While trying to create a new  file in php I granted ownership permission to www-data. There onwards I can't login to the superuser session but I can login to the guest session. The login screen asks for password and on typing password thereafter it redisplays the screen. What to do?
My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M
First, my apologies if this has already been asked/answered.  I wasn't able to find this question via search.  My question comes from Rudin's "Principles of Mathematical Analysis," or "Baby Rudin," Ch 1, Example 1.1 on p. 2.  In the second version of the proof, showing that sets A and B do not have greatest or lowest elements respectively, he presents a seemingly arbitrary assignment of a number $q$ that satisfies equations (3) and (4), plus other conditions needed to show that $q$ is the right number for the proof.  As an exercise, I tried to derive his choice of $q$ so that I may learn more about the problem.  If we write equations (3) as $q = p - (p^2 - 2)x$, we can write (4) as   $$ q^2 - 2 = (p^2 - 2)[1 - 2px + (p^2 - 2)x^2]. $$  Here, we need a rational $x &gt; 0$, chosen such that the expression in $[...]$ is positive.  Using the quadratic formula and the sign of $(p^2 - 2)$, it can be shown that we need   $$ x \in \left(0, \frac{1}{p + \sqrt{2}}\right) \mbox{ for } p \in A, $$  or, for $p \in B$, $x &lt; 1/\left(p + \sqrt{2}\right)$ or $x &gt; 1/\left(p - \sqrt{2}\right)$.  Notice that there are MANY solutions to these equations! The easiest to see, perhaps, is letting $x = 1/(p + n)$ for $n \geq 2$.  Notice that Rudin chooses $n = 2$ for his answer, but it checks out easily for other $n$.  The Question:  Why does Rudin choose $x = 1/(p + 2)$ specifically?  Is it just to make the expressions work out clearly algebraically?  Why doesn't he comment on his particular choice or the nature of the set of solutions that will work for the proof?  Is there a simpler derivation for the number $q$ that I am missing? Why don't the colonists wear spacesuits in Alien: Covenant? In the beginning of the Alien: Covenant movie, a group of colonists from the main ship make a landing on an unknown planet, which they found out accidentally after ship has been bombarded by an unknown wave from a star collapse and what bothers me, is that they don't wear any spacesuits, any protective gear, any air filter systems, just nothing.  Is that really the way future space expeditions gonna explore new possible planets presumed as possible habitable homes for humanity?  Every 5th grader knows, from the biology school lessons, that water, air, and even earth itself contains and gives life to a thousands of viruses, bacteria, and microorganisms.  You can breathe in bacteria, or virus, and be dead in a seconds.  Do film makers really suppose we will take it as realistic depiction of extraterrestrial expedition?   Reality check just screams out loud.  What do you think can be their motivation for such a decision? Is it better in C++ to pass by value or pass by constant reference? The question of  made me wonder as to whether wizards, any of them, do practice religion. Whether there be magic-person only religions or shared muggle faiths, I do not recall any wizards (born in the wizard world anyway) saying that they did practice a religion.  Many of them do celebrate Christmas, but as was commented on the above linked question, there are many non-christian muggles that also observe Christmas. So I am not sure that can be an accurate identifier. Answering this question may link into identifying . What is the best way to give a C# auto-property an initial value? When reading about  on the OALD, I saw the following note:     The difference between someone and anyone is the same as the difference between  and . Look at the notes there.   The note that I read for some is the following:     In negative sentences and questions any is usually used instead of some:           I don't want any more vegetables.     Is there any wine left?           However, some is used in questions that expect a positive reply:           Would you like some milk in your coffee?     Didn't you borrow some books of mine?      Does that apply to someone too? Should I use someone in a question when I am expecting a positive answer?      Does someone know the answer? Is there a way to run Python on Android? We are working on an  version and this platform has a nice Python API..  However, there is nothing official about Python on Android, but since  exists, is there a way to let the snake and the robot work together?? avidemux problems with Ubuntu 16.04 LTS I installed 16.04 a few days ago and had to reinstall some apps. One of them was avidemux. After I installed it from the Software Center, I couldn't get it to work properly. It wouldn't even load a video clip before giving me an error message and closing.   After trying many commands to purge the avidemux files, I still can't get it to reinstall from the Software Center...   Any tips? .NET Casting Generic List Google App Engine: Is it possible to do a Gql LIKE query? With all the new sites up and running it gets more and more difficult for users to really know the scope of a site and thus a lot of questions a migrated to places where they are (probably even more) off-topic, see e.g. . So I request the opposite of :  Allow migration if you have enough rep on both the source and the target site (the target reputation required could be a bit lower, say 5001)  That way questions could only be migrated by users familiar with the scope of both sites who can really estimate where the question is better. Maybe those who don't have the rep on the target site could still be able to cast a flagging-only-but-not-counting-as-vote vote...  1) Courtesy of I know that the -f means --fix-broken from the manual and that it attempts to fix problems with the packages, but what exactly does? How it decides how to fix the packages or if they need fixing and the method of fixing? And why sometimes it fails? vinegar pickles safety How to receive sms from our android app? I'm looking for an elegant way to show that, among non-negative numbers, $$ \max \{a_1 + b_1, \dots, a_n + b_n\} \leq \max \{a_1, \dots, a_n\} + \max \{b_1, \dots, b_n\} $$  I can show that $\max \{a+b, c+d\} \leq \max \{a,c\} + \max \{b,d\}$ by exhaustively checking all possibilities of orderings among $a,c$ and $b,d$.  But, I feel like there should be a more intuitive/efficient way to show this property for arbitrary sums like the one above. redirecting openshift rhcloud domain to custom domain for SEO purposes Openshift application url: example.rhcloud.com  Custom domain: example.com  I came across this  and added the redirection rule. However, I can not access example.rhcloud.com now. My custom domain is www.example.com.  To avoid duplicate content problems, I tried this redirection.   Here is my .htaccess file:  RewriteEngine on   # Uncomment the following lines to force HTTPS #RewriteCond %{HTTP:X-Forwarded-Proto} !https  #RewriteRule .* https://%{HTTP_HOST}%{REQUEST_URI} [R,L]   # WordPress Defaults RewriteBase / RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L]  # Redirect Https traffic to Http RewriteEngine on  RewriteCond %{SERVER_PORT} ^443$ [OR] RewriteCond %{HTTPS} on RewriteRule  ^(.*)$ http://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]   # Redirect non-www to www RewriteEngine on  RewriteCond %{HTTP_HOST} !^www\. [NC] RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]    # Redirect openshift rhcloud domain to custom domain RewriteEngine on  RewriteCond %{HTTP_HOST} ^example.rhcloud.com$ RewriteRule (.*)$ http://www.example.com/$1 [R=301,L]   Why is example.com not redirecting to ww.example.com? How do I fix this?  Also, I see that since I have https to http redirection and non www to www redirection, my blog has been loading slow. How can I reduce it to lesser number of rules?  Edit:  In chrome:   In Firefox:     The page isn't redirecting properly, Firefox has detected that the server is redirecting the request for this address in a way that will never complete.     This problem can sometimes be caused by disabling or refusing to accept cookies. Is there a human home planet? Did all the humans in the Star Wars universe originate on a single planet some time in the distant past, or did they originate on different worlds and intermix into one species over millenia?  This is specifically about only humans, not humanoid aliens. I would prefer answers from the main canon or EU canon. How do ability score improvements improve modifiers? First time player in a group figuring out things as we all go.  I just hit level four as a Ranger, and I get to improve one ability score of my choice by 2, or I can increase two ability scores of my choice by 1.  My first thought was Strength, as I've been rocking a score of 11 with a mod of +0 so far. But I read that Rangers use (wisdom mod + 10) for their spell casting modifier. Currently my wisdom is 13, with a mod of +1. If I increase either STR or WIS, will the modifier increase as well? How and why?  A Monk in our party went from 9 CON to 11 during their ability score improvement, and by doing so their modifier went from −1 to 0.  We're all pretty new, so between eight people we're currently sharing one book, and all trying to locate our own copies for later campaigns. That's making it… inefficient for us to learn these things quickly. In PHP you can do:  print_r($var) or vardump($var)   which prints "human-readible" information about variable.  Is there equivalent functions / helpers for those in Ruby / Rails ? How to use variable inside parameter $_GET? example: ($_GET[$my_var])