I've installed gnome desktop and now I don't have unity desktop.  How can I reinstall it?
I wanted to try gnome-shell in 11.10 (also 12.04 now)  I removed it, however, classic Gnome is still there and the battery icon is changed (too big and can't use a icon pack on it like faenza)   Also, numerous applications were added and the entries remain on the login screen.    How can I remove it completely, rolling back all changes made when installing gnome-shell?
Proof of property of abelian group I want to show that $\forall x$,$y\in G$, $(xy)^2=x^2y^2 \iff G $ is an abelian group.  Proof of the backward direction seems easy enough:  Assume $G$ is an abelian group. Then consider $(xy)^2=(xy)(xy)$. By associativity, $(xy)(xy)=xyxy$. Since $G$ is abelian, $xyxy=xxyy=x^2y^2$.   Proof of the forward direction I attempt by contrapositive:  That is, assume $G$ is not an abelian group. Then, consider $(xy)^2=xyxy$ as above. Yet, $xyxy\neq xxyy=x^2y^2$ since we no longer have commutativity.  Is this proof by contrapositive completely correct? How to compile .c file with OpenSSL includes? Continuity of a convex function I'm trying to solve the following problem:  Let $f:K\rightarrow \mathbb{R} $, $f$ convex and $K \subseteq \mathbb{R}^n$ convex. Then $f$ is continuous on $K$.   I have proved the only case $n=1$, but for an arbitrary $n$?? Where can I find the points per game throughout many NBA seasons? Where can I find the points per game (of both teams) throughout many NBA seasons?  To illustrate my point, what I mean is something like:   2000/01 average points per NBA game: 200; 2001/02 average points per NBA game: 210; 2002/03 average points per NBA game: 205;   so on... Array of zero length I am working on refactoring some old code and have found few structs containing zero length arrays (below). Warnings depressed by pragma, of course, but I've failed to create by "new" structures containing such structures (error 2233). Array 'byData' used as pointer, but why not to use pointer instead? or array of length 1? And of course, no comments were added to make me enjoy the process...  Any causes to use such thing? Any advice in refactoring those?  struct someData {    int nData;    BYTE byData[0]; }   NB It's C++, Windows XP, VS 2003 Where to find the checksums of Ubuntu ISO images? I just downloaded the ubuntu-10.10-desktop-i386.iso, and am having a hard time burning it, so I'd like to check that the file is intact, but I cannot find the md5sum of the file.    Is there a URL or official FTP mirror which includes the md5sum of the Ubuntu disk images? I have been trying to install the latest version of java-8. However, I found out that the  due to changes in the java licence.  How should I update my java to 8.0_201 or 8.0_211 now?  Thanks! How do you pull first 100 characters of a string in PHP Solving a Diophantine equation with a large solution I've run across (personally or by proxy) a bunch of storage media that exhibited physical problems during their life. Hard disks, solid state drives and other flash storage media all fail after some time. The situation is worse with USB flash drives and flash cards because of the large amount of suppliers with inferior flash cell and flash controller quality.  How can I reliably detect if a storage drive suffers from physical damage?  Note that this question isn't about file system integrity (which can be checked with ). Why is the year NOT displayed in the questions and comments dates? Why is it that the year is never displayed in the questions or comments? Is it because it is the current year? I, and maybe others, wonder. I'm looking for a word that describes a person who is extremely dismissive and unopen to ideas or comments. Dismissive  feeling or showing that something is unworthy of consideration   For example,  Tom: 'Get your table organised! It's so-' Jack: 'Shush, bring your comments somewhere else.' Is it possible for an iPad to get a virus? A high school Olympiad problem I put all my music on a playlist seperate from the rest of the music on the iTunes library, so I could easily get to what music I wanted to listen to, instead of my brother or sister's music. My brother recently got an iPod nano, and didn't know how to use iTunes, after explaining it to him, he deleted my whole entire playlist. I didn't know, so when I hooked my phone up to the computer to sync some songs I was going to buy, all the music on my phone disappeared. I've tried re-doing the playlist and syncing all of it to my phone again, but it won't work. I've also tried turning off my phone for certain periods of time, still nothing.  I lost about 200 songs (thankfully not more), and I don't know how to get it back. Generic htaccess redirect www to non-www I would like to redirect www.example.com to example.com. The following htaccess code makes this happen:  RewriteCond %{HTTP_HOST} ^www\.example\.com [NC] RewriteRule ^(.*)$ http://example.com/$1 [L,R=301]   But, is there a way to do this in a generic fashion without hardcoding the domain name? Can I watch the progress of a `sync` operation? I've copied a large file to a USB disk mounted on a Linux system with async. This returns to a command prompt relatively quickly, but when I type sync, of course, it all has to go to disk, and that takes a long time.  I understand that it's going to be slow, but is there somewhere where I can watch a counter go down to zero? Watching buffers in top doesn't help. I have to determine how many six-integer subsets of $\{1, 2, 3, \ldots, 20\}$ are possible if no two consecutive integers are in a set. Numbers to the Power of Zero Notify question OP (and those who marked it a favourite) if an answer has been modified Seriously, I had not noticed e.g. Jeff's edit  had he not also retagged my question.