I am trying to install the OpenSSH client on my Ubuntu system since I still receive the following error message:   Reading package lists ... Done Building the dependency tree Reading status information ... Done Openssh-client package is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: 'openssh-client' package has no installation candidate   I checked several forums and thought it was a problem updating my system. So I tried to update and I get this message that some packages can not be installed. I do not know what to do. Here is the answer:                   Err http://sunsite.rediris.es xenial Release.gpg   Can not resolve "sunsite.rediris.es" Err http://sunsite.rediris.es xenial-updates Release.gpg   Can not resolve "sunsite.rediris.es" Err http://sunsite.rediris.es xenial-backports Release.gpg   Can not resolve "sunsite.rediris.es" Err http://sunsite.rediris.es xenial-security Release.gpg   Can not resolve "sunsite.rediris.es" W: Can not retrieve http://sunsite.rediris.es/mirror/ubuntu-archive/dists/xenial/InRelease W: The download of some index files failed, they were skipped, or the old ones were used instead.
I'm trying to install KDE 5 on my Ubuntu 16.04 system as per the instructions in , but I'm getting the below error message when running sudo apt-get install kubuntu-desktop.  Is there something I can do to resolve this?  Need to get 682 kB/326 MB of archives. After this operation, 1,272 MB of additional disk space will be used. Do you want to continue? [Y/n] y Err:1 http://ir.archive.ubuntu.com/ubuntu xenial/universe amd64              gtk2-engines-oxygen amd64 1.4.6-1ubuntu1   Temporary failure resolving 'ir.archive.ubuntu.com' Get:2 http://ir.archive.ubuntu.com/ubuntu xenial/universe amd64              libkf5sendlater5 amd64 4:15.12.3-0ubuntu1 [45.2 kB] Get:3 http://ir.archive.ubuntu.com/ubuntu xenial/universe amd64              libthreadweaver4 amd64 4:4.14.16-0ubuntu3 [46.6 kB] Get:4 http://ir.archive.ubuntu.com/ubuntu xenial/universe amd64              libfarstream-0.2-5 amd64 0.2.7-0ubuntu1 [192 kB] Fetched 284 kB in 1min 9s (4,093 B/s)         E: Failed to fetch http://ir.archive.ubuntu.com/ubuntu/pool/universe/g/             gtk2-engines-oxygen/gtk2-engines-oxygen_1.4.6-1ubuntu1_amd64.deb               Temporary failure resolving 'ir.archive.ubuntu.com'  E: Unable to fetch some archives, maybe run apt-get update or              try with --fix-missing?
How to find the sum of the series $1+\frac{1}{2}+ \frac{1}{3}+\frac{1}{4}+\dots+\frac{1}{n}$? How to find the sum of the following series? $$1 + \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \dots + \frac{1}{n}$$ This is a harmonic progression. So, is the following formula correct? $\frac{(number ~of ~terms)^2}{sum~ of~ all ~the~ denominators}$ $\Rightarrow $ if $\frac{1}{A} + \frac{1}{B} +\frac{1}{C}$ are in H.P. Therefore the sum of the series can be written as : $\Rightarrow \frac{(3)^3}{(A+B+C)}$ Is this correct? Please suggest. I have a Spring MVC web app which uses Spring Security.  I want to know the username of the currently logged in user.  I'm using the code snippet given below .  Is this the accepted way?    I don't like having a call to a static method inside this controller - that defeats the whole purpose of Spring, IMHO.  Is there a way to configure the app to have the current SecurityContext, or current Authentication, injected instead?      @RequestMapping(method = RequestMethod.GET)   public ModelAndView showResults(final HttpServletRequest request...) {     final String currentUser = SecurityContextHolder.getContext().getAuthentication().getName();     ...   } How can I convert a string to boolean in JavaScript? How to mount an internal HDD on start-up? Rails: What's a good way to validate links (URLs)? How do I log into my Linux laptop if I have forgotten both the username and password? Provide two arguments to one option using getopts In below code when I give option r then getopts requires one arguments:  while getopts ":hr::l:" opt; do     case $opt in         r ) echo "Run Numbers - argument = $OPTARG " ;;         l ) echo "Latency range - argument = $OPTARG" ;;         h ) helptext             graceful_exit ;;         * ) usage             clean_up             exit 1     esac done   But I need to pass two arguments after -r option, instead of one. Is there an easy way to do this? How to control your iPad with your Mac remotely? I would like to know, is there a way to control your iPad with your Mac remotely (be able to see and manipulate iPad's desktop on your Mac)? I know that with the TeamViewer or other programs you can control your Mac with your iPad but not vice versa. I'm trying to prove that ${n \choose r}$ is equal to ${{n-1} \choose {r-1}}+{{n-1} \choose r}$ when $1\leq r\leq n$.  I suppose I could use the counting rules in probability, perhaps combination= ${{n} \choose {r}}=\frac{n!}{r!(n-r!)}$.  I want to see an actual proof behind this equation.  Does anyone have any ideas? SPWeb.getFile(Url) exception : value does not fall within the expected range Why can't the end code of an environment contain an argument? Do vulnerability and resistance cancel out? How to remove a watermark from a PDF file? I thought this would be a simple task, but it turned out the other way.  The watermark is the very same (overlapping, but transparent) image on every single page. I created the PDF file myself (so no copyright worries here) using PDFCreator 0.9.8.  I have already tried my friend's Adobe Acrobat Pro, but it didn't work. It tries to remove it, but it can't. I tried to remove header/footer, etc., but the watermark just won't disappear.    How can I remove the watermark? So basically , we all know the direction outside the magnet its from NORTH to SOUTH. but what i don't understand is that what is the direction inside is it the same ?? Book, it follows a guy in a dystopian future Prove the following inequality:   $$\dfrac{e^x + e^{-x}}2 \le e^{\frac{x^2}{2}}$$   This should be solved using Taylor series.  I tried expanding the left to the 5th degree and the right site to the 3rd degree, but it didn't help.  Any tips? If moderators can view , can we see comments we've deleted? We can see our deleted answers, but why not our deleted comments? I understand that the first point release of Ubuntu 18.04, namely 18.04.1 is now available and that my system should now offer it as an update.  My current OS version is 16.04.5 LTS. In System Settings/Software and Updates I have set 'Notify me of a new Ubuntu version' to 'For long term support versions'. I have tried both the main server and the server for United Kingdom, neither offers an update when Software Updater is clicked or via the Ubuntu Software icon.  Can anyone please tell me why I don't get the option of updating to 18.04?  Edit:  I don't remember the details exactly, but I think that my last LTS point release update was offered automatically a lot sooner after the published release date than where we are now with 18.04.1.  Edit 10th August  It appears that there has been some problem with the update process and that it should be fixed next week, see:    Edit 14th August 18.04.1 LTS now available from UK server, How to use Redstone dust in Minecraft PE? I have Minecraft Pocket Edition and I have collected a lot of redstone dust. For some reason, I couldn't use it for things such as iron doors. Why? Hide Accesibility icon from Panel I have Ubuntu 18.04 and set the Scaling Factor in Tweaks to 1,10 because the 1920x1080 resolution makes stuff on my screen look a bit too small for my taste. That toggled this stickman icon, which now seems to not want to go away from my Panel unless I disable "Large Text".    Is there any way to hide this icon while keeping my settings?