I upgraded successfully. Now, when I run this:  dpkg --list | grep linux-image   I get this:  ii  linux-image-3.13.0-24-generic                               3.13.0-24.47                                                amd64        Linux kernel image for version 3.13.0 on 64 bit x86 SMP rc  linux-image-4.4.0-31-generic                                4.4.0-31.50                                                 amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP ii  linux-image-4.4.0-34-generic                                4.4.0-34.53                                                 amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP ii  linux-image-4.4.0-36-generic                                4.4.0-36.55                                                 amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP ii  linux-image-extra-3.13.0-24-generic                         3.13.0-24.47                                                amd64        Linux kernel extra modules for version 3.13.0 on 64 bit x86 SMP rc  linux-image-extra-4.4.0-31-generic                          4.4.0-31.50                                                 amd64        Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP ii  linux-image-extra-4.4.0-34-generic                          4.4.0-34.53                                                 amd64        Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP ii  linux-image-extra-4.4.0-36-generic                          4.4.0-36.55                                                 amd64        Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP ii  linux-image-generic                                         4.4.0.36.38                                                 amd64        Generic Linux kernel image   So my question is: What do I do with all the extra modules? Do I trash them? If so, how? or do I keep them?
I occasionally update my kernel from this web site    I have been always downloading 3 deb files for installing  linux header all, linux image and linux headers. I noticed one more deb file recently for 64 bit kernel called Linux-image-extra.  I would like to know what does kernel file Linux-image-extra do and should I also install it?
I was thinking about writing a partial derivative macro that has a similar syntax to the . ()  The syntax could be like this:   \D{f}{x} expands to \frac{\partial f}{\partial x} \D{f}{x,y} expands to \frac{\partial^2 f}{\partial x\,\partial y} \D{f}{{x,2},y} expands to  \frac{\partial^3 f}{\partial x^2\,\partial y} et cetera for any number of derivatives.   Bonus points for an optional argument so that for instance   \D[subscript]{f}{{x,2},y} expands to f_{xxy}   I looked at the  package but the syntax is a little tedious.  For instance, to get \frac{\partial^3 f}{\partial x^2\,\partial y} with that package I would need to do \md{f}{3}{x}{2}{y}{}.  And it doesn't generalize to three variables.  Before I dive in I thought I'd ask the hive and see what's been done. How does the Golden Ratio/Spiral Work? Is it useful with Logo Design? Discrepency in unanswered questions counts On , I notice that if I use the lower &quot;unanswered&quot; tab (the one in line with &quot;All Questions&quot;), the count is 1,432 questions. If I use the upper &quot;Unanswered&quot; tab (in line with the site title), I get 1,383 &quot;questions with no upvoted or accepted answers&quot;.  This changes the options in the lower tab, one of which is &quot;no answers&quot;.  Clicking here, I now get 1,083 &quot;questions with no answers&quot;. If I run select Id from Posts where PostTypeId=1 and AnswerCount=0;  in the , I get 1158 rows back. Which of these is correct, and why is the first one (1,432) so much higher than the others?  I understand that the numbers may only be updated periodically, but that difference in particular seems much too great for this to be the reason. To clarify:  1,432 is the number of &quot;unanswered questions&quot;. 1,383 is the number of &quot;questions with no upvoted or accepted answers&quot;. 1,083 is the number of &quot;questions with no answer&quot; 1,158 is the number of questions with no answer in the data explorer.  This is not live data, but that means it should be smaller, not larger, than 1,083.  I promise we did not offset this with answers to the tune of 80 questions this week.  The first three are obviously live because they fluctuate. The difference between the first two is ~50, implying they actually don't refer to the same thing, and the difference between the last two seems too great (and in the wrong direction) to be explained by the a live vs. data explorer source. The StackExchange™ MultiCollider SuperDropdown™ says I've got replies, but I've already viewed those. If you activated a free upgrade to Windows 10 or bought and activated   Windows 10 from the Microsoft Store, you have a digital license for   your device. This means you can reinstall the same edition of Windows   10 that your device has a digital license for without entering a   product key. During reinstallation, if you’re asked to enter a product   key, you can skip this step. Windows 10 will automatically activate   online after the installation is complete.   source:   Does MS digital license 'fingerprint' hardware information  during the free upgrade / activation and store it (at Microsoft) , so that the next re-install queries MS for the fingerprint and activates Windows 10?  Thought the disk drive may change, I expect that none of the other fingerprinted hardware will change. True Definition of the Real Numbers I've found lots of resources that say this is a real number if it's not rational, but what is a real number, really?  I mean what is the definition of a real number?  If nothing else, anyone know of a resource where I could find out myself?  Thanks! What's the "official" explanation for Harry's (and everyone else's) absence from muggle school? I need to prove that $K\subseteq \mathbb{R}^n$ is a compact space iff every continuous function  in $K$ is bounded.  One direction is obvious because of Weierstrass theorem. How can i prove the other direction? I tried to assume the opposite but it didn't work for me.  Thanks a lot. Read fixed width record from text file Why is my attempt at downloading Big Sur failing? I am currently using a MacBook Pro 13&quot; Mid 2018 with Touch Bar. Today macOS Big Sur was released and I tried to download it but it's getting stuck at 484.4 MB. Initially, it shows 16-17 minutes left, but as soon as it reaches 484.4 MB it's stuck and the timer goes till 10 hours! My Wi-Fi is totally stable with a speed of 100 Mbps. I tried to restart my Mac but it still gets stuck. Earlier there were similar issues in the App Store (even now they are). The issue was I was not able to download an app unless I connect to the US VPN. I even contacted support but they were not able to help out. It wasn't a big deal as a VPN could be used. But now even with VPN, it gets stuck. "done" vs "have done" The word that always gets me mixed up : JUST I had just arrived at the hotel, checked in and gotten into my room. Just as I was about to unpack, I noticed that one of my bags was missing. At first I thought I had left it back at the airport, but it turned out that I had left it on the taxi.  Here, what's the meaning and role of "just"?  Why do you guys input the word "just" here?  What exactly does the word do grammatically?   Could you help me? Let $M_n$ denote the vector space of all $n\times n$ real valued matrices and for any matrix $A\in M_n$ let $A^t$ denote its transpose. Define the linear map $T:M_n\rightarrow M_n$ as $$T(A)=A+A^t.$$ What is the minimal polynomial of $T$? What are the eigenvalues and the corresponding eigenspaces of $T$? What is the characteristic polynomial of $T$?  I learned about minimal polynomials of operators from $\textit{Linear Algebra Done Right}$ by Axler. In his description he explains how in order to find the minimal polynomial you must find the smallest positive integer $m$ such that $T^m$ is a linear combination of $I, T, T^2, \ldots, T^{m-1}$. That is, the smallest integer $m$ such that $$T^m = a_0I+a_1T+a_2T^2+ \cdots +a_{m-1}T^{m-1}.$$  As for the eigenvalues...since we are working with real-valued matrices, then $A$ and $A^t$ have the same eigenvalues, so if $\lambda \in \mathbb{R}$ is an eigenvalue of $A$ (and hence of $A^t$) wouldn't $2\lambda$ be an eigenvalue of $A+A^t$? I apologize if I am saying utter nonsense... Can I force a link to open in a specific browser? What does -y mean in apt-get -y install command? I always see commands like this  apt-get -y install    What is the -y tag for and what is the difference between apt-get install with and without the -y tag? How can I attach a file to a question? Prove: $|a\sin x+b \cos x|\leq \sqrt{a^2+b^2}$ $$|a\sin x+b \cos x|\leq \sqrt{a^2+b^2}$$   I have tried: $$|a\sin x+b \cos x|\leq |a+b|\leq \sqrt{a^2+b^2}$$  enough to prove: $$|a+b|\leq \sqrt{a^2+b^2}$$  But I can find how to continue from here StructureMap error when invalid controller I am using Structure map like the MVC storefront by Rob Conery does and I have an AdminController and so to get to it I just type:  website/Admin/action   however if I miss spell the controller name I get the error below:  Exception Details: System.ArgumentNullException: Value cannot be null. Parameter name: key  There error occurs on this line:  Controller controller = ObjectFactory.GetInstance(controllerType) as Controller;   Does anyone have any ideas on how I can handle this error or not allow it to happen at all and maybe just goto a 404 page??  Cheers in advance How can I delete everything from my MacBook Pro before selling it? I have a Mac that runs Snow Leopard and I intend to upgrade it to Mountain Lion and sell it on ebay. However, I only have one hard-drive, and I'm sure I can't use something in my OS to delete my OS and all user data.  Is there something for this that's built into the firmware that I can do on boot, or otherwise?   I have source code on my Mac for multiple corporations' proprietary software and I can't risk somebody gaining access through the use of any sort of disk recovery tool. I plan to use a 7 pass erase rather than simply deleting the directory. Regular cast vs. static_cast vs. dynamic_cast I've been writing C and C++ code for almost twenty years, but there's one aspect of these languages that I've never really understood. I've obviously used regular casts i.e.  MyClass *m = (MyClass *)ptr;   all over the place, but there seem to be two other types of casts, and I don't know the difference. What's the difference between the following lines of code?  MyClass *m = (MyClass *)ptr; MyClass *m = static_cast&lt;MyClass *&gt;(ptr); MyClass *m = dynamic_cast&lt;MyClass *&gt;(ptr);