Is there a way to purge all packages installed via apt-get from the very moment you installed the Ubuntu OS, up till this very point?  One could call it a a "mega apt-get purge".  The purpose of this operation to clear the system of everything I've installed so far (from apt) on top of the Ubuntu OS itself. This would bring me the closer to a fresh install of a Ubuntu OS, without any added software (of course, the only thing I'll have left is to clear all non-apt software and individual files I've added, but that is of course another issue).  The reason for this operation is because this is done on a VPS machine in which I can't install and uninstall operating systems in the traditional way; I can indeed use the "rebuild" functionality of my hosting provider but I find it a bit annoying to use from personal reasons so I just want to go closest I can to a fresh install without that.  How will you do the desired "mega apt-get purge"? Thanks.
I'd like to get a list of packages installed manually by apt or aptitude and be able to find out whether a foobar package was installed manually or automatically. Is there any neat way of doing that from the command line?
The following code best describes the situation.  Why is the last line not outputting the trailing newline char?  Each line's output is shown in the comment.  I'm using GNU bash, version 4.1.5          echo -n $'a\nb\n'                  | xxd -p  # 610a620a              x=$'a\nb\n'   ; echo -n "$x" | xxd -p  # 610a620a      echo -ne "a\nb\n"                  | xxd -p  # 610a620a x="$(echo -ne "a\nb\n")" ; echo -n "$x" | xxd -p  # 610a62 How to resolve BackgroundContainer.dll error on startup? When I start my desktop it gives me an error about BackgroundContainer.dll.    How to get rid of it?  I found nothing when i started regedit.exe and searched (F3 or CTRL+F) for BackgroundContainer.dll What is this shell/Bash syntax: someVariable=someValue someCommand Java - How to reduce the size of third-party jars to reduce the size of your application What does "Could not find or load main class" mean? Mathematical notation around the world Why are my SVG imports so small? When and where do I have the highest chance of seeing auroras? I'm wondering what time of year is best, and what locations might be best, for catching the aurora.  I'm currently thinking of February up at Sweden's ice hotel, but since the whole point of the trip is so that my wife can see the Aurora, I want to pick a location that affords the best chances to see one.  Edit: Just adding a link so you can see realtime aurora activity in the northern hemisphere    I know this is anecdotal, but I ended up going to Iceland in late february during the new moon and saw the aurora 3 out of 6 nights I was there.  There was activity every single night but the biggest problem was weather.  It was cloudy almost every single night. mysterious error: \pdfendlink ended up in different nesting level than \pdfstartlink I ran into the "mysterious"  \pdfendlink ended up in different nesting level than \pdfstartlink   error.  According to , "this happens when hyperref is used under pdftex and a citation splits across a page boundary".  The given solution is to manual fix the citation to not split across the page boundary.  However, this workaround isn't feasible for me, as the documents are automatically generated on a server with no user interaction.  Is there any solution to the problem known, perhaps an experimental hyperref action or a patch to pdftex?  (Probably, one could use luatex to solve the problem, but for other reasons, luatex is not an option in this project.)  MWE:  \documentclass[%draft               ]{article} \usepackage{hyperref} \setlength{\textwidth}{3cm} \setlength{\textheight}{3cm}  \begin{document} Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna \href{http://www.tug.org/errors}{aliquyam erat, sed diam voluptua.} \end{document} Windows 8 disk usage is 100% How can I know if my macbook is hacked? I want to append some data to a layer in my PostGIS DB using a shapefile, but when I use the Import layer/file tool in QGIS, it doesn't allow me to choose the append option.  Why is this and how do I get it to allow me to append? I know that who is used when asking about a subject (Who is at the door?) and whom is used when asking about an object (By whom was the door opened?). How do you determine which one to use when the object becomes the subject of another clause?   For example, take the sentence:      I gave the prize to ____ deserved it most.   Would it be whomever because it's the object of "gave," or would it be whoever because it's the subject of "deserved"? Is their a hard-and-fast rule to rely on in situations like this? Since a few months, on one of the desktop Ubuntu 14.04 systems I use, CPU has regularly been going up to 80-100% for no apparent reason. htop would usually attribute responsability to file system processes, such as nemo or ntfs. To get CPU back down I would kill these process, which in some cases would lead to loss of access to the file system and a consequent restart.  Days ago I noticed that whenever this situation happened another process was always present also using high CPU: mediascanner-service-2.0. Some research lead me to  that simply advised its removal. So I did.  The end result has been unexpectedly positive: not only are the high CPU load episodes gone, the system is altogether much faster. The speed up of the Lens is dramatic: finding an application like Calc now takes 2 seconds at most when previously it took some 20 seconds. Finding a file takes now some 5 seconds, whereas before it took in the order of 30 seconds. Heavy programmes like Eclipse are starting up faster and workspaces are more fluid. There seems to be also an overall reduction in the frequency of disk access.  What is exactly this mediascanner2.0 package? Is it part of Unity 7 or a dependency that gets installed a posteriori? Is it possible to prevent its installation?  Update: following  it is possible to track this package down to indicator-session:  $ sudo aptitude why mediascanner2.0 i   indicator-session         Recommends indicator-applet (&gt;= 0.2) | indicator-renderer i A unity8                    Provides   indicator-renderer                             i A unity8                    Recommends unity-scope-mediascanner2                      pi  unity-scope-mediascanner2 Depends    mediascanner2.0                                  Apparently, mediascanner2.0 (and the Unity 8 shell) are part of the base 14.04 system. Left to answer is the exact function of this rogue package. In January, some additional whitespace  below h1, h2 and h3 headings,  more whitespace below the headers than above them.  Could we have the whitespace above the headings be more than the whitespace below them?  I find some posts a bit hard to read, like the current rendering on the left:   &nbsp; &nbsp; &nbsp; What is the name of a squircle with three, five, six or more corners? I know that the second shape is a squircle, but what are the other shapes called? Is there an actual name for them?    The shapes do not simply have rounded corners, but the sides have a "circularity". Here is a triangle with rounded corners next to the shape that I do not know the name of:    "Trircle", "Triarcle", and "Pentircle" do not seem to be used for them, at least Google's image search does not provide any results. How can you enumerate an enum in C#?  E.g. the following code does not compile:  public enum Suit {     Spades,     Hearts,     Clubs,     Diamonds }  public void EnumerateAllSuitsDemoMethod() {     foreach (Suit suit in Suit)     {         DoSomething(suit);     } }   And it gives the following compile-time error:     'Suit' is a 'type' but is used like a 'variable'   It fails on the Suit keyword, the second one. Install GNOME Shell extensions from terminal Is there a way to install GNOME extensions from terminal, for example dash to dock? The way I do it now is to go into Ubuntu Software app store and install it. round in PHP shows scientific notation instead of full number I'm trying to do an echo of a variable containing 1400000.  so there is written: echo round(1400000); this gives 1,4E+6 instead of the full number. Anybody an idea on how to display it fully? How to run applications as root? I am having some strange issue with Kate and Kwrite. When I click on Open File, it crashes with segmentation fault.   I am a complete newbie to Linux, and I think the issue is that I am not running the application as root.   How do I run applications as root in Ubuntu? Is it bad practice to do this? What is the purpose of the whole root thing, where even though we need to use root so frequently, it is not utilized as default?