tried: sudo apt-get install git-hg doesn't work.
Simple enough question: is there some shell command (or GUI method) I can use that, given the path to a file on my system, tells me what package put it there? Assuming the file did in fact come from a package, that is.  Bonus question: what if it's a file that isn't installed on my system? Is there, say, a website that will let me look up a file and see what packages, if any, provide it?
Take any three random variables $X_1$, $X_2$, and $X_3$.   Is it possible for $X_1$ and $X_2$ to be dependent, $X_2$ and $X_3$ to be dependent, but $X_1$ and $X_3$ to be independent?  Is it possible for $X_1$ and $X_2$ to be independent, $X_2$ and $X_3$ to be independent, but $X_1$ and $X_3$ to be dependent? Accessing static member through invalid pointer: guaranteed to "work"? Why can we distinguish different pitches in a chord but not different hues of light? In music, when two or more pitches are played together at the same time, they form a chord. If each pitch has a corresponding wave frequency (a pure, or fundamental, tone), the pitches played together make a , which is obtained by simple addition. This wave is no longer a pure sinusoidal wave.  For example, when you play a low note and a high note on a piano, the resulting sound has a wave that is the mathematical sum of the waves of each note. The same is true for light: when you shine a 500nm wavelength (green light) and a 700nm wavelength (red light) at the same spot on a white surface, the reflection will be a superposition waveform that is the sum of green and red.  My question is about our perception of these combinations. When we hear a chord on a piano, we’re able to discern the pitches that comprise that chord. We’re able to “pick out” that there are two (or three, etc) notes in the chord, and some of us who are musically inclined are even able to sing back each note, and even name it. It could be said that we’re able to decompose a Fourier Series of sound.  But it seems we cannot do this with light. When you shine green and red light together, the reflection appears to be yellow, a “pure hue” of 600nm, rather than an overlay of red and green. We can’t “pick out” the individual colors that were combined. Why is this?  Why can’t we see two hues of light in the same way we’re able to hear two pitches of sound? Is this a characteristic of human psychology? Animal physiology? Or is this due to a fundamental characteristic of electromagnetism? How to create a new figure in MATLAB? I have 12.10 ubuntu and when I try to remove / install programs I get notification :      Software can't be installed or removed because the authentication service is not available.    (org.freedesktop.PolicyKit.Error.Failed: ('system-bus-name', {'name':  ':1.104'}): org.debian.apt.install-or-remove-packages   When I log in as root user (instead of user account that I regulary use) i have no problems. Can you say "are not we all?" instead of "aren't we all?" Because "aren't" translates to "are not" I pose the question, can you use both interchangeably (in the context of "aren't we all?")? "Are not" sounds very grammatically incorrect in this situation. Can you say "you need not go there" as opposed to "you needn't go there"?   Basically, I thought you can say "you need not" instead of "you needn't" but that you can't say "are not" instead of "aren't" (in the context I've provided) because I've never heard the second.  My friend believes that if you can use one example interchangeably, you can use the other as well.  So,   Can you use example '1' interchangeably? Can you use example '2' interchangeably? When I try to start Runescape I get an error message that says: CLassNotFoundException and lists Rs2Applet.class. How do I fix this so I can play? What is Reflection in Java Can anyone explain? Modifying list while iterating Which is correct: "has died" or "died"? To me, using Present Perfect form means the event can occur again. So, saying      someone has died   may not be grammatically correct.  Also, I noticed (it might be just coincidence):     passed away   is used more often than     has passed away   Is using Present Perfect correct here? How do you measure pedal axle/spindle size?  Replacement pedals and accessories specify a size like 9/16" or 1/2".  How do I measure my current pedal to see what I need?  Is it just a matter of putting the pedal threads in a caliper and measuring the outer diameter of the threads across the axle/spindle?  Or do you need to measure the solid part, excluding the threads? I run sudo apt-get install git-all in Ubuntu 16.04 and see the following in the end  Setting up runit (2.1.2-3ubuntu1) ... start: Unable to connect to Upstart: Failed to connect to socket /com/ubuntu/upstart: Connection refused dpkg: error processing package runit (--configure):  subprocess installed post-installation script returned error exit status 1 dpkg: dependency problems prevent configuration of git-daemon-run:  git-daemon-run depends on runit; however:   Package runit is not configured yet.  dpkg: error processing package git-daemon-run (--configure):  dependency problems - leaving unconfigured No apport report written because the error message indicates its a followup error from a previous failure.                       Errors were encountered while processing:  runit  git-daemon-run E: Sub-process /usr/bin/dpkg returned an error code (1)   I get the error after rebooting my system also. It really blocks my whole system.  I run killall update-notifier. I run sudo apt-get install git-all but  I get the same error message. I run pgrep -a apt but get nothing as output. I run pgrep -a update but get nothing as output.  A bug report about the case .    In Grub, Choose Advanced options > Ubuntu (Upstart) Linux kernel 4.22. Doing the same only in terminal without systemd causes the same error.      Why is this error here with runit? I know how to compute modular multiplicative inverses for co-prime variables $a$ and $b$, but is there an efficient method for computing variable $x$ where $x &lt; b$ and $a$ and $b$ are not co-prime, given variables $a$, $b$ and $c$, as described by the equation below?   $ a x \equiv c \mod b $   For example, given  $ 154x \equiv 14 \mod 182 $, is there an efficient method for computing all the possibilities of $x$, without pure bruteforce?  Please note that I'm not necessarily asking for a direct solution, just a more optimized one.    I do not believe that the Extended Euclidean Algorithm will work here, because $a$ and $b$ are not co-prime.   Edit:  Follow up question, since the first one had a shortcut:  Could the be computed efficiently as well?  $12260x \equiv 24560 \mod 24755$.  $107$ needs to be one of the computed answers. How can I repair grub? (How to get Ubuntu back after installing Windows?) Remove blank attributes from an Object in Javascript How do I remove all attributes which are undefined or null in a JavaScript object?  (Question is similar to  for Arrays) It's supposed to be zero but for some reason the result produces a peculiar series of digits at the end.  Also, here's the .xlsx of it: http://83.212.111.36/Book1.xlsx Let $x_1,x_2,\ldots,x_n$ be the roots for $1+x+x^2+\ldots+x^n=0$. Find the value of   $$P(1)=\frac{1}{x_1-1}+\frac{1}{x_2-1}+\ldots+\frac{1}{x_n-1}$$   Source: IME entrance exam (Military Institute of Engineering, Brazil), date not provided (possibly from the 1950s)  My attempt: Developing expression $P(1)$, replacing the 1 by $x$, follows $$P(x)=\frac{(x_2-x)\cdots (x_n-x)+\ldots+(x_1-x)\cdots (x_{n-1}-x)}{(x_1-x)(x_2-x)\cdots (x_n-x)}$$    As $x_1,x_2,\ldots,x_n$ are the roots, it must be true that   $$Q(x)=(x-x_1)\cdots(x-x_n)=1+x+x^2+\ldots+x^n$$ and  $$Q(1)=(1-x_1)\cdots(1-x_n)=n+1$$ Therefore the denominator of $P(1)$ is  $$(-1)^{n} (n+1).$$ But I could not find a way to simplify the numerator.  Another fact that is probably useful is that  $$1+x^{n+1}=(1-x)(x^n+x^{n-1}+\ldots+x+1)$$ with roots that are 1 in addition of the given roots $x_1,x_2,\ldots,x_n$ for the original equation, that is  $$x_k=\text{cis}(\frac{2k\pi}{n+1}),\ \ k=1,\ldots,n.$$  This is as far as I could go...    Hints and full answers are welcomed. How do I delete unique rows from a table with duplicate keys? I have the following data:        road        |  ID  | other column  | other column |  ------------------+------+---------------+--------------+           MAIN ST           |  1   |     ...       |     ...      | MAIN ST           |  2   |     ...       |     ...      |         MAIN ST           |  3   |     ...       |     ...      | BERRY LN          |  4   |     ...       |     ...      | BERRY LN          |  5   |     ...       |     ...      | BERRY LN          |  6   |     ...       |     ...      | JOHN RD           |  7   |     ...       |     ...      | JOHN RD           |  8   |     ...       |     ...      |   I want all rows with duplicates in the road column removed. It does not matter to me which duplicates are removed. The end result can look something like this:        road        |  ID  | other column  | other column |  ------------------+------+---------------+--------------+           MAIN ST           |  3   |     ...       |     ...      | BERRY LN          |  4   |     ...       |     ...      | JOHN RD           |  8   |     ...       |     ...      |   where the id's are any value, as long as the road column is unique.   Is there a simple way to do this in SQL or T/SQL? I followed the guide , but it only applies to duplicate keys with non-unique rows. Register On-Click Event with jQuery - Not Firing Why no ooVoo on ubuntu? The only reason I ever boot into Windows (7) is to use the popular video chat software ooVoo (). It's useless under Wine and there seems to be no way to run it in Ubuntu except for some proprietary tools. Does anyone have any information on some alternatives to running it with Wine?