X Windows special programs: do some of these still exist? Which ones?
X Windows special programs: do some of these still exist?
I recently made the switch to Ubuntu. Everything on my laptop works fine except my hybrid graphics card. It is Intel graphics combined with Nvidia GeForce GT650M. I tried Bumblebee, but primusrun doesn't work (segmentation fault, core dumped) and optirun works with glxspheres64, but steam games look worse with optirun than with Intel graphics (e.g. Surgeon Simulator 2013 runs fine with Intel and hangs a lot with optirun)   I tried Nvidia Prime, but it gives me a black screen on startup after install, so I can't do anything and have to power off my PC with the power button. I also tried nvidia-prime 0.5 on Ubuntu 14.04, and then I get 'low-graphics mode' and I can't get to Unity. Classify all groups with order $pq$, $p$ is not equal to $q$ I am reading the following material:  . At page 5, there is a proof classifying all groups with order $pq$(they are all primes and $p$ is not equal to $q$). I am lost in the last two sentence, which claims the semidirect product are all isomorphic. Could someone help me to understand it? Thanks! I looking for help with proving the following inequality. Any relevant logarithmic identities would be great. Tried differentiating and taking limits and I'm lost as to how to approach this.   $$\frac 1{x+1}&lt;\ln\left(\frac{x+1}x\right)&lt;0.5\left(\frac 1x+\frac 1{x+1}\right)$$ Completeness and Incompleteness I'm trying to figure out how to assign higher priority to one PPA over another PPA. I had a look on bunch of the answers on this forum but none of them solves my problem.  We have two PPA sources on some of our servers which we stick into separate files in /etc/apt/sources.list.d . Some of these repos provide same packages (in terms of names) but different versions and possibly different binaries. Is there a way how we can PRIORITISE one repo over another ?  I read apt_preferences tutorial but it could not be more obscure and didn't find the answers for my question. Here is the situation. WE have the following sources:  $ ls -l /etc/apt/sources.list.d  total 12 -rw-r--r-- 1 root root 66 Jan  2 16:50 nginx-source.list -rw-r--r-- 1 root root 84 Jan  2 16:49 ruby-ng-experimental-source.list   where nginx-source.list content is:  deb     http://ppa.launchpad.net/nginx/stable/ubuntu precise main   and ruby-ng-experimental-source.list content is:  deb     http://ppa.launchpad.net/brightbox/ruby-ng-experimental/ubuntu precise main   Both of these sources provide nginx-full package of different versions etc. When I list the priorities ruby-ng-experimental-source.list is on top of output hence nginx-full is installed from that repo:  $ apt-cache policy nginx-full                                  nginx-full:   Installed: 1:1.2.3-1~38~precise1   Candidate: 1:1.2.6-1~43~precise1   Version table:      1:1.2.6-1~43~precise1 0         500 http://ppa.launchpad.net/brightbox/ruby-ng-experimental/ubuntu/ precise/main amd64 Packages  *** 1:1.2.3-1~38~precise1 0         100 /var/lib/dpkg/status      1.4.1-1ppa0~precise 0         500 http://ppa.launchpad.net/nginx/stable/ubuntu/ precise/main amd64 Packages      1.1.19-1ubuntu0.1 0         500 http://mirror.rackspace.co.uk/ubuntu/ precise-updates/universe amd64 Packages      1.1.19-1 0         500 http://mirror.rackspace.co.uk/ubuntu/ precise/universe amd64 Packages   How do I prioritize repo listed in nginx-source.list over the one which is on top of the list now ? I tried something like this:  $ cat /etc/apt/preferences Package: nginx-full Pin: origin http://ppa.launchpad.net/nginx/stable/ubuntu Pin-Priority: 1000  Package: nginx-full Pin: origin http://ppa.launchpad.net/brightbox/ruby-ng-experimental/ubuntu Pin-Priority: 100   But that has changed priorities of both sources to the same number - or something like that ? So this has NOT changed the priorities and nginx-full is still being installed form the brightbox PPA  $ apt-cache policy nginx-full   nginx-full:   Installed: 1:1.2.3-1~38~precise1   Candidate: 1:1.2.6-1~43~precise1   Package pin: (not found)   Version table:      1:1.2.6-1~43~precise1 1000         500 http://ppa.launchpad.net/brightbox/ruby-ng-experimental/ubuntu/ precise/main amd64 Packages  *** 1:1.2.3-1~38~precise1 1000         100 /var/lib/dpkg/status      1.4.1-1ppa0~precise 1000         500 http://ppa.launchpad.net/nginx/stable/ubuntu/ precise/main amd64 Packages      1.1.19-1ubuntu0.1 1000         500 http://mirror.rackspace.co.uk/ubuntu/ precise-updates/universe amd64 Packages      1.1.19-1 1000         500 http://mirror.rackspace.co.uk/ubuntu/ precise/universe amd64 Packages   Anyone has any idea how to achieve what I'm trying to do ? Form inside a table "What kind of a person" vs. "what kind of person" Subsample of a random sample: random sample? How can I implement "cut outs" for lighting in OpenGL? Command for argmin or argmax? How can you get the argmin or argmax in Latex? Two solutions I found are:  \underset{x}{\operatorname{argmax}}   \DeclareMathOperator*{\argmin}{arg\,min}   Any other ideas?  [1]   [2] Mysterious cord running from wall. Safe? Where to find structure of objects that I can access in PHP snippets added to different parts of UI? Either fix edit preview display to render bare links to more than five sites just like the post renderer, or convert all links Have Chrome autodetect language before spelling checking? How to Redirect Pages with Query String? I want to Redirect as seen below:  https://example.com/p1/p2?sort=p.model&amp;order=ASC&amp;page=2   to  https://example.com/p3/p4?sort=p.model&amp;order=ASC&amp;page=2   Also, I have this code in my .htaccess file :  RedirectMatch 410 ^/p1/p2&amp;   I have used below code, but I just see 410 code for that URL :  RewriteRule ^/p1/p2?sort=p.model&amp;order=ASC&amp;page=2$ /p3/p4?sort=p.model&amp;order=ASC&amp;page=2 [QSD, R=301,L]   So, I have changed RedirectMatch 410 ^/p1/p2&amp; to Redirect 410 ^/p1/p2&amp; , but this time I have seen 404 Code for my Request URI. What should I do? What is the tolerable magnetic field (in Tesla) for a hard disk? I was wondering what would be the safest magnetic field for a hard drive so that the data inside it is safe and not wiped off?  For example I have a 2.1 home theatre system and when I take my android phone near it to check the magnetic field range it gives me a reading of 1000 micro Tesla. Would that be considered safe for a nearby hard disk? Syntax error while defining an array as a property of a class Can I purge configuration files after I've removed the package? I was doing a package removal with apt-get remove but then realized I should have done a --purge along with it to remove the configuration files.  Can I remove the packages configuration files easily or do I need to reinstall the package and then remove with a --purge? How do I survive in the Underworld? How can I serialize an object to JSON without properties that are null? To communicate with a REST interface on a private system, I need to send a JSON message from a trigger. I have a message object that has some fields, lists and a child object:  public class MerchantConfig {  public class MIDConfig {     public String mid;     public String currencyCode;     public String cardTemplateName;     public String paymentPanelRestriction;     public List&lt;String&gt; restrictedCountries;      public String paymentPanelRestrictionForCountries; }  public String merchantName; public String sopgTemplateName; public Integer dispositionTimeWindowInMinutes; public List&lt;String&gt; features; public Boolean activateImmediately; public List&lt;MIDConfig&gt; midConfiguration; }   I can serialize it to JSON using the built-in serializer:  String body = JSON.serializePretty([MerchantConfig instance]);   The result:  {   "sopgTemplateName" : null,   "midConfiguration" : [ {     "restrictionCountries" : [ "DE", "AT" ],     "paymentPanelRestrictionForCountries" : "MANDATORY",     "paymentPanelRestriction" : "OPTIONAL",     "mid" : "1000000001",     "currencyCode" : "EUR",     "cardTemplateName" : null   }, {     "restrictionCountries" : [ ],     "paymentPanelRestrictionForCountries" : "",     "paymentPanelRestriction" : "OPTIONAL",     "mid" : "1000000002",     "currencyCode" : "USD",     "cardTemplateName" : null   }, {     "restrictionCountries" : [ ],     "paymentPanelRestrictionForCountries" : "",     "paymentPanelRestriction" : "PROHIBITED",     "mid" : "1000000003",     "currencyCode" : "AUD",     "cardTemplateName" : null   } ],   "merchantName" : "Test Merchant",   "features" : [ XYZ ],   "dispositionTimeWindowInMinutes" : 10,   "activateImmediately" : true }   How can I serialize this object so that all properties that are null don't show up in the JSON string?   In this example, "sopgTemplateName" and all "cardTemplateName" properties are null and should not appear in the JSON string. The empty list "restrictionCountries" should still appear as an empty list, though.