I updated my Ubuntu 12.04 server yesterday with the latest updates and now when Ubuntu starts it is in a really strange state.  A purple screen comes up but there are no Unity icons and I can't really do anything, there are no errors that I can detect.    I've never really had any issues like this with Ubuntu so I'm a bit unsure how to get it resolved, my Linux commannd line knowlege is somewhat limited so any details would be greatly appreciated in attempting to debug.    Is there any way to rollback recent updates?  Does anyone have any suggestions for troubleshoting or have any ideas on what could be the issue?   Any help or suggestions would be greatly appreciated.    Thanks.
My Ubuntu 12.04 was normally updated through the Update Manager, something about gtk. Then I rebooted and now all that shows after the splash screen is a blue screen that only shows the cursor.
How do you prove the  from statistical mechanics? To prove entropy will only increase with time? How to prove? Please guide. Where is the flaw in this "proof" that 1=2? (Derivative of repeated addition) Consider the following:   $1 = 1^2$ $2 + 2 = 2^2$ $3 + 3 + 3 = 3^2$   Therefore,   $\underbrace{x + x + x + \ldots + x}_{x \textrm{ times}}= x^2$   Take the derivative of lhs and rhs and we get:   $\underbrace{1 + 1 + 1 + \ldots + 1}_{x \textrm{ times}} = 2x$   Which simplifies to:   $x = 2x$   and hence    $1 = 2$.     Clearly something is wrong but I am unable pinpoint my mistake. What causes the expansion of space? Writing string at the same position using Console.Write in C# 2.0 Is there a reason why ls does not have a --zero or -0 option Dissolve (merge) polygons QGIS based on attribute values only when are adjacent Usually, in Star Trek, when there's a timeline change, the indication is that the original timeline is gone and replaced with the new one.  In City on the Edge of Forever, Kirk makes a comment that if they don't get the timeline straight, that millions of people who never died before will die.  Much of the time travel in Trek created suspense by declaring a need to restore the original timeline.  It's already been discussed in other questions about how, in the new movie (simply titled Star Trek with no subtitle or series number) they were unable to restore the original timeline.  While some of this is open to interpretation, it seemed like in this instance, for the first time, in Trek, there was an alternate timeline that was seen as an alternate possibility - no reference was made to it replacing the original timeline.  In this movie, was there any reference to the original timeline still existing?  In this movie, was the original timeline still considered to be intact? Add bst file with LaTeX / MiKTeX I'm trying to use elsarticle-num-ident.bst, an exact copy of  C:\Program Files (x86)\MiKTeX 2.9\bibtex\bst\elsarticle\elsarticle-num.bst    but every time I run LyX, I get the bibtex error  I couldn't open style file elsarticle-num-ident.bst   This is despite reconfiguring LyX and restarting, and despite running MixTex's Settings/Options' "Refresh FNDB" as Administrator.  It also doesn't work if I put the .bst file in the same folder as the .lyx file.  How should I help lyx/bibtex/Mixtex find the .bst file?  Once I get the identical copy to work, I plan to edit it to not print URLs, as suggested .  Related questions: Keyboard key stuck or not being recognized; how to fix Getting CalloutException when testing Batchable class with Callouts and HttpCalloutMock Is there a quasistatic process that is not reversible? I have seen several questions and good answers on the link between reversible and quasistatic processes, such as  or . However, these questions only adress one side of the problem : a reversible process is necessarily quasistatic.  I am interested in the other side of the equivalence : is there a process that is quasistatic, yet not reversible ? It looks to me that an irreversible process cannot be made perfectly quasistatic.  The  article about quasistatic processes takes as an example the very slow compression of a gas with friction. As the compression occurs very slowly, the transformation is quasistatic, and the friction makes it irreversible. I am not convinced by this example : if you press on the piston with a vanishingly small force you will have to reach the threshold of the Coulomb law for solid friction before moving the piston anyway. It makes the process non-quasi-static, however small the Coulomb threshold might be.  Another example I've heard of is the reaction between a strong acid and a strong base. It is always an irreversible process, and you could make it quasistatic by adding very small drops of base into acid at a time. But by trying to do that, you would inevitably reach a limit to the size of the drop imposed by surface tension.  Even if "reversible" and "quasistatic" mean very different things, is it true to consider that in practice, a reversible process and a quasistatic process is essentially the same thing ? Suppose I sold an option on stock X, with strike price Y, and expiry date Z. Suppose I later buy an option on the same stock, with the same strike price, and the same expiry date. Do these two positions cancel out each other (i.e. both contracts cease to exist anywhere), or will I end up with two separate contracts?  Is it the same with the reverse situation? e.g. I bought an option on stock A, with strike price B, and expiry date C. If I later sell an option on the same stock, with the same strike price and expiry date, will I end up with two contracts (one long position, one short position)? I use Firefox 35.0 on my Macbook to access Stack Exchange. Recently whenever I access a message or Community site, the "spinning circle" indicating activity starts, and never stops. This doesn't seem to happen on other non-Stack Exchange sites.  Has there been any change to the SE code which may have caused this.    The Web Developer Console shows  The connection to ws://qa.sockets.stackexchange.com/ was interrupted while the page was loading. full.en.js:1 Use of getPreventDefault() is deprecated.  Use defaultPrevented instead. jquery.min.js:3 How to find previous boot log after Ubuntu 16.04+ restarts? My question is, how can I find boot log from previous system boot attempt?  Today when first powering on my PC, boot process stopped on Ubuntu logo, when I pressed Esc I have seen several lines containing some kernel error and restart required at the bottom, so I pressed Ctrl+ALt+Del and next boot went OK without problems.  I have trouble finding messages from the screen I have seen during the first unsuccessful boot. Should I have taken picture to my phone?  /var/log/boot is there but empty, I searched  and  for strings I remembered with today's date like error but found nothing familiar to what I have seen on previous boot screen.  $ journalctl -b -1 gives me only kernel messages during boot, I can find that elsewhere too, and they are not what was appearing on screen during boot, journalctl is useless for me, I am looking for messages appearing on screen during boot time.  For now, only option is take a photo of write the message on paper. This is a general, community wiki  question and answer pair intended to address any questions   concerning the reasons a site or specific site contents do not appear   in search engine results.      If your question was closed as a duplicate of this question and you   feel that the information provided here does not provide a sufficient   answer, please open a discussion on .   My site (or specific pages on my site) is not appearing in search engine results.  Why isn't my content indexed and what can I do about it? Why do I need multiple sites for the same property in Google Webmaster Tools? In researching the best practice for adding sites to the Search Console, I've often seen it suggested to add separate properties for different versions of the same website. Even in  it states:     "Similarly, if your site has http:// and https:// versions, you should   add each as a separate site."   I've seen the same suggested for www/non-www. So if a site is accessible at all the variations of http/s and www/non-www we should have four properties.  But what if the site is only accessible at one variant? i.e. https and www are forced via htaccess, so only  can ever be accessed - should we still add all the variants?   In essence, the problem is that I don't know why Google wants us to do this, so I can't work out if it'll be ok just to have one instance. Pigeonhole-principle with two choices I am able to solve this sort of problem pretty easily.     An arm wrestler is the champion for a period of 75 hours. The arm   wrestler had at least one match an hour, but no more than 125 total   matches. Show that there is a period of consecutive hours during which   the arm wrestler had exactly 24 matches.   However this homework problem I can't seem to figure out.     Tyler has five weeks to prepare for his driver’s test. His mother   volunteers to ride with him for either 15 minutes or one half hour   every day until the test but not for more than 15 hours in all. Show   that during some period of consecutive days, Tyler and his mother will   drive for exactly 8.75 hours.   If I try doing it the same way as the first problem. I get $70$ pigeons and $95$ pigeon holes. I honestly don't know where to start with this problem. I thought that maybe I could assume that they only drove $.25$ hours on each day and prove that there is a period of consecutive days where they drove for exactly $8.75$ hours. Then I could say that we assume there is one day that they drove for $.5$ hours and work my way up, but I can't seem to get that to work either. I would like to remove my Raspberry Pi from my iPhone 8 (running iOS 11.2.1) as a connected bluetooth device.  Normally, I would go into my Settings -> Bluetooth and select the Info button (a small blue circled "i") to show the "Disconnect" and "Forget Device" dialogs:    Unfortunately, iOS does not give me this option for my device. The bluetooth device list does not contain an "i" for the item, and there is seemingly no other way to disconnect.    How do I unpair this device if there is no button to trigger to the unpair prompt?  Due to work restrictions I cannot completely reset the device. How to find out if my system is i386 or x86_64 before installing Ubuntu? I am using Windows as of now and want to install Ubuntu. I want to find out if my system is i386 or x86_64? How do I do that? Where can I find the status of the released versions of Ubuntu? I want to know where I can find updated information about all the stable and in-development versions of Ubuntu, where I can find this information?     This question is meant to be a canonical question. It expects to answer the following questions:         Is X version stable yet?   Is X version in beta?   Is X version still supported?   What versions are still supported?   What are the versions in Beta/Alpha?   Until where X version will be supported?   Have X version ceased support?   When will be X version released?   Where I can download any release?   When will the next LTS version of Ubuntu be released?         The list is not exhaustive.