I was searching for a way to disable sudo password promot , then I found a command to remove the user password sudo passwd -d username but after I wrote it and try to make sudo commands it asks for the password, i tried to put the old password and blank password but unfortunately it says  Sorry, try again  What should I type or do ?
I have a realy strange problem in Ubuntu 11.10. I have by accident my password set to empty. If I wan't to install software now the system asks for a password, but I haven't one anymore. If I enter my old password it sais it's wrong and if I leave it empty it also does. Now I wan't to set my password back, but the system asks for the old password before I can change it. That password doesn't exist, so I can't do anything anymore! Can someone help me please?
What are the differences between a pointer variable and a reference variable in C++? I know references are syntactic sugar, so code is easier to read and write. But what is the difference between a pointer variable and a reference variable? Why do rainbows have distinct colors? When I searched on the Internet for the reason of formation of , I got many explanations like  one &amp; . All the explanations consider only one spherical water droplet (like ).  Why don't the refracted waves coming from the adjacent droplets interfere with each other? For example, why doesn't a red ray coincide with a violet ray coming from another droplet at a suitable position?   How are we able to see rainbows with distinct colors? Since there are thousands of raindrops in the sky when it is raining, shouldn't it be a mess due to overlapping of different wavelengths?  Please explain. Using "recently" with past simple Is it fine to use recently with the past simple tense in the following sentence?     Did you read any books recently?   Is it grammatically correct?  Or do I have to use:     Have you read any books recently? How to transpose a dataset in a csv file? I have the following problem: I correctly obtain a numbered bibliography at the end but along the text the cite_key appear instead of a number. How to fix this problem?   \documentclass[11pt]{book}  \usepackage[]{biblatex} \begin{document} %some text  ... \cite{ABKM2015}... %some text  \begin{thebibliography}{99} \bibitem{ABKM2015} Arroja, F. and Bartolo, N. and Karmakar P. and Matarrese, S. (2015). \newblock The Two Faces of Mimetic Horndeski Gravity             \newblock {\em ArXiV}, 1506.08575 (2015). \end{thebibliography} \end{document}   After compiling I get ... [ABKM2015] ... while I want for example  [1]. How do we know the universe is expanding, and not that its contents are shrinking? Is there a physical reason why not to think that instead of space expanding, all physical constants and parameters are shrinking (including of course the instruments we use to measure the constants) and space is static, or is it a case of Occam's razor? Regular expression to match non-ASCII characters? What is the easiest way to match non-ASCII characters in a regex? I would like to match all words individually in an input string, but the language may not be English, so I will need to match things like ü, ö, ß, and ñ. Also, this is in Javascript/jQuery, so any solution will need to apply to that. Drush from GitHub stopped working I have a  that has been working since it moved there.  I did a git pull this morning, and am now getting errors:     $ drush      Warning: require(/home/mpd/drush/vendor/autoload.php): failed to open   stream: No such file or directory in   /home/mpd/drush/includes/bootstrap.inc on line 1007      Fatal error: require(): Failed opening required   '/home/mpd/drush/vendor/autoload.php' (include_path='.:') in   /home/mpd/drush/includes/bootstrap.inc on line 1007   How can I fix this? I have a dataset with a large number of Yes/No responses. Can I use principal components (PCA) or any other data reduction analyses (such as factor analysis) for this type of data? Please advise how I go about doing this using SPSS. Applying for tourist visa for US in country other than your own Possible Duplicate:          Can British passport holders apply for a B2 USA visa from other countries, if they are living there? Or do they have to go back to Britain to apply for it? How do I troubleshoot high 'svchost.exe' usage in Windows 7? How to convert hex string to float in Java? SOQL: Comparing two custom relationship fields in a nested query What is bracketing? I have seen this term a lot and I was wondering what, in basic terms, what bracketing/autobracketing is.  Also, why would one want to 'bracket'?  P.S. - there are other questions asking what DoF and WB bracketing is but none asking quite the same as this. Is a hash a zero-knowledge proof? I’m trying to wrap my head around zero knowledge proofs, but I’m having trouble understanding it.  In my current understanding, zero-knowledge proofs prove to the recipient that the sender has a certain knowledge without disclosing it. Like trying to say your password without actually giving it.  Many sources go at it with a convoluted method like a tunnel where there’s a hidden gate, and Bob is trying to know if Alice can go through the hidden gate. But then it starts saying that Bob should not see Alice enter. Wouldn’t it be easier for Bob to just see Alice go in one tunnel and come out the other? That would not disclose the secret way of opening the tunnel, right?  In that line of thinking, given a one-way function like a hash, couldn’t the other person just hash their secret and let the other see that the hashes compare?  I must be missing something (as there’s a lot of research going into it and hashes are well-known), but I can’t wrap my head around it.  Can someone tell me what’s wrong with my understanding of zero knowledge proofs? I'm used to creating Java Edition Minecraft maps, where NBT can be used to set many different block, item, and entity properties, like an item's CanPlaceOn/CanDestroy list, a chest's items, and more! To open my maps up to more players, I've started creating maps on Minecraft Bedrock Edition as well. But NBT is inaccessible from commands in BE, which I knew before, but didn't know how much of a problem I would have creating these complicated command chains. One of the things that I've always been doing is giving players items with custom item names, lores, enchantments, and other properties. But there is a problem. All this would have been done in NBT in Java Edition. In Bedrock, NBT is inaccessible from commands, meaning the commands I used in JE don't work. Are my dreams crushed? What's the best way to do a backwards loop in C/C#/C++? I need to move backwards through an array, so I have code like this:  for (int i = myArray.Length - 1; i &gt;= 0; i--) {     // Do something     myArray[i] = 42; }   Is there a better way of doing this?  Update: I was hoping that maybe C# had some built-in mechanism for this like:  foreachbackwards (int i in myArray) {     // so easy }   Update 2: There are better ways. Rune takes the prize with:  for (int i = myArray.Length; i-- &gt; 0; ) {         //do something } //or for (int i = myArray.Length; i --&gt; 0; ) {     // do something }   which looks even better in regular C (thanks to Twotymz):  for (int i = lengthOfArray; i--; ) {         //do something } Why separate Stack Exchange accounts? I understand the reason why Stack Exchange has different sites to separate  from  or . I understand too why the reputation is associated on each site.   Why do I have to create a new  for each web site? I know that when I create a new account, it is automatically associated to my other accounts. But, is there a reason why, when I originally create a user on the first site, I can't go on another site with this user? I noticed a peculiar behavior of my Ubuntu 13.04 (although possibly it's also present in previous versions): when my system freezes completely (I do not ask for troubleshooting this) so that even X does not respond to Ctrl+Alt+FX keys, the CapsLock toggle diode on my keyboard blinks (with frequency of ~1Hz), although the system is completely unresponsive.   What is the cause of this phenomena? Is it caused by some internal kernel mechanisms? Is this specific to Ubuntu (is it caused some custom Ubuntu additional software)? Does it has anything to do with HAL? What is the purpose of it? Can I customize this behavior on Ubuntu? How to encrypt folders (not in Home)?