Software-Center won't start, can't even reinstall Since today my software-center won' start properly. I tried starting it with software-center from bash but the command cannot be found. I also tried reinstalling the software-center with the terminal sudo apt-get install --reinstall software-center but there is no installation canditate. Also I followed all of the instructions here:  Now the really weird thing is, that I can start it from the sidebar but only if I right-click it and then click on 'Show Details'... then it finally shows up. Any help is appreciated, thanks! Question reframed here since a partial solution was given without solving the core issue:
Software center disappeared [19.10] I have had trouble with sound (now fixed) since upgrading to 19.10, and in the middle of trying the common solutions, the Software Center "disappeared". I got aware of quite late, so I don't know what caused it.  Anyway, would you know how to reinstall it ? Trying sudo apt-get install software-center doesn't work.
Why is there no option to login as root? Why does Ubuntu not allow the GUI users to login as root at the time of system start up like administrator in Windows?  Why they are restricting us to login only through the terminal? $k^{\phi(l)} + l^{\phi(k)} \equiv1\pmod{lk}\,$ if $\,\gcd(l,k)=1$ I would like to prove the following equality: $$k^{\phi(l)} + l^{\phi(k)} \equiv1\pmod{lk}$$if $\gcd(l,k)=1$. What methods can I use? Thank you for your help. Ideal correspondence I'm confusing the ideal correspondence theorem. Is the following  right?  Ideal correspondence: Let $f:A \to B$ be a ring homomorphism. Then there is a one-to-one order-preserving correspondence between ideals of $f(A)$ and ideals of $A$ which contain $\ker(f)$ by $\alpha \mapsto f(\alpha)$ (conversely $\beta \mapsto f^{-1}(\beta)$), and prime ideals correspond to prime ideals, and maximal ideals correspond to maximal ideals. Is it possible to embed a pre-existing DLL into a compiled C# executable (so that you only have one file to distribute)? If it is possible, how would one go about doing it?  Normally, I'm cool with just leaving the DLLs outside and having the setup program handle everything, but there have been a couple of people at work who have asked me this and I honestly don't know. Prove that a closed ball in a metric space is a closed set   My attempt: Suppose $D(x_0, r)$ is a closed ball. We show that $X \setminus D $ is open. In other words, we need to find an open ball contained in $X \setminus D$.   Pick $$t \in X-D \implies d(t,x_0) &gt; r \implies d(t,x_0) - r &gt; 0 $$ Let $B(y, r_1)$ be an open ball, and pick $z \in B(y,r_1)$. Then, we must have $d(y,z) &lt; r_1 $. We need to choose $r_1$ so that $d(z,x_0) &gt; r$. Notice by the triangle inequality  $$ d(x_0,t) \leq d(x_0,z) + d(z,t) \implies d(z,x_0) \geq d(x_0,t) - d(z,t) &gt; d(x_0,t) - r_1.$$  Notice, if we pick $r_1 = d(t,x_0)-r$ then we are done.  Is this correct? How do I disable client side decoration globally in GNOME? I'm using Ubuntu GNOME 17.04. One encounters client side decoration (CSD) as most of the official GNOME applications (Nautilus, gedit, Evince etc.) use  (a combined title bar and toolbar, see linked screenshots) whereas other applications don't. This feature is disabled in Unity, all the applications use traditional separate title bars.  Screenshots (from ):     Nautilus with GtkHeaderBar   Nautilus without GtkHeaderBar     For consistency I want to disable GtkHeaderBars globally (in all the applications using it) and use separate title bars. Is there a way to achieve that?  I have heard of gtk3-nocsd package, but couldn't make it work with GNOME for all the applications. On this  there are more than 50 links to Stack Overflow questions. However, the last 6 links aren't converted to titles (http://facebook.stackoverflow.com/questions/6530420/control-the-image-that-facebook-shows-when-i-like-a-url should be converted to ).   However:  all http://facebook.stackoverflow.com/... into http://stackoverflow.com/... fixes this, both in the preview and the final result. Also, the preview won't show any title for http://facebook.stackoverflow.com/... links.  My question is, what limitations does this converting have? How are these question titles retreived? Via API? Through database?  I'm not sure about title, feel free to edit that I am using a local (company) network which provides some servers which are also available from the outside (through one public static IP and port forwarding). And there are some domains which are pointing to the public IP.  What I want is my domains pointing to the local IPs when being inside the local network. I know I will need a local (internal) DNS server which changes the domains to the IPs. I am able to setup the DHCP server to deliver the DNS to the local clients (so this won't be any problem).  What kind of DNS server software can I use to:   repeat all domains like a DNS would do that but for only my domains use the local values Which configuration of armor enchantments gives maximum protection? Prior to 1.4.6 it was a well known fact that the protection enchantment on armor was strictly superior to the other enchantments and that simply having a few pieces with protection III/IV would max out this protection, leading to the best possible set of armor.  Now that this has , however, I'm curious to see if anyone has analysed what the optimal armor configurations now are?  Presumably it will be some combination of protection enchantments and other enchantments, going by the description of how enchantments work now on the wiki.  Or, are we forced to choose one or more types of protection to max out?  (This would be the case if there are not enough total enchantments possible to max out all areas).  If this is the case, it would be great to see some analysis of how to optimise that choice as well.  I've looked around but haven't found any good mathcrafting on this question yet.  Furthermore, beyond protection against taking damage, can someone include some explanation of the hidden utility bonuses?  For instance, Blast Protection has been described in wiki sources as reducing the knockback effects from explosions, and Fire Protection is described as reducing burn time.  Do these effects scale and max out at some enchantment level, and does Projectile Protection similarly reduce the knockback effect from projectiles? Err http://archive.canonical.com natty InRelease     Err http://security.ubuntu.com oneiric-security InRelease                Err http://extras.ubuntu.com natty InRelease                             Err http://security.ubuntu.com oneiric-security Release.gpg   Temporary failure resolving ‘security.ubuntu.com’ Err http://archive.canonical.com natty Release.gpg   Temporary failure resolving ‘archive.canonical.com’ Err http://extras.ubuntu.com natty Release.gpg   Temporary failure resolving ‘extras.ubuntu.com’ Err http://gb.archive.ubuntu.com oneiric InRelease Err http://gb.archive.ubuntu.com oneiric-updates InRelease Err http://gb.archive.ubuntu.com natty-backports InRelease Err http://gb.archive.ubuntu.com oneiric Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’ Err http://gb.archive.ubuntu.com oneiric-updates Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’ Err http://gb.archive.ubuntu.com natty-backports Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’  Reading package lists... Done W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric/InRelease       W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric-updates/InRelease   W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/natty-backports/InRelease   W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/InRelease   W: Failed to fetch http://archive.canonical.com/ubuntu/dists/natty/InRelease   W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/InRelease   W: Failed to fetch http://archive.canonical.com/ubuntu/dists/natty/Release.gpg  Temporary failure resolving ‘archive.canonical.com’ W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/Release.gpg  Temporary failure resolving ‘security.ubuntu.com’ W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/Release.gpg  Temporary failure resolving ‘extras.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric-updates/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/natty-backports/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Some index files failed to download. They have been ignored, or old ones used instead.   This is what I'm seeing when I try to run sudo apt-get update. I did an update on my instance yesterday and am now experiencing this. I have watched the series of Two and a Half Men two times now till the latest episode, but can't understand why either Charlie or Walden just don't kick Alan out? I mean it is a bit cruel but they are shown to put up with him even though he gets up on their nerves (even got on my nerves).    Some examples off the top of my head:   He became the reason of his first engagement with Mia to be broken up.   He once set up his curtains on fire after ruining his day.   He invited his girlfriend/assistant to move in without his permission and started acting like he owned part of the house when he didn't even pay rent. He acted sickly and dying (Walden's time) and tricked him out of money for his care and comfort.   He deliberately tried to break his relations (Walden's) just so he can keep sponging off.   I know not the best examples, but if not in every episode then in every alternate episode he is shown to getting up on their nerves and they just keep on telling him to leave. Why don't they just kick him out? Why put up with such a leach? Proof by Induction: For any integer $n > 0$, $3|(5^{2n} − 1)$. Hello I am taking a Discrete Mathematics course and having some trouble with this question about sets:  Under what conditions is $A- B = B- A$  Diagram:   Diagram:   Maybe I'm understanding incorrectly, but how can A-B and B-A be equal if they contain elements that are not in each other? If the magnetic field doesn't polarize does it follow the electric field path of propagation? or does it vanish? Why can't I update my Nexus 4 to Lollipop? As I understand it, Android Lollipop (5.0) is now generally available over-the-air. My Nexus 4 briefly offered for an hour or two to install it. I said yes, and watched it start to download. When I next went to unlock my phone, it obviously wasn't installed. Now, when I go into the Settings app, and manually check for updates, it says my phone is up-to-date. It's still on Android 4.4.4.  I don't particularly want to install the developer image, as that'll wipe all the data from my phone. Is there any way I can encourage it to update?  I'm in the UK, if it's relevant. What is the DC of the Tempest Cleric's Wrath of the Storm feature? Using "that" and "this" interchangeably Name of a special matrix I have a matrix which is kind of symmetrical with the other diagonal, i.e., something like  $$A = \left[ \begin{array}{c c c c}    a &amp; b &amp; c &amp; d \\    e &amp; f &amp; g &amp; c \\    h &amp; i &amp; f &amp; b \\    j &amp; h &amp; e &amp; a  \end{array} \right]$$  Does this matrix have a special name in literature? What are it's properties?  And a matrix that is symmetrical by both diagonals   $$A = \left[ \begin{array}{c c c c}    a &amp; b &amp; c &amp; d \\    b &amp; e &amp; f &amp; c \\    c &amp; f &amp; e &amp; b \\    d &amp; c &amp; b &amp; a  \end{array} \right]$$  What's the name of it? Any interesting properties? Command Options on Command Line - Details and Functions? How would you prove that the generating function of $\binom{2n}{n}$ is $\frac{1}{\sqrt{1-4x}}$?  More precisely, prove that( for $|x|&lt;\frac{1}{4}$ ):  $$\sum^{\infty}_{n=0}x^n\binom{2n}{n}=\frac{1}{\sqrt{1-4x}}$$  Background: I was trying to solve $$S=\sum^{\infty}_{n=0}\frac{(2n+1)!}{8^n(n!)^2}=\sum^{\infty}_{n=0}\frac{(2n+1)}{8^n}\binom{2n}{n}$$ Which if we let $f(x)$ be the generating function in question, would be simply $$f(x)+2xf'(x)$$ With $x=\frac{1}{8}$. Is there a simple proof of the first identity?  states it without a proper reference ( states it without proof). Is there an easier way of calculating $S$? (which is $\sqrt{8}$, by the way)