I'm trying to install the most stable, boring version of GIMP available, without adding special repositories. I'm assuming the correct way to do this is sudo apt install gimp. Unfortunately, I'm getting the following warning:  WARNING: The following packages cannot be authenticated!   libbabl-0.1-0 libsdl1.2debian libamd2.4.1 libcamd2.4.1 libccolamd2.9.1   libcholmod3.0.6 libumfpack5.7.1 libgegl-0.3-0   Should this be happening? I tried running  sudo apt-key update sudo apt-get update   which didn't fix the issue. What should I do?  Edit: Here is the full output of sudo apt install gimp:  Reading package lists... Done Building dependency tree        Reading state information... Done The following packages were automatically installed and are no longer required:   libmircommon5 linux-headers-4.4.0-78 linux-headers-4.4.0-78-generic   linux-headers-4.4.0-79 linux-headers-4.4.0-79-generic   linux-image-4.4.0-78-generic linux-image-4.4.0-79-generic   linux-image-extra-4.4.0-78-generic linux-image-extra-4.4.0-79-generic   linux-signed-image-4.4.0-78-generic linux-signed-image-4.4.0-79-generic   linux-tools-4.4.0-78 linux-tools-4.4.0-78-generic linux-tools-4.4.0-79   linux-tools-4.4.0-79-generic Use 'sudo apt autoremove' to remove them. The following additional packages will be installed:   gimp-data libamd2.4.1 libbabl-0.1-0 libcamd2.4.1 libccolamd2.9.1   libcholmod3.0.6 libgegl-0.3-0 libgimp2.0 libsdl1.2debian libumfpack5.7.1 Suggested packages:   gimp-help-en | gimp-help gimp-data-extras The following NEW packages will be installed:   gimp gimp-data libamd2.4.1 libbabl-0.1-0 libcamd2.4.1 libccolamd2.9.1   libcholmod3.0.6 libgegl-0.3-0 libgimp2.0 libsdl1.2debian libumfpack5.7.1 0 upgraded, 11 newly installed, 0 to remove and 0 not upgraded. Need to get 14.0 MB of archives. After this operation, 79.8 MB of additional disk space will be used. Do you want to continue? [Y/n] y WARNING: The following packages cannot be authenticated!   libbabl-0.1-0 libsdl1.2debian libamd2.4.1 libcamd2.4.1 libccolamd2.9.1   libcholmod3.0.6 libumfpack5.7.1 libgegl-0.3-0 Install these packages without verification? [y/N] n E: Some packages could not be authenticated   EDIT: I don't believe this question is a duplicate of any of the questions suggested by reviewers:    None of the answers are the one that worked for me.  Does not have the answer that worked for me.  This is not the error I got initially.
I'm experimenting with VPNs, so I wanted to install pptpd.  john@desktop:~$ sudo apt-get install pptpd [sudo] password for john:  &lt;snip&gt; The following extra packages will be installed:   bcrelay The following NEW packages will be installed:   bcrelay pptpd 0 upgraded, 2 newly installed, 0 to remove and 11 not upgraded. Need to get 90.5 kB of archives. After this operation, 442 kB of additional disk space will be used. Do you want to continue [Y/n]? y   And everything runs fine until I get down to here:  WARNING: The following packages cannot be authenticated!   bcrelay pptpd Install these packages without verification [y/N]? n E: Some packages could not be authenticated   No authentication?  I'm no security expert, but I'm fairly sure that's a bad thing.  So I .  john@desktop:~$ apt-cache policy pptpd pptpd:   Installed: (none)   Candidate: 1.3.4-3ubuntu1   Version table:      1.3.4-3ubuntu1 0         500 http://us.archive.ubuntu.com/ubuntu/ natty/main i386 Packages john@desktop:~$ apt-cache policy bcrelay bcrelay:   Installed: (none)   Candidate: 1.3.4-3ubuntu1   Version table:      1.3.4-3ubuntu1 0         500 http://us.archive.ubuntu.com/ubuntu/ natty/main i386 Packages   They're coming from Ubuntu.com and not being properly authenticated?  What's going on here?
I tried to find an answer to this a few years ago, but it seemed it wasn't possible then (I suspect it isn't now either! - but what the hell!)   I have a three monitor system, that I mostly use for remote desktop. However occasionally it would be useful to have remote desktop on two monitors and use the other monitor for the local machine.   I know it is possible to have a single monitor full screen, or to stretch an RDP session across monitors, but this loses things like snapping etc.   P.S. this is a duplicate of  thread, but that was a couple of years ago, I'm hoping things have changed. Road Front Derailleur / Shifter Tuning I've recently converted into 2spd crankset so I've bought a new 2spd road lever. I'm really struggling now to tune the front derailleur. Could you please assist me by answering this questions:   Why the shifter does 2 clicks instead of 1 when you go up? Is that normal? It's 2spd shifter isn't it supposed to have only 1 click? And at the same time ... When I do one click up with the shifter the derailleur moves but always seems like not far enough so I need go up for another click, which leads to ... When I try to go down the gears and I release the shifter that was clicked 2 times it goes all 2 click at once and the derailleur makes this ugly very loud clutch back to the first gear. It doesn't sound right at all.   Can you tell me what am I doing wrong here? I guess I'm missing something very important here, but I don't know exactly what.  I watched bunch of youtube instructions on how to properly tune a front derailleur, but I still facing the same problem over and over again.  Thank you in advance, and please ask if the question is not clear enough. How get the :hover css style of an anchor with jQuery? How can i get the :hover in css stylesheet on the fly with jquery?  stupid example:   a.foo {     color: red;     font-size: 11px; }  a.foo:hover {     color: blue;     font-size: 12px;  }   how to retrieve that color and font-size before that mouse will go over the anchor? Any good tutorials for learning how to post-process images? I don't really know where to start with post-processing my images. I normally just straighten, crop and sharpen. Do people know of any good resources on the internet for getting a grip with Photoshop and similar tools? Conditional typesetting / build Let's say I have .tex file which is a set of problems and solutions, of which I want to make two pdf files, one which includes the solutions and one which doesn't. so I need to build the .tex file under two different modes, and specify that parts of the document be ignored under one of the modes.  This is something common in programming context. e.g. in C++ i can code  #ifdef DEBUG   // do this additional stuff ... #endif   How can I do something equivalent in latex? Understanding DNA match of 1,723 cM I have a DNA match of 1,723 cM with a male 6 years younger than me. His father is one of a twin, could my match be not my half-sibling but my 1st cousin. Headers and font in KOMA-script I am setting up the layout for my bachelor thesis using scrbook as basis for a self-made documentclass with twosided print. I want a header containing the current part number and name on the outer side (left on even pages, right on odd pages), the current chapter number and name on the center of the head and the same for section on the inner side. I found this example in the KOMA-Script documentation:  \usepackage{scrlayer-scrpage} \pagestyle{scrheadings} \automark[chapter]{chapter} \automark*[section]{}   It puts the chapter on the outer side on even pages and the section on the outer side on odd pages. Sadly, I was not able to modify this to fit my needs because I do not really understand the way KOMA-Script works here. If a part starts but there is still no chapter in it, the place for the chapter shall remain empty (same for chapter and section). Can anyone help?  Furthermore, I would like to change all fonts that KOMA-Script changes (e.g. toc, section, chapter...) back to the default computer modern as I do not like the font KOMA-Script uses here. Is there a better way than changing all the fonts manually like this:  \addtokomafont{section}{\fontfamily{cmr}\selectfont} How do I know if I'm working on a Virtual Machine or not? Is there a way to know if the Windows machine I'm working on is virtual or physical? (I'm connecting with RDP to the machine. If it's a virtual machine it is working and handled by VMWare). Shortcode display outside the div I have created a shortcode that retrives and displays a form.The content of the attribute in HTML.   function check_my_login( $atts)     {          return '&lt;form action="" name="" method="post" enctype="multipart/form-data"&gt;                &lt;div class="form-group"&gt;                     &lt;label for="description"&gt;Project Description&lt;/label&gt;                     &lt;textarea name="p_description" placeholder="Project Description" class="form-control"&gt;&lt;?php if (isset($_POST['p_description']) &amp;&amp; $_POST['p_description'] != '') echo $_POST['p_description'] ?&gt;&lt;/textarea&gt;                 &lt;/div&gt;                  &lt;div class="form-group"&gt;                     &lt;label&gt;Project Attachment&lt;/label&gt;                     &lt;input type="file" name="p_attachment"&gt;                 &lt;/div&gt; &lt;/form&gt;';     }     add_shortcode( 'kentaUser', 'check_my_login' );   Now use this shortcode inside the Post/page.   Like this    &lt;div class='manage_page'&gt;[kentaUser]&lt;/div&gt;  But my shortcode content display out side the div.Display upper side in post/page content.  &lt;div class='manage_page'&gt;&lt;/div&gt;    Any one short out this problem. How do I setup user autostart and properly configure systemd user services? On my arch server, I was setting up users restricted to their home directories. I ran:  useradd -m -s /bin/bash username and passwd username  I've read   I figured I should use systemd user services to make each user run a node server on startup. So i logged into one user account su username and created a file ~/.config/systemd/user/serve.service containing:  [Unit] Description=One of the servers  [Service] ExecStart=/usr/bin/node /home/username/server.js  [Install] WantedBy=default.target   then I ran systemctl --user enable serve.service which responded with Failed to connect to bus: Permission denied  As far as I understand I should run systemctl --user ... command logged in as a user and not as root.  So what did I miss in this configuration? So I finally killed the Ender Dragon! As I was climbing the portal back to the world, I noticed that on top of the column there was an egg. So I attacked, mined, clicked and nothing happened, it just teleported away. What does the egg do and how do I get it? If $a,b$ are the roots of the equation $2 x^2 -3 x +1 = 0$, find an equation whose roots are $a/(2b +3)$, $b/(2a +3)$ If $a,b$ are the roots of the equation $2 x^2 -3 x +1 = 0$, find an equation whose roots are $a/(2b +3)$, $b/(2a +3)$   I was practicing quadratic equation questions online but I am stuck on this question.  I found the values of roots $a= 1$, $b= 1/2$ Following my question , I am wondering if there are strong views for or against the use of standard deviation to detect outliers (e.g. any datapoint that is more than 2 standard deviation is an outlier).  I know this is dependent on the context of the study, for instance a data point, 48kg, will certainly be an outlier in a study of babies' weight but not in a study of adults' weight.  Outliers are the result of a number of factors such as data entry mistakes. In my case, these processes are robust.   I guess the question I am asking is: Is using standard deviation a sound method for detecting outliers? What prevents this magnetic perpetuum mobile from working? Does the cross-entropy cost make sense in the context of regression? Does the cross-entropy cost make sense in the context of regression (as opposed to classification)? If so, could you give a toy example through TensorFlow? If not, why not?   I was reading about cross-entropy in  by Michael Nielsen and it seems like something that could naturally be used for regression as well as classification, but I don't understand how you'd apply it efficiently in TensorFlow since the loss functions take logits (which I don't really understand either) and they're listed under classification So I tried a few different answers that I found here, and I feel that this is possibly a duplicate question, but everything I have tried from the other solutions hasn't worked.  Basically I am trying to bake a material to a texture that will be used in Unity, but every test gives me a black background image.  In the image below, the top image texture is the mask (black and white, white being the leaves), and the bottom image texture is the colour. Changing precision on a column in the attribute table without losing data? I have data in an Excel file that I want to join with a shapefile in my project. The Excel file contains values like volumes. The Excel file and the shapefile I want to join it with both contain the same property names.  The problem is, when I join the two, I get too many decimals in the attribute table. I get six, but I only want it to be one.  I tested to change the format of the cells to one decimal, and then I saved the file as *csv. But, somehow I seem to loose data in the process? It should be 42 rows that contains data in the column i am working with, but I end up with only like 10?  Another thing is that my property names contains the letters Å. Ä and Ö, perhaps this complicates things?  I read the question , but it doesn't mention the problem with the data loss.  My question was tagged with , but I didn't write what version I'm using. I use QGIS 2.2.0. Would it help to upgrade to the latest version? I understand that the  is given by  $$F^{\mu\nu}\mapsto\begin{pmatrix}0 &amp; -E_{x} &amp; -E_{y} &amp; -E_{z}\\ E_{x} &amp; 0 &amp; -B_{z} &amp; B_{y}\\ E_{y} &amp; B_{z} &amp; 0 &amp; -B_{x}\\ E_{z} &amp; -B_{y} &amp; B_{x} &amp; 0 \end{pmatrix}$$  where $\mu$, $\nu$ can take the values {0,1,2,3} or {$t,x,y,z$}.  So, for example  $$F^{01}=F^{tx}=-E_x$$  My question is, what would the following expression be?  $$F^{t\rho}=?$$ or $$F^{z\rho}=?$$  where $\rho=\sqrt{x^{2}+y^{2}}$ is the radial coordinate in ?  And more generally, how can we construct the Electromagnetic Tensor in cylindrical coordinates? Where $\mu$, $\nu$ now take the values {$t,\rho,\varphi,z$}. How do I choose a macro lens for a Canon APS-C camera? What are the most widely used C++ vector/matrix math/linear algebra libraries, and their cost and benefit tradeoffs?