I changed the SSH port on my server, but I then forgot to open a hole in the firewall for that port specifically. Now I cannot SSH into my server anymore. Is there any way around this?  Thanks
Let's say it again, we all make mistakes, and I have just made one.  A brief history: I was doing some stuff on a VPS (Debian) I'm renting, when I noticed some strange behaviour. Using the netstat command I saw an non-authorized connection through SSH. I didn't know what to do, so I decided to close his connection using iptables:  iptables -A INPUT -p tcp --dport ssh -s IP -j DROP   But I am tired, and I wrote  iptables -A INPUT -p tcp --dport ssh -j DROP   and I kicked myself (and everyone else) out...  How do I fix this?
Is it OK to ask on SO for help in explaining someone else's working piece of code, from Open Source projects or library examples etc.? Or does this belong somewhere else? Prove that $\sqrt{n} \le \sum_{k=1}^n \frac{1}{\sqrt{k}} \le 2 \sqrt{n} - 1$ is true for $n \in \mathbb{N}^{\ge 1}$ Display Custom Fields in a SharePoint 2010 Content Query Web Part Using SharePoint 2010, Having Custom List With 4 Columns, Now I am Using Content Query Web-part To Display List Data ,But Currently It Display Only First Column, SO How to Display Custom Fields in a SharePoint 2010 Content By Query Web Part DML is not allowed in a constructor. Is there a known reason behind this limit?  I have been searching for the answer &amp; haven't found anything which addresses the question. May be it's not documented anywhere(Or google doesn't know where it is). Gray cone obscuring/clipping the 3D Viewport Studying the equation $\ln(x)- 1+ x^2=0$ Yesterday, I've listened to a song called "Fear not this night". I find the syntax unusual (as a foreigner, I have never encountered it). Is it the same meaning as "Don't fear this night" ? What's the slight difference between these 2 ?  Thank you for your time. Fantasy piece involving different worlds and a crippled protagonist This is a novel that I think I remember reading somewhere in the 1990s courtesy of my brother (who does not remember the book). Only a few details are coming to mind at the moment. It's a male protagonist. Something was not quite right with his legs, which led to him being nicknamed Frog or Leapfrog due to his usual method of locomotion, which consisted of pushing off from his legs to his hands and vice versa. Something happens and he winds up moving between a number of worlds (I want to say that he fell into a well or a hole in a field). There was a part which stuck with me where he's in a bottomless hole and finds he keeps falling faster and faster without end with the rushing wind becoming actively painful (I don't remember if he actually reaches a terminal velocity or if some aspect of the world prevented it while still allowing the rushing air to affect him physically).  Unfortunately, that's all I can remember. I don't remember whether he eventually gains companions on the voyage or how it ended. The most vivid memory is that of the nonstop falling. Is $f(x,y) = |xy|$ differentiable in $(0,0)$? I have no idea how to approach this problem. Odds of rolling doubles or triples given N 6-sided dice Over the holidays I played a dice game where each player had 3 to 7 d6 to roll each turn.  The game gave certain advantages to doubles and triples.  I wanted to know the odds of rolling doubles or triples given N dice to understand the importance of "upgrading" to more dice.  My question is really about how to reason about such problems:  It's easy to see that the odds of rolling doubles with 2 d6 are 1/6 (first die can be anything, and 1/6 of the time the second will match).  It's also easy to see that with 7 dice the odds are 1.0 (6 dice could be 1..6, but the 7th must match one of them).  The middle cases are fuzzier to me.  I ended up writing a program to enumerate all of the possibilities (even 6^7 is only 279,936 cases to evaluate) because that was the only way I felt I could verify any closed formula I came up with.  This also enabled me to distinguish cases of multiple doubles (or triples).  I would like to know how to derive closed forms and how to validate such solutions without brute-force simulation. How to calculate a heading on the earths surface? Given an initial position and a subsequent position, each given by latitude and longitude in the WGS-84 system.  How do you determine the heading in degrees clockwise from true north of movement? I've heard that exposing database IDs (in URLs, for example) is a security risk, but I'm having trouble understanding why.  Any opinions or links on why it's a risk, or why it isn't?  EDIT: of course the access is scoped, e.g. if you can't see resource foo?id=123 you'll get an error page. Otherwise the URL itself should be secret.  EDIT: if the URL is secret, it will probably contain a generated token that has a limited lifetime, e.g. valid for 1 hour and can only be used once.  EDIT (months later): my current preferred practice for this is to use UUIDS for IDs and expose them. If I'm using sequential numbers (usually for performance on some DBs) as IDs I like generating a UUID token for each entry as an alternate key, and expose that. Say I had  and I used  on something, could I respond to Cloudshift bringing the creature back into play with  or something similar? Knots in Smoothing Splines In , there's this line under the section describing Smoothing Spline's tuning parameter $\lambda$:       In fitting a smoothing spline, we do not need to select the number or   location of knots - there will be a knot at each training observation,   $x_1,...,x_n$.   But, in my opinion wouldn't that be overfitting?     Reason for such a claim: If there are more points which act as knots in the Spline fit, then the range for each slot for fitting is very small. Thus each change in the data, is recognized and imititated in the fit. Thus fitting the changes, which are random, and do not mean anything. Thus overfitting.    Possibilities: We know that cubic splines and Smoothing splines are different. The basic differences are:     Smoothing splines try to minimize the function $$\sum_{i=1}^n(y_i-g(x_i))^2+\lambda\int g''(t)^2dt$$ Smoothing splines shrink the parameters.   Moreover, Smoothing Splines are basically natural cubic splines, and thus they're smooth too.  So, how can these differences( and properties) save the Smoothing Spline from overfitting? Is there anything else that I'm missing here? Does Moore's law apply to quantum computing? Plain and simple. Does  apply to quantum computing, or is it similar but with the numbers adjusted (ex. triples every 2 years). Also, if Moore's law doesn't apply, why do qubits change it? How to connect nodes to node group inputs and outputs in python? Can we get by as English speakers visiting Iceland? We're going to Iceland for the first time in September. Will we be able to get around ok just speaking English, or should we try to learn some rudimentary Icelandic? And is that even what their language is called? Proving that: $\lim\limits_{n\to\infty} \left(\frac{a^{\frac{1}{n}}+b^{\frac{1}{n}}}{2}\right)^n =\sqrt{ab}$ Let $a$ and $b$ be positive reals. Show that $$\lim\limits_{n\to\infty} \left(\frac{a^{\frac{1}{n}}+b^{\frac{1}{n}}}{2}\right)^n =\sqrt{ab}$$ Trig integral $\int ( \cos{x} + \sin{x}\cos{x}) \, dx $ Assume we have:  $$ \int (\cos{x} + \sin{x}\cos{x}) \, dx$$  Two ways to do it:  Use $$\sin{x}\cos{x} = \frac{ \sin{2x} }{2} $$ Then $$ \int \left(\cos{x} + \frac{\sin{2x}}{2} \right) \, dx = \sin{x} - \frac{ \cos{2x} }{ 4 } + C. $$ The other way, just see that $ u = \sin(x), du = \cos(x)dx $, $$ \int ( \cos{x} + \sin{x}\cos{x}) \, dx = \sin{x} + \frac{\sin^2{x}}{2} + C. $$  Now the part I don't see fully is, why aren't these results completely equal?  Taking the 2nd result, \begin{align} \sin{x} + \frac{\sin^2{x}}{2} &amp;= \sin{x} + \frac{1}{2} \, \left( \frac{1 - \cos{2x}}{2} \right) \\ &amp;= \sin{x} + \frac{1}{4} - \frac{\cos{2x}}{4}. \end{align}  So you have to absorb $\frac{1}{4}$ into $C$ for them to be equal.  Shouldn't they be equal straight away? I just created my new character 2 hours ago and I've reached a town. Sometimes random guards will comment that I look ill, or that I should rest. "You look sick, honey. Do you want to lie down?", isn't uncommon.  Did I unexpectedly get vampirism? I didn't fight any vampires, only a couple of wolves and bandits.  I'm a dark elf, so maybe my race isn't seen much around Skyrim and the remarks are more roleplay than actual illness.  Any ideas?