In order to install hplip to get my printer working again since the update from Ubuntu 14.04 to 16.04 broke it, I opened a terminal according to the instructions of HP, and during the process I was asked to enter the sudo password, but I cannot enter it; the keyboard is no longer responding to any key. What can I do to continue installing this program?
When I'm about to install a program in the terminal it wants the password:  [sudo] password for xxx:   But when I start to type my password nothing happens. What should I do?
I set up a new VPS instance of Ubuntu and am wondering what the easiest way is to get up and running with a basic LAMP stack (i.e. which packages are required, which configuration options need to be tweaked, if any, etc.). sudo: unable to resolve host   I think I need to edit the /etc/hosts file to make an entry for 127.0.1.1 PC name.  But how can I do that if I can't access sudo? It seems to have gone since I updated to 13.10.  I have tried nano, which still doesn't work. Why is complete strong induction a valid proof method and not need to explicitly proof the base cases? Why don't Death Eaters always use Avada Kedavra? When the Death Eaters attacked Hogwarts, why did the Death Eaters not just use Avada Kedavra and kill everyone? How exactly does Knuth's Up-Arrow notation work? I've done some research, and found this on Wikipedia. \begin{matrix}a\uparrow b=a^{b}=&amp;\underbrace {a\times a\times \dots \times a} \\&amp;b{\mbox{ copies of }}a\end{matrix} \begin{matrix}a\uparrow \uparrow b&amp;={\ ^{b}a}=&amp;\underbrace {a^{a^{{}^{.\,^{.\,^{.\,^{a}}}}}}} &amp;=&amp;\underbrace {a\uparrow (a\uparrow (\dots \uparrow a))} \\&amp;&amp;b{\mbox{ copies of }}a&amp;&amp;b{\mbox{ copies of }}a\end{matrix} I'm still a bit confused on this topic. I've done a lot of research, but I can't seem to understand this. Could somebody explain this in an understandable way? From what I can gather, for example 2↑↑3 would be 2^2^2 = 16? Then 2↑↑↑3 would be 2^2^2^2 = 256? Am I correct, or have I mis-interpreted this? Step in the Stein's proof of Plancherel Theorem apt-get update fails to fetch files, “Temporary failure resolving …” error Err http://archive.canonical.com natty InRelease     Err http://security.ubuntu.com oneiric-security InRelease                Err http://extras.ubuntu.com natty InRelease                             Err http://security.ubuntu.com oneiric-security Release.gpg   Temporary failure resolving ‘security.ubuntu.com’ Err http://archive.canonical.com natty Release.gpg   Temporary failure resolving ‘archive.canonical.com’ Err http://extras.ubuntu.com natty Release.gpg   Temporary failure resolving ‘extras.ubuntu.com’ Err http://gb.archive.ubuntu.com oneiric InRelease Err http://gb.archive.ubuntu.com oneiric-updates InRelease Err http://gb.archive.ubuntu.com natty-backports InRelease Err http://gb.archive.ubuntu.com oneiric Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’ Err http://gb.archive.ubuntu.com oneiric-updates Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’ Err http://gb.archive.ubuntu.com natty-backports Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’  Reading package lists... Done W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric/InRelease       W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric-updates/InRelease   W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/natty-backports/InRelease   W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/InRelease   W: Failed to fetch http://archive.canonical.com/ubuntu/dists/natty/InRelease   W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/InRelease   W: Failed to fetch http://archive.canonical.com/ubuntu/dists/natty/Release.gpg  Temporary failure resolving ‘archive.canonical.com’ W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/Release.gpg  Temporary failure resolving ‘security.ubuntu.com’ W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/Release.gpg  Temporary failure resolving ‘extras.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric-updates/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/natty-backports/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Some index files failed to download. They have been ignored, or old ones used instead.   This is what I'm seeing when I try to run sudo apt-get update. I did an update on my instance yesterday and am now experiencing this. Give an example of a relation R on $A^2$ which is reflexive, symmetric, and not transitive I am just looking for some clarification on this exercise:  Let $A = \{a,b,c,d\}$. Give an example of a relation $R$ on $A^2$ which is reflexive, symmetric, and not transitive.  I understand that if I was only dealing with $A$ and and not $A^2$ I could give an answer similar to:  $R = \{(a,a),(a,b),(a,d),(b,a),(b,b),(c,c),(d,a),(d,d)\}$  Here $R$ is reflexive, symmetric, and not transitive.  What is confusing me is the fact that we have $A^2$. I am not sure what I am missing here. I am looking through my book to see if I can figure this out, but if someone could help shed some light on this it would be appreciated.  Thanks,  Tony How to install (old) packages for Ubuntu 9.04? Based on some excellent feedback by Mark here (), today I was able to use the vmware converter to clone my production server for a staging server.  However the nic won't come up no matter what I do. I attempted to inistall vmware tools, as I suspect that the fact that it is not installed might prevent the nic from working. (I have the nic set as a vmxnet3 card in the vm settings). The install failed because there were several dependencies missing as well as the Linux headers. Given that Ubuntu 9.04 has been EOL'd, the packages I need to install to get the vmware tools to install are no longer available. I doubt the ubuntu 9.04 install CD has the packages on it.   What are my options? I'd rather not upgrade the version of Ubuntu yet, as the point of the vm right now is to maintain parity with the production server. Might I have better luck resetting the driver to use vmxnet2 instead of the vmxnet3?  Thanks in advance!  Chris Should I sign, watermark or otherwise label a framed print? And if so how? How to select JSF components using jQuery? Normally to remove files with spaces in their filename you would have to run:  $ rm "file name"   but if I want to remove multiple files, e.g.:  $ find . -name "*.txt" | xargs rm   This will not delete files with spaces in them. I want to use some constants, height and width, when creating an ellipse but it won't work with \newcommand. Here is a minimal example:  \documentclass[12pt, a4paper]{article}  \usepackage{amsthm, tikz} \usetikzlibrary{arrows, shapes, trees, positioning} \begin{document}  \begin{figure} \centering \begin{tikzpicture}       \newcommand*{\width}{2}%     \newcommand*{\height}{0.5*\width}%      \draw[fill=gray!40] (0, 0) ellipse (\width and \height); \node (Y) at (0,0) {\(Y\)};      \end{tikzpicture} \end{figure}  \end{document}    I get the following error:  error: line 14:  Package PGF Math Error: Unknown operator `a' or `an' (in '2and 0.5*2'). ...ay!40] (0,0) ellipse (\width and \height) command to display time (duration) in human readable form I spent 3 hours trying to write a command to format a time (duration) expressed as a floating number (in seconds) in a nice form as follows:  if the time is &lt; 60 write as a float with 3 decimals (i.e. milliseconds)  else let h,m,s be the hours, minutes and seconds corresponding to the time      if h=0 then write as m:ss (ss always with 2 digits, m can have only 1)      else write h:mm:ss (mm and ss with 2 digits, h can have only 1)   So 1.25678 gives 1.256, 125.35 gives 2:05, 18249 (which equals to 5*3600+4*60+9) gives 5:04:09.  I tried several packages for the comparison/formatting. No success. Can someone help me ? Thanks ! This is a general, community wiki  question to address non-specific "I need a CMS or Wiki that does x, y, and z..." questions.  If your question was closed as a duplicate of this question and you feel that the information provided here does not provide a sufficient answer, please open a discussion on .    I have a list of features that I want for my website's Content Management System (CMS) - where can I find a [free] script that includes all of them? Currently, when someone suggests an edit, they are unable to keep track of it without watching reputation levels or constantly refreshing the page. What I would like is a notification, that shows up like the notification where someone has edited your question, that shows whether a suggested edit has been approved or rejected after the last vote is cast. This way, the community can be notified when their edit has been rejected/approved, while focusing their efforts on another question/answer. Does iTunes Home Sharing transfer in-app purchases? My wife recently got an iPhone and, being that I'm an iPhone user already, I set up iTunes Home Sharing (under my Apple ID) so that I could share some of my purchased apps with her.  While paid apps transferred to her phone without a problem, in-app purchases that I had made under my account didn't transfer over.  Is this the correct behavior? Our phones are set up under different Apple IDs, but I was still able to transfer purchased (paid upfront) apps to her – which is completely allowed under the Terms of Use – so I assumed the same would apply to in-app purchases as well. how to get the current chapter name, section name, subsection name, etc? How can one get the current name of the following: Chapter, Section, Subsection(s), frame, label, mdframed? Given a DateTime object, how do I get an ISO 8601 date in string format? How to set environment variable in systemd service? I have an  and I've created my own service. The configuration service at /etc/systemd/system/myservice.service looks like this:  [Unit] Description=My Daemon  [Service] ExecStart=/bin/myforegroundcmd  [Install] WantedBy=multi-user.target   Now I want to have an environment variable set for the /bin/myforegroundcmd. How do I do that?