I installed openssh-server,it will start ssh server on boot automatic.But I don't want that.How to forbid ssh server to autostart on boot?
I read about how to enable and disable services in Ubuntu and it seems that there are different possibilities to manage them.  The first method I found is update-rc.d to add new services to startup, which aims on the /etc/init.d folder and its contents.  The other one I found is to edit .conf files in the /etc/init folder.  What's the recommended way to enable / disable / add services and why?  Could you please give a short bulletproof step by step example on how to add a service in Ubuntu and enable and disable it?
Rendered image looks pixelated When I hit F12 to render an image and zoom in it is quickly pixelated. How can I render a higher res display? I have looked through the settings and couldn't find a solution. Show that the set of all polynomials whose constant term is a multiple of 3 is an ideal of the ring $Z[x]$.   Attempt: Suppose then we need to show   if $p(x), q(x) \in I$ then $p(x) + q(x) \in I$  and if $r(x) \in Z[x]$ , then $p(x)r(x) \in I$ and $r(x)p(x) \in I$.  And $0 \in Z$, then $0 \in I$.  Then let   $I =$ {$a_nx^n + a_{n-1}x^{n-1} + ...+a_1x + a_0$ | $a_i \in Z$, $a_0\in 3Z$}  $p(x)  = a_nx^n + a_{n-1}x^{n-1} + ...+a_1x + 3a$  and $q(x) = b_mx^n + b_{m-1}x^{n-1} + ...+b_1x + 3b$  Here we do not assume that $p(x) $ and $q(x)$ have the same degree.  Then $p(x) + q(x)  = [a_nx^n + a_{n-1}x^{n-1} + ...+a_1x + 3a]  +  [b_mx^n + b_{m-1}x^{n-1} + ...+b_1x + 3b] = 3(a + b) + (a_1 + b_1)x + ....+ (a_n + b_m)x^n$.  so $p(x) + q(x) \in I$  And $0 \in Z$ is also in $I$, since for $p(x) = 0x^n + ....+ 3(0) = 0$.  And let $r(x)= c_nx^n + ...+3c  \in Z[x] $.  Then $r(x)p(x) = 3(3ac) + (3b_1 + 3a_1) + ....+ a_nb_mx^{2n}$  So $r(x)p(x) \in I$.  Can someone please help? I am not really sure how to prove this. I am getting confused with the underscrips Any help or better approach would really help. Thanks in advance! rstrip not removing newline char what am I doing wrong? What are the options for managing multiple Ubuntu installations together and keeping them in same state When I open this ssh tunnel:  ssh -nXNT -p 22 localhost -L 0.0.0.0:8984:remote:8983   I get this error when trying to access the HTTP server running on localhost:8984:  channel 1: open failed: administratively prohibited: open failed   What does this error mean, and on which machine can you fix the problem? Im having a bit of trouble drawing a circuit with a diode in. I know the current flows from negative to positive, but convention says that current goes from positive to negative.  When drawing a circuit with a diode do you draw the arrow pointing to the positive (matching the actual flow of electrons) or towards the negative terminal (matching conventional current)?  If you follow convention then surely when building circuits from the diagram the diode will not allow current as it is actually facing the incorrect way? My friend and I are planning a vacation to Ireland later this year. We'll be there for a week, flying into Dublin and then renting a car and driving around the country.  Both of us are 23. Are there any age restrictions on renting cars in Ireland? What would be the cheapest/best option for us? If $X$ and $Y$ are independent $N(0,\sigma^2)$, then $X^2+Y^2$ and $X/Y$ are independent? If $X$ and $Y$ are independent, then $X^2+Y^2$ and $X/Y$ are independent? I was solving the problem for the case that $X$ and $Y$ are independent $N(0,\sigma^2)$.  So i found that $X^2+Y^2$ is negative exponential, $X/Y$ is Cauchy distribution. How can i prove that $X^2+Y^2$ and $X/Y$ are independent?  Also, what it will be if the case for general random variable $X$, $Y$ with  $X^2+Y^2$ and $X/Y$ are defined? Proving a sequence defined by a recurrence relation converges How can I prove that this iterative sequence converges to $2$? Can I use the convergence definition?  $$a_{n+1} = \frac{a_n}{2} + \frac{2}{a_n},\qquad  a_0 = 4  $$  Thanks for the help. Yield return from a try/catch block Movie/TV series with a scene of spiky, black goo growing out of a lab container? There was a scene from a sci-fi horror video, not animated, don't know if it's a movie or TV series, where there was this black goo in a glass container and some scientists were looking at it under a microscope.   The pitch black goo grew and grew so fast, eventually breaking out of the inner box and the scientists that were inside the "inner lab" were begging to get out but the scientists outside that inner lab refused to open the door. The black goo was spiky (had spikes).  It's not any of the "Alien" movies, "The Blob", "Life", or "The Thing". It's not vintage. It was made after 1990, I'm pretty sure. Can I boil milk unattended (and still keep the pan clean)? Why doesn't Ubuntu ship an application, or the latest versions of some applications? What reasons are there for applications in Ubuntu not being the most up-to-date, and why are some applications not available, in its  repositories? Big-O Notation Proof Given the definition of Big-O, prove that $f(n) = n^2 - n$ is $O(n^2)$.  When I use the given definition, I get $n^2 - n \leq n^2 - n^2$ which means that $n^2 -n \leq 0$, which is not true. Is there some step I'm missing? Can I charge my laptop with a charger that has different specifications? "Pandora's Box" metaphors The majority of definitions give the same meaning - "Pandora's box" is a synonym for "a source of extensive but unforeseen troubles or problems."  Are there any other metaphors with the same meaning? In what order should the Star Wars movies be watched? Please don't lynch me, but I've never sat through an entire Star Wars film. I'm aware that the 3 (new) films are technically prequels, but I feel strange watching 3 new films then 3 old films?  Do I need to watch the new ones then the old ones? My processor is an Intel Core 2 Duo P8600 (2.40GHz). As far as I know that's a 64-bit processor - I'm a bit confused as the architecture is called AMD 64, is this a generic name given to 64-bit architectures? I've heard of x64 but can't see a release labelled with this. Need to prove that $(S,\cdot)$ defined by the binary operation $a\cdot b = a+b+ab$ is an abelian group on $S = \Bbb R \setminus \{-1\}$. Why am I getting "size mismatch" errors from the Iceland mirror? After installing Ubuntu 12.04 (clean install) I fetch a bunch of program via synaptic (installed specially), all programs worked except Gimp 2.8. So I tried purging Gimp, install again (no luck). Checked broken packages and reinstalled them. When using the Software center I get this MSG:  Failed to fetch http://is.archive.ubuntu.com/ubuntu/pool/main/o/openexr/libopenexr6_1.6.1-4.1_amd64.deb Size mismatch   Tried also this:  sudo apt-get purge gimp* sudo add-apt-repository ppa:otto-kesselgulasch/gimp sudo apt-get update sudo apt-get install gimp   And get this MSG:  Failed to fetch http://is.archive.ubuntu.com/ubuntu/pool/main/o/openexr/libopenexr6_1.6.1-4.1_amd64.deb  Size mismatch E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?   I am wondering if the Icelandic Archive has an outdated version or something?   would really like to install Gimp 2.8 but Gimp 2.6 is OK to.   I am also wondering if I am doing something wrong?