Can you disable logging in as other users over ssh?
What is the "wheel" user in OS X?
If you draw two cards, what is the probability that the second card is a queen? We had this question arise in class today and I still don't understand the answer given. We were to assume that drawing cards are independent events. We were asked what the probability that the second card drawn is a queen if we take two from the deck. The answer given was 4/52, which seems counter-intuitive to me. How is the probability still 4/52 if there was a card drawn before it? What if the first card drawn was a queen? So a company decides to raise money by selling shares of its stock. The stock is offered at an initial price of their determination. The stock is then traded in a market where forces of supply and demand, as well as speculation, affect its price.  When a company performs well (or makes decisions that will likely increase the company's earnings in the future), more people want to buy that stock than do people wanting to sell it. This creates demand for that stock which causes its sell/bid prices rise. When a company performs poorly, the opposite occurs; more people want to sell the stock than want to buy. This creates a surplus that causes sell/bid prices to fall.  Understanding this, people speculate over company performance to determine the future behavior of a stock, and attempt to "buy low, sell high" or "borrow high, return low" in order to make a profit.  But my question is regarding the first part of that process. What is it about company performance that causes the perceived value of its stock to rise? This is especially perplexing since I would guess that most people don't exercise their voting rights, and many stocks don't pay dividends.  It's not like a shareholder has any direct financial gains from increased company earnings (speculative stock pricing notwithstanding).  What is the intrinsic value of the stock?  It seems to me that all participants in a stock market tacitly agree that stock price will have a direct correlation with company performance. So another way of asking the question is, would an opposite agreement hold? What financially (this isn't a question about logistics, communication, or feasibility) stops all participants in a market from agreeing to value a particular company's stock inversely with respect to the company's performance?  Since I feel like I can't quite nail down my question, another form of it would be, why is stock market behavior driven by company performance? Why does water damage low-voltage microelectronics so easily? Everybody has had the time where water gets all over their electronics, and the whole thing gets ruined, like cell phones.  At that low of a voltage (3-5&nbsp;volts), I don't understand why it is such a short-term harm (long term makes sense - corrosion, etc.)  If an LED was in parallel with water, maybe a bit more current would be drawn, but it doesn't seem to be enough at all to short out the system, and the LED would still shine.  So what is it that permanently damages some electronics and what is the cause? Can you save an image with a white background as a transparent image out of Photoshop? Failed to connect to socket /com/ubuntu/upstart: Connection refused: Errors were encountered while processing: runit Mcrypt extension is missing in 14.04 server for mysql In Ubuntu 18.04.1, I would like to use my left Super-key only to simply open the Show Applications menu (aka Dash) like a left click on the dock-icon (with the 9 dots) does and preferably close it again without showing me any open programs.   I can open it with Super + A and even close it again with Super R, but Super L appears to do nothing at all.   In Xfce, something similar was possible by adding a custom keyboard shortcut for Super L and setting the command to xfce4-popup-whiskermenu, which would open and close a menu with favourite applications. Unfortunately, I don't know the command that opens and closes the Show Applications menu.   Is there any way to add such a shortcut in the new Gnome Shell? Plotting two variables as lines using ggplot2 on the same graph How many times can I repeat a keyword without looking spammy to Google? I have an eCommerce based on Opencart, but I have some doubts about how many times I can repeat the same word.  For example, the keyword is present in the title, description, h1, h2 and is repeated several times in the text:   Page Title: Shop Iphone other keyword Page description: Shop Iphone other keyword   (and they continue appearing below)   H1: Shop Iphone other keyword H2: Shop Iphone other keyword 10 more times in the text: Shop iPhone   I mean, if Googlebot sees the same WORD 30 times, can it be considered SPAM? Can I lose something or can I use keywords a lot?  In WOORANK I saw my review and I noticed that I need to improve my keywords, and a lot. I have some keywords like: payment, description, promotion, sales... keywords really "empty"  [ UPDATE ]  Can repeating keywords make them lose importance? How to distinguish between gold, silver, and bronze tag badges on SEDE? How can I distinguish between the levels of , say , querying ? For example, Mr. Jon Skeet has all the gold, silver and bronze badges for LINQ, so the query select * from Badges b with (nolock) where     b.Name = 'linq' and b.UserId = 22656  returns 3, with no distinction between them. Is it possible to include such information into the dump, for example, keep a unique badge ID (40 for the gold  badge)? How to shut down the computer safely by pressing the power button? So this is pretty simple: when I press the power button whilst the machine is on, it comes up with a menu (of which one of the options is to shutdown)  However, I just want it to just start shutting down once I press the power button without any further interaction!  How do I accomplish this? If $x_1,...,x_n$ are positive real numbers and if $y_k=1/x_k$, prove that $$\left(\sum^n_{k=1}x_k\right)\left(\sum^n_{k=1}y_k\right)\geq n^2.$$   I've been learning induction, and I've come across this problem that I really can't even break down and begin to think about. I've been told it has something to do with Cauchy-Schwarz, but I cannot figure out how to apply it. I would appreciate help figuring out how to go about and formulate this proof. Thanks! options for appearance of links in hyperref If I use  \usepackage[colorlinks]{hyperref}   I get colored links for \cite (not good for printing or even viewing) but table of content looks fine.  If I use  \usepackage[colorlinks=false]{hyperref}   I get \cite  links in black with a colored frame (this looks very good) but the table of content looks strange with extra long boxes.  What are my other options? Can you have two styles in different parts of a document?   How do you make the page numbers in TOC to be the links instead of the section headers? I'm looking for a javascript that can limit the number of lines (by line I mean some text ended by user pressing enter on the keyboard) the user is able to enter in textarea. I've found some solutions but they simply don't work or behave really weird. The best solution would be a jquery plugin that can do the work - something like , but it should be able to limit text line count not character count. Can anyone hint me to prove:  $\forall n\in \mathbb{N}: \exists$ Fibonacci numbers $ F_{i_1},\ldots,F_{i_k}$ such that: $$\sum F_{i_k}=n$$    Note: Every Fibonacci number can appear only once. Thanks Why does the weighing balance restore when tilted and released How to Run an app as Administrator without the prompt? When I start SQL Server Management Studio 2008, I get an error that's been around forever and is documented .  One of the suggestions to fix it that actually worked was to start SSMS with Run as Administrator. So I modified the properties of the shortcut to always run it as the administrator.  The only annoyance is that I get a prompt every single time asking whether I really want to do it. Is there a way to tell just this one program (SSMS) to not pop up the prompt, while keeping this behavior for other apps? Inner Product on $\mathbb{R}$ and on $\mathbb{C}$ This is a question of the book Linear Algebra of Kenneth Hoffman.  Describe explicitly all inner products on $\mathbb{R}$ and on $\mathbb{C}$.  I think that if $&lt;,&gt;$ is one inner product on $\mathbb{R}$ (or $\mathbb{C}$) then $&lt; ,&gt;=K[,]$, where $[,]$ is the standard inner product. Is that correct? I came up some definitions I have sort of difficulty to distinguish. In parentheses are my questions.   $\dfrac {x}{0}$ is Impossible (  If it's impossible it can't have neither infinite solutions or even one. Nevertheless, both $1.$ and $2.$ are divided by zero, but only $2. $ has infinite solutions so as $1.$ has none solution, how and why ?) $\dfrac {0}{0}$ is Undefined and has infinite solutions. (How come one be Undefined and yet has infinite solutions ?) $\dfrac {0}{x}$ and $x \ne 0$, it's okay for me, no problem, but if someone else wants to add something about it, feel free to do it. From time to time I see an enum like the following:  [Flags] public enum Options  {     None    = 0,     Option1 = 1,     Option2 = 2,     Option3 = 4,     Option4 = 8 }   I don't understand what exactly the [Flags] attribute does.  Anyone have a good explanation or example they could post?