rsync to remote server without password
Why am I still being asked for an ssh password when I'm using private key authentication?
When an object is moving in a circle, won't the frictional force oppose it's motion? And if the velocity is always tangential to the path, there is no component of it towards the center, so there is no component of friction towards the center (since the frictional force is antiparallel). So how can friction be a centripetal force, like in the case of a car rounding a corner? Usually I use the package mhchem for writing chemical formulas, but until now I was not able to find a solution for writing crystals such as Nd^{3+}:YAG properly with this package. When simply writing   \ce{Nd^{3+}:YAG}   it results in an error. My current alternative solution is to write it as   \ce{Nd^{3+}}:\ce{YAG}   Is there a more elegant way to do that? How to take a screenshot of a whole desktop with app menu selection? Add a binary to my path I have an executable. I want to execute the executable in terminal with name only like other commands.  I can put my executable in /usr/local/bin or I could add its PATH to ~/.bashrc. Both will work.  What is better?  Is there  any difference? How to password protect grub menu entry? Is there a way I can password protect grub menu entry- e.g. if I dual boot with Windows 7 can I set it so that a password is needed to boot into Win 7?   Secondly I would also like to protect grub menu entries being changed if possible.  thanks Although Ubuntu 16.04 release notes mention that:  The default VIM package has been built against python3 instead of python2.  Yet after I installed vim with the following command:  sudo apt-get install vim   And checked:  vim --version   It showed:  -python -python3   Is it a bug? How do I get vim with Python support? How to show that $L^p$ spaces are nested? Suppose $1&lt;p_1&lt;p_2&lt;\infty$, then show $L^{p_1}[a,b] \supset L^{p_2}[a,b]$.  I was able to show $\|f\|_{p_1} \le \|f\|_{p_2} (b-a)^{1/p_1 - 1/p_2}$ but I'm not sure how to proceed from here. In a bash shell script, writing a for loop that iterates over string values In bash, I know that it is possible to write a for loop in which some loop control variable i iterates over specified integers.  For example, I can write a bash shell script that prints the integers between 1 and 10: #!/bin/bash  for i in {1..10} do  echo $i done  Is it possible to instead iterate over a loop control variable that is a string, if I provide a list of strings?  For example, suppose that I have a string fname that represents a file name.  I want to call a set of commands for each file name.  For example, I might want to print the contents of fname using a command like this: #!/bin/bash  for fname in {&quot;a.txt&quot;, &quot;b.txt&quot;, &quot;c.txt&quot;} do  echo $fname done  In other words, on the first iteration, fname should have the value fname=&quot;a.txt&quot;, while on the second iteration, fname should have the value fname=&quot;b.txt&quot;, and so on.  Unfortunately, it seems that the above syntax is not quite correct.  I would like to obtain the output:  a.txt b.txt c.txt  but when I try the above code, I obtain this output:  {a.txt, b.txt, c.txt}  Can you please help me determine the correct syntax, so that I can iteratively change the value/contents of the variable fname?  Thank you for your time. I wanna transfer some files from this PC with Ubuntu to a PC with Windows 7 I don't care how to do it (ftp, samba or whatever) I wanna know the steps, I searched a lot but I can't find anything that works. Thank you. I am a graduate student of math right now but I was not able to get a topology subject in my undergrad... I just would like to know if you guys know the best one.. Short story (+radio play?) in which astronauts outside their ship slowly drift apart in space Looking for a short story in which the crew of a spaceship for some reason find themselves outside the ship, drifting apart in outer space. They can communicate via their radios but are individually drifting apart.  One by one, they lose communication as they drift further away from each other.  Might have also been adapted into a radio play? Windows 10 lets you 'schedule' a reboot for later. I want to disable it.  Evidently Windows scheduled itself for a reboot last night when I wasn't looking and just closed everything I had been working on the night before.  I reboot on the regular; I don't need Windows to do that for me.  Can I disable it completely? I don't mind if it downloads everything, and then says "hey, you should reboot," but it should never reboot itself, ever.  I'm using the "Pro" edition of Windows 10. What is likely to happen when you plug two ends of a network cable to a single switch/router? Will this create problems on the network, or just be ignored? Multiple logistic regression power analysis Expected number of hamiltonian paths in a tournament The following theorem is from Alon&amp;Spencer's The probabilistic method, in the beginning of chapter 2:  Theorem 2.1.1: There is a tournament $T$ with $n$ vertices and at least $\frac{n!}{2^{n-1}}$ Hamiltonian paths.  Briefly the theorem is proved by looking at $X_\sigma$ the indicator random variable for a permutation $\sigma$ giving a Hamiltonian path, that is, satisfying $(\sigma(i),\sigma(i+1))\in T$ for $1\leq i \lt n$. Then   $\sum \mathbb{E}\left[X_\sigma\right] = \frac{n!}{2^{n-1}}$.  I don't understand where did this value ($\frac{n!}{2^{n-1}}$) came from! could someone explain it please? What to do if I can't get a visa to attend a conference that accepted my paper? My work got accepted into a very good category in a very good conference in my field. Due to complicated visa issues it will be very hard for me to attend that conference.   If I don't attend the conference they are certainly going to remove my work from the proceedings.  I am worried I won't be able to claim any sort of achievement if I don't attend this conference.  Can I still add it to my CV and specify that my work got accepted in this conference in a very good category? Can't transfer purchases from iPhone to iTunes in iOS 9 After upgrading to iOS 9, I can't transfer purchases from my iPhone to iTunes. It happens to just start the process, then it finishes without transferring anything. However, I can still transfer purchases from my iPad with iOS 8.4 like before.   iPhone 5c, iOS 9 iTunes 12.3 MacBook Pro 13" with Retina Display Mid 2014, OS X El Capitan   Apparently, not many people happen to use this "transfer purchases" feature so it didn't get any real attention. I used it a lot, I used to update my apps on my iPhone, transfer them to iTunes and updated my iPad apps using iTunes. Still, I can update my apps using iTunes and update apps on all my devices. What techniques are available for collapsing (or pooling) many categories to a few, for the purpose of using them as an input (predictor) in a statistical model?    Consider a variable like  (discipline chosen by an undergraduate student). It is unordered and categorical, but it can potentially have dozens of distinct levels. Let's say I want to use major as a predictor in a regression model.  Using these levels as-is for modeling leads to all sorts of issues because there are just so many. A lot of statistical precision would be thrown away to use them, and the results are hard to interpret. We're rarely interested in specific majors -- we're much more likely to be interested in broad categories (subgroups) of majors. But it isn't always clear how to divide up the levels into such higher-level categories, or even how many higher-level categories to use.  For typical data I would be happy to use factor analysis, matrix factorization, or a discrete latent modeling technique. But majors are mutually exclusive categories, so I'm hesitant to exploit their covariance for anything.  Furthermore I don't care about the major categories on their own. I care about producing higher-level categories that are coherent with respect to my regression outcome. In the binary outcome case, that suggests to me something like linear discriminant analysis (LDA) to generate higher-level categories that maximize discriminative performance. But LDA is a limited technique and that feels like dirty data dredging to me. Moreover any continuous solution will be hard to interpret.  Meanwhile something based on covariances, like multiple correspondence analysis (MCA), seems suspect to me in this case because of the inherent dependence among mutually exclusive dummy variables -- they're better suited for studying multiple categorical variables, rather than multiple categories of the same variable.  edit: to be clear, this is about collapsing categories (not selecting them), and the categories are predictors or independent variables. In hindsight, this problem seems like an appropriate time to "regularize 'em all and let God sort 'em out". Glad to see this question is interesting to so many people! When using the xhtml1-transitional.dtd doctype, collecting a credit card number with the following HTML  &lt;input type="text" id="cardNumber" name="cardNumber" autocomplete='off'/&gt;   will flag a warning on the W3C validator:     there is no attribute "autocomplete".   Is there a W3C / standards way to disable browser auto-complete on sensitive fields in a form? What software do you use to accurately draw geometry diagrams?