempts to look for updates again and gives me the same message.  Any ideas?  [EDIT] I just tried an answer posted where I reset where the downloads come from, but I was left with this message:  W:The repository 'http://ppa.launchpad.net/noobslab/noobslab-conky/ubuntu xenial Release' does not have a Release file.,  W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use.,  W:See apt-secure(8) manpage for repository creation and user configuration details.,  W:https://content.runescape.com/downloads/ubuntu/dists/trusty/InRelease: Signature by key AAC9264309E4D717441DB9527373B12CE03BEB4B uses weak digest algorithm (SHA1),  E:Failed to fetch http://ppa.launchpad.net/noobslab/noobslab-conky/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found,  E:Some index files failed to download. They have been ignored, or old ones used instead.
Need help to install persistent Ubuntu on USB drive Possible Duplicate:          I am a new user of Ubuntu. I would like to install a persistent Ubuntu 11.04 to my USB stick, and it should be able to work as a guest OS running on Windows so that I can boot it on other computers other than the one which I used for the installation. I have used several creators such as unetbootin, however from my understanding it can only create Live Linux which I am unable to save my configurations and files. If it's possible I would like to bypass the BIOS, that is to say that I can just load from the virtual machine without having to restart the computer. Thanks in advance!    Thanks for all the replies! Hi Mike, I am able to create a virtual machine and run it from my USB drive using a portable virtualbox. How do I go about from there, do I have to proceed with the installation? Could you elaborate more on the steps for the installation? Thanks again! Rigor in quantum field theory I'm trying to do something similar to this epsilon-delta graph I've found.  Specifically, I'd like to copy the placements and arrows, like the L+e and L-e coming out of L. Same thing with the x0 + d and x0-d coming out of the x0. Can someone help me with this? This is what I have so far.    \begin{tikzpicture} \begin{axis}[ ,         legend pos=north east,         axis x line=middle,         axis y line=middle,         x tick label style={/pgf/number format/fixed,                             /pgf/number format/fixed zerofill,                             /pgf/number format/precision=1},         y tick label style={/pgf/number format/fixed,                             /pgf/number format/fixed zerofill,                             /pgf/number format/precision=1},         grid = major,         width=8cm,           height=6cm,         grid style={dashed, gray!30},         xmin=0   ,     % start the diagram at this x-coordinate         xmax= 4,    % end   the diagram at this x-coordinate         ymin= 0,     % start the diagram at this y-coordinate         ymax= 11,   % end   the diagram at this y-coordinate %axis background/.style={fill=white},         xlabel=$x$,         ylabel=$f(x)$,         tick align=outside,         enlargelimits=false] % plot the stirling-formulae %\addplot[domain=0:200, red, ultra thick,samples=100] {K/(1 +    ((K-X0)/X0) * exp(r*x))    }; \addplot[domain=0:200, red, ultra thick,samples=100] {3*x-1 };  \addplot[line width=1pt, dashed, mark=none, black] coordinates {(0,8) (3,8)}; \addplot[line width=1pt, dashed, mark=none, black] coordinates {(3,0) (3,8)}; \addplot[line width=1pt, dashed, mark=none, blue] coordinates {(3.33,0) (3.333,9)}; \addplot[line width=1pt, dashed, mark=none, blue] coordinates {(2.666,7) (2.666,0)}; \addplot[line width=1pt, dashed, mark=none, blue] coordinates {(2.666,7) (0,7)}; \addplot[line width=1pt, solid, mark=none, blue] coordinates {(3.333,9) (0,9)}; \addplot[holdot] coordinates{(60,8.66)};  % 1\addlegendentry{$f(x) = 10 \sin (x)$}  \end{axis}   \end{tikzpicture}   which gives How to render lightning in Cycles How can you render a lightning bolt using Cycles? Relativistic Mass and Dark Matter In a question  Ron Maimon comments that "relativistic mass makes gravity, not rest mass."  If so, does that mean that the faster that stars orbit the galaxy the larger the relativistic mass of the galaxy therefore more gravity therefore the stars orbit even faster therefore the gravity gets even more therefore the stars keep on getting faster ...  So the speed of stars and mass of galaxy would be correlated with age and history of the galaxy or galaxy clusters and that's why calculations of galaxies' masses don't add up. Is true that $\sum_{k=1}^n\frac{[kx]}{k}\leq[nx]$, for every $x\in\mathbb{R}$ and for every $n\in\mathbb{Z}^+$? Is true that $\displaystyle\sum_{k=1}^n\dfrac{[kx]}{k}\leq[nx]$, for every $x\in\mathbb{R}$ and for every $n\in\mathbb{Z}^+$?  My work:  Let $x\in\mathbb{R}$ be given. For every $k=1,\dots,n$, define $i_k\in\{0,1,\dots,k-1\}$ such that  $$ [x]+\frac{i_k}{k}\leq x&lt;[x]+\frac{i_k+1}{k}\hspace{20mm} (*). $$  On one hand, we have that $[kx]=k[x]+i_k$ for every $k=1,\dots,n$.  So  $\displaystyle\sum_{k=1}^n\dfrac{[kx]}{k}=n[x]+\displaystyle\sum_{k=1}^n\dfrac{i_k}{k}=[nx]+\displaystyle\sum_{k=1}^n\dfrac{i_k}{k}-i_n$  Thus  $$\displaystyle\sum_{k=1}^n\dfrac{[kx]}{k}\leq[nx]\Leftrightarrow\displaystyle\sum_{k=1}^n\dfrac{i_k}{k}\leq i_n\,.$$  On the other hand, from $(*)$ is direct that $i_k=[k(x-[x])]$. Thus  $$\displaystyle\sum_{k=1}^n\dfrac{[kx]}{k}\leq[nx]\Leftrightarrow\displaystyle\sum_{k=1}^n\dfrac{[k(x-[x])]}{k}\leq [n(x-[x])]\,.$$  In other words, we can assume that $x\in[0,1)$.   Now the questions is:  Is true that $\displaystyle\sum_{k=1}^n\dfrac{[kx]}{k}\leq[nx]$, for every $x\in[0,1)$ and for every $n\in\mathbb{Z}^+$?  Any simpler approach? Any thoughts? How to start/stop/restart a thread in Java? An image alt="" text should contain information about that image in the context of the page, so for instance if you have an article about cats on skateboards and then a photograph of the cat on his skateboard you'd probably give it the alt text of alt="Fluffy pulling some mad tricks on his pimped-out board".          &ndash; Wireframes created with   However, what should happen when that image is a link to a page (such as the Wikipedia cat page)?  I don't think there is any point using the title attribute here because screenreaders just ignore that when an alt attribute exists - the only people who would see the title attribute are mouse users who hover over the image, so that excludes keyboard only users too. It's not really any benefit to accessibility to include a title in this situation (Overall the title attribute is a bit useless really).  So, what should the image ALT text say in this case?   states:     Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.    Therefore giving it the alt text of cat article page on Wikipedia is incorrect because that doesn't describe the image, neither does skateboarding cat image that links to the wikipedia article because the alt text should refer to the image itself, not the link associated with it. I am travelling to Calgary from Delhi. I have an Air India flight from Delhi to Dubai then British Airways flight from Dubai to London and Air Canada flight from London to Calgary. My query is "Do I require a transit visa." Plz help as I am travelling in four days Why can I use a function before it's defined in JavaScript? Why Are Ethernet/RJ45 Sockets Magnetically Coupled? As the title says really, why do ethernet sockets need to be mag-coupled? I have a basic understanding of electronics, but mostly, I can't figure out the right search terms to google this properly. Cannot invoke method or retrieve property from null object. Object returned by the following call stack is null. \"File\r\n\" Cannot set up multiple desktops (workspaces) Why does switching to the tty give me a blank screen? After booting to the GUI in 12.04, I attempt to move to the virtual terminal (or shell, or tty) via Ctrl-Alt-F1 (F1 through F6), and the screen remains blank. I have tried all 6 tty instances and the results are the same. Ctrl-alt-F7 brings me back to the GUI without a problem. Any thoughts? How can I restart a Windows 7 computer without screen or mouse? I've recently had problems with my work computer not recognizing either of its attached screens.  I've also had problems with my home computer "locking" the mouse to one app, and no longer acknowledging clicks on, say, the start menu.  In both cases the computer is still running, and I can close apps and so forth with the keyboard.  Restarting usually addresses the problem.  What's the simplest way to restart a Windows 7 computer by the keyboard alone?  Something consistent across all versions would be super.  In Win XP, I believe it was Ctrl-Alt-Delete; pause; Alt-R for Restart; Enter to select.  But on 7 Ctrl-Alt-Delete no longer brings up the same menu.  I'd use Ctrl-Alt-Esc for the Task Manager, but it no longer has a Restart menu (at least on Win 7 Home). Would a Cup of Tea Be Hotter If you Add the Milk Before or After Boiling Water? This is a bit of dispute between work colleagues. An answer would be greatly appreciated.  My argument is as follows:  If you add X amount of milk at a temperature of M to a mug at room temperature R before adding X amount of water at temp W, the result would be a cooler cup of tea than if you'd added the hot water first. This would be due to the milk reducing the overall temperature of the mug in the time that has been in it resulting in the addition of boiling water having less of an effect and resulting in a slightly cooler cup of tea/coffee.   Conversely, if you add the hot water first, due to the mug being heated, the effect of adding the cool milk will be less and therefore the end result will be a hotter cup of tea.  My Colleagues arguement is simply that it would not make a difference but without any form of justification.   If anyone can give real scientific light to this issue it would be greatly appreciated :) Non-Exchange address in Exchange GAL We just made the switch to Google Apps for part of our domain. We disabled the accounts that are now on Google Apps and mail routes correctly. Our problem is that now we have no way of seeing those users in the Global Address List.  So we have these users in our Active Directory, they have no mailbox on Exchange, and we want to be able to see/search for their addresses in the GAL. Is there any way to do this?  This is Exchange 2007, if that matters. I recently made changes to my fstab file and, upon reboot, noticed I had an error in it. I get the typical mount error on boot. I went to try and modify it by entering the read-only mode but then, since it's read only, I can't access it. Is there a way around this or some way to delete the file so I can use the backup (which I'm pretty sure works)? One of us is wrong, aren't we? I have just learned from what I consider a reliable source, that the following sentence is correct:     One of us is wrong, aren't we?   I would never in my life have written this, but I am assured that   As I realize comments don't live forever I will quote the relevant parts:     oerkelens : So you  would really write One of us is wrong, aren't we? I guess by analogy you would not bat an eyelid at One of these balls is blue, aren't they?   Matt Эллен : yes, "Then one of us is wrong, aren't we?" is exactly how it would be written. Same for the balls.   Could someone please enlighten me how it is possible that the number in a question tag supposedly has to be in discordance with the subject of the main clause?  I admit that I am not the youngest any more, and my school days are long gone, but back in the days, I was taught that  1. a verb and its subject concord in number 2. a question tag concords with the subject of the main clause  I was given examples like:     It is warm today, isn't it?   We will be on time, won't we?   Mary is pretty, isn't she?   John isn't the brightest, is he?   Some people may notice that the subject of the main clause seems to determine every time the subject of the question tag. When the main clause subject is singular, so are verb and subject in the question tag.  I was under the impression that a) this made sense and b) this would be a general rule.  I fully realize that grammar does not have to make sense, so a) is immaterial. As for b), today I learned I was wrong :)  So when (and possibly why?) do we form question tags that are different in number from their main clause?   To exemplify, also the other example sentence that I used and was corrected on:     One of these balls is blue, isn't it? (so this is wrong)   One of these balls is blue, aren't they? (and this is correct)   As an afterthought, does this strange grammatical number mix-up only appear in question-tags, or should I always refer to singular subjects in the plural if certain conditions are met? And what are those conditions?  Which versions are correct?     One of the cars is broken, aren't they? They (the car(s?) that is(are?) broken) should be fixed.   One of the cars is broken, aren't they? It (the car that is broken) should be fixed.   One of us must be wrong, mustn't we? We (the one(s?) that is (are?) wrong) should make amends.   One of us must be wrong, mustn't we? He (the one that is wrong) should make amends.   (In the last one, they could of course be used as the singular they, but that would avoid the issue...) The space obtained by identifying the antipodal points of a circle