Ubuntu 14.04 to 18.04 do-release-upgrade: "No new release found" I have a problem while upgrading from Ubuntu 14.04 to 18.04. We have few thousand devices on Ubuntu 14.04 that need to be upgraded to 18.04. I have tried to upgrade to  16.04 first. But when I try do-release-upgrade I get &quot;No new release found&quot;. What I'm trying is below. ## edit /etc/update-manager/release-upgrades, change never as lts sed -i &quot;/Prompt=/c\Prompt=lts&quot; /etc/update-manager/release-upgrades  ## to make dpkg continue non-interactively echo &quot;force-confdef&quot; &gt;&gt; /etc/dpkg/dpkg.conf echo &quot;force-confold&quot; &gt;&gt; /etc/dpkg/dpkg.conf  # to upgrade non-interactively  export DEBIAN_FRONTEND=noninteractive  ## update, upgrade and do-release-upgrade apt-get -o Dpkg::Options::=&quot;--force-confdef&quot; -o Dpkg::Options::=&quot;--force-confold&quot; upgrade apt-get -o Dpkg::Options::=&quot;--force-confdef&quot; -o Dpkg::Options::=&quot;--force-confold&quot; dist-upgrade do-release-upgrade -d -f DistUpgradeViewNonInteractive
How to install software or upgrade from an old unsupported release? Recently I have installed an older version of Ubuntu on my old machine. Whenever I try to install any software, I get an error saying it couldn't be found:  $ sudo apt-get install vlc Reading package lists... Done                Building dependency tree        Reading state information... Done     E: Couldn't find package vlc
Preview: PDF Highlighting & Search Stop Working until Restart A problem has recently become much more prevalent for me when using Preview to search PDFs for text (using Command + F or the search box in the upper right).  At first, everything generally seems to go fine:    (as it should be) a list of thumbnails appears in the sidebar, indicating all of the pages that contain the search term. Generally, though not always, the term I search for will be highlighted on the first page that it occurs on.   But, after this, things quickly start malfunctioning:   Generally speaking, if I click on thumbnails lower on the list, Preview will take me to that page in the PDF (like it used to).  But, it will no longer highlight the searched for terms. Instead, Preview will make a low-pitched beeping noise of the sort that occurs when one tries to perform some un-permitted action in a variety of mac situations. Furthermore, once this occurs, I cease being able to make any highlights at all in the document I am viewing with Preview.  In fact, I can't even select any text any more.   Below is a list of unsuccessful efforts to resolve this:   Closing the side bar does not work to resolve this. x-ing out the search box in the upper right does not resolve this. Selecting the "Tools" menu and then "Text Selection" does not work either, nor does clicking on the text selection icon in the edit panel. If I quit preview and then re-open the PDF, I am able to highlight again.  But, the problem will re-surface as soon as I try performing another search. Working with the same files in other PDF programs (e.g. Skim, Acrobat, etc.) poses no problems.  I'm quite certain it isn't a problem with the underlying PDFs. None of the responses to  resolve this.  (indeed, I supplied one such response myself a while ago, but that trick and the others no longer work).   I've used Preview for many years without problem.  This issue started cropping up relatively recently for me, I believe within the past 3-4 months.  I had hoped that upgrading to Catalina might resolve it, but it did not.    I'd like to think I am fairly sophisticated with computers (I have a reputation of close to 8,000 on the main stackoverflow page), but I am baffled by this.  I also don't have a good handle on how I can get diagnostic information or how I can create a reproducible example.    Any leads on how to tackle this would be greatly appreciated. bash regex with quotes? The following code  number=1 if [[ $number =~ [0-9] ]] then   echo matched fi   works. If I try to use quotes in the regex, however, it stops:  number=1 if [[ $number =~ "[0-9]" ]] then   echo matched fi   I tried "\[0-9\]", too. What am I missing?  Funnily enough,  suggests this should work.  Bash version 3.2.39. mkfs on raw software raid device or partition I am making a huge RAID10 device (8 TB) for storage on CentOS. I have created the 4 partitions on my 4 physical hard disks and have created the raid device /dev/md2 out of those 4 partitions.  Now it's time to put a filesystem on it. I am wondering whether I should do just:  mkfs.ext4 /dev/md2   which totally works (I tried it), or I should first create a single partition on that device (with fdisk, gdisk or parted?), that takes up all the space, and then do the mkfs stuff on that partition.  Googling the Web, I found another person asking the very same question here:  but, although a responder said:      Partitions go on the array members.   Filesystem goes on the array.   they didn't give him a definitive, non-ambiguous answer or an explanation when one approach should be preferred over the other. check the availability of the WCF Web Service I want to check the availability of the WCF web service i.c service is up or down through  the C# code. How to achieve that? Can a Stack Exchange association bonus be lost? I recently hit 200 rep on Stack Overflow and got a big 100 rep bonus. Most know this as the 'association bonus'.  If I offer a bounty of 50 points and thereby lessen my 'base' score, do I lose that association bonus?  What if I offer a 150 point bounty and then work my way back to 200? How to prove that the ideal $I=(x^3-y^2)$ in $k[x,y]$ is prime?    I have constructed a map from $k[x,y]$ to $k[t]$, which maps $x$ to $t^2$, and $y$ to $t^3$. Then, I want to show that the kernel is exactly $I$. But the difficulty is that how to prove the kernel is contained in $I$.  Could you help me? Thanks a lot! Anonymous Types - Are there any distingushing characteristics? Is there anything to use, to determine if a type is actually a anonymous type? For example an interface, etc?  The goal is to create something like the following...  //defined like... public static T Get&lt;T&gt;(this IAnonymous obj, string prop) {     return (T)obj.GetType().GetProperty(prop).GetValue(obj, null); } //...  //And then used like... var something = new { name = "John", age = 25 }; int age = something.Get&lt;int&gt;("age");   Or is that just the beauty of an anonymous type? Nothing to identify it self because it takes a new shape?  Note - I realize that you can write an extension method for the object class, but that seems like a little overkill, in my opinion. How to count number of words from String using shell I am looking for a correct proof of this statement: If $G$ is a group such that $G/Z(G)$ is cyclic, then $G$ is commutative.  Proof: $G/Z(G)$ is isomorphic to $\operatorname{Inn}(G)$ and is cyclic, and then for every $a$ and $b$ in $G$ the inner isomorphisms $\gamma_a$ and $\gamma_b$ satisfy $\gamma_a \gamma_b = \gamma_{ab} = \gamma_{ba} = \gamma_b \gamma_a$, and therefore for every $a,b \in G$, $ab = ba$.  Is that proof complete, or am I missing something? Thanks a lot for the help. How can I pass a class member function as a callback? Add a duplicate:0|1 search operator I often search for closed questions and sift through the ones that are not duplicates to see if any of them need to be killed. Technically, closure is the first step towards deletion and the only closed posts that are actually useful are duplicates (unless it's a crappy one).  For the rest, if the community hasn't bothered to reopen it after a while or if the OP has made no effort to edit their question, I delete it if it has no redeeming content. For example, the only closed posts seen on  are exact dupes.  But this does become tedious when there are several results for various close reasons with duplicates interspersed between them. I'd like to be able to search as:  closed:1 duplicate:0   so that it gives a list of questions closed as OT/NaRQ/NC/TL. This will be similar in behaviour to migrated:0|1.   This will also be useful for 10k+ users on all sites (2k+ in beta) in the network, especially SO, so that they can search for questions to spend their delete votes on— especially closed, non-dupe questions in the tag they specialize in. More often than not, I hesitate to vote on questions that are outside my area of interest (unless it is crappy). Is the Ministry of Magic unable to detect illegal time-tampering? Since Hermione already admitted that they were breaking the Law. Would it be safe to conclude that the Ministry cannot instantly (by magic) detect illegal time-tampering?  (Both before and during the events of Prisoner of Azkaban.)     “Hermione,” said Harry suddenly, “what if we — we just run in    there and grab Pettigrew —”       “No!” said Hermione in a terrified whisper. “Don’t you understand?    We’re breaking one of the most important wizarding laws!    Nobody’s supposed to change time, nobody! You heard Dumbledore,    if we’re seen —”       — Prisoner of Azkaban, chapter 21 (Hermione’s Secret) Can we implement temporary automatic comment ban on 'x' number of validated rude comment flags? There's been problems with abusive comments since the site started.   We still haven't managed to conquer the issue.   Users can be issued chat bans and post bans. The API automatically bans IP addresses with validated spam flags. (Would it be difficult to implement comment bans? Would mods have the power to impose comment restrictions?).   Although comments have been classically referred to as second class citizens, rude comments on the site are the one place that is driving people away.   Can we implement temporary automatic comment ban on 'x' number of validated rude comment flags? It would probably be better if the exact heuristics were not disclosed publicly, much like the serial voting scripts  This question  was asked 7 years ago. Can we revisit it?  This question is related, but is asking for a more complex approach: While browsing on Safari and listening to iTunes I come across a video and then press the "play" button on the keyboard (to stop the music while I watch the video) it starts/stops the video instead of the music (I have no control over the music).  How can I quickly play/pause my music without affecting the video? Omitting 'that' in this sentence Consider $X = (a+b)^n-a^n-b^n$  where  $a$ and $b$ and $a+b$ are not divisible by $n$, $n&gt;=3$ is positive and prime, $a \ne b$ and both are greater than 1.  By the binomial expansion we know $X$ is divisible by $n$, but how can we study whether $X$ is divisible by $n^2$ or other powers of $n$? Specifically I am interested to prove $X$ is NOT divisible by $n^2$, but I am not sure how to prove or disprove it. Nautilus doesn't launch on Ubuntu Take the manifold: The graph of $|x|$ on $(-1,1)$, with the induced topology from $\mathbb{R}^2$. This is a topological manifold, which is homeomorphic to $(-1,1)$ by projection. Is it a differentiable manifold? I believe it is, because we can take an atlas with only the projection, and then we will have only one transition map which is the identity, and therefore differentiable. But I'm not sure I get the definition of a differentiable manifold right...  Thanks! Let ($x_s$) be a convergent sequence, where $x_s&gt;0$ for all s, and $y_s$ be a sequence such that   $$\displaystyle \Large y_s=\frac{s}{\frac{1}{x_1}+...+\frac{1}{x_s}}$$  Prove $\displaystyle \lim x_s$=$\lim y_s$  So I know things like $x_s$ is bounded, and that it's Cauchy, but I can't think of anything to solve it.  Any help is appreciated. VirtualBox error kernel headers I'm with Ubuntu 15.04 and I'm trying to create an emulator (genymotion), but when run virtualbox, i got the error:     Stopping VirtualBox kernel modules ...done.   Uninstalling old VirtualBox DKMS kernel modules ...done.   Trying to register the VirtualBox kernel modules using DKMSError! Your kernel headers for kernel 3.16.0-30-generic cannot be found.   Please install the linux-headers-3.16.0-30-generic package,   or use the --kernelsourcedir option to tell DKMS where it's located    ...failed!     (Failed, trying without DKMS)   Recompiling VirtualBox kernel modules ...failed!     (Look at /var/log/vbox-install.log to find out what went wrong)   I performed   uname -a   And the result is:     Linux douglas 3.16.0-30-generic #40-Ubuntu SMP Mon Jan 12 22:06:37 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux   Someone help me?Already I uninstalled and installed again.