Livepatch not updating kernel from 5.4.0.29 to 5.4.0.31
canonical-livepatch, Doesn't seem to patch anything
"Arnold raced out of the door": grammatical or not? Ignore .DS_Store and Icon files in a folder with Cocoa NSFIleManager I really hope someone will take a quick look at the following, I would just love to better understand it...  This exercise is from Arnold's "Mathematical Methods of Classical Mechanics", p. 97 in the chapter on d'Alemberts principle:  A rod of weight P, tilted at an angle of 60° to the plane of a table, begins to fall with initial velocity zero. Find the constraint force of the table at the initial moment, considering the table as  (a) absolutely smooth  (b) absolutely rough  (In the first case, the holonomic constraint holds the end of the rod on the plane of the table, and in the second case, at a given point.)"      I must admit, I am pretty unsure on how to do calculations using this "fancy" mathematical kind of physics.  First off, I'm lost with (a). But I'll have a go at (b): As far as I understood, d'Alemberts principle states, that if $M$ is a constraining manifold, $x(q)$ is a curve in $M$ and $\xi$ is a vector perpendicular to $T_xM$, then $x$ satisfies Lagrange's equations  $\frac{d}{dt} \frac{\partial L}{\partial \dot q} = \frac{\partial L}{\partial q} \qquad L = \frac{{\dot x}^2}{2} - U(x)$  iff for the following inner product, we have  $\left(m \ddot x + \frac{\partial U}{\partial x}, \xi \right) = 0$  I guess that's about right so far? The constraint would in this case essentially be $\mathbb S^1$, since the rod moves on a circe around the point in contact with the table. Can we assume that all the rod's mass is at the center of mass?  Would we then have $U(x) = -gx_2$ in this case (where $x_2$ is the vertical component of $x$)?  If yes, then $\partial U / \partial x = -ge_2$. Where $e_1, e_2$ are the horizontal and vertical unit vectors, respectively.  At the inital moment, we have $x = \cos(60°) e_1 + \sin(60°) e_2$, so by d'Alembert's principle we must have  $\left(m \ddot x + \frac{\partial U}{\partial x}, \cos(60°) e_1 + \sin(60°) e_2 \right) = 0$  or written differently  $m \ddot {x_1} \cos(60°) + m \ddot{x_2} \sin(60°) - \sin(60°)g = 0$    So: Is this correct so far? Or am I way off? Is (a) handled any differently up to this point?  Thanks for reading (and hopefully thanks for your helpful reply)!  If anyone could recommend a good problem book (with solutions), in which this kind of mathematical approach is used (I don't know if this is how physicists would actually compute stuff??), I would greatly appreciate it.  Kind regards,  Sam Galois extension is (not) transitive Let $ K/ L /F $ be fields. If $K / L$ is Galois and $ L / F $ is Galois, then $ K / F$ is Galois. We mentioned this very quickly in today's class without justifying. But I have trouble seeing this. Any help is appreciated.  Our definition for $ K / F$ being Galois is the $F$-automorphism group $G = G( K / F) : = \{ \sigma \in aut (G) : \sigma_F = id_F \}$ fixes only $F$, i.e. $ \{ x \in K : \sigma (x) = x \text { for all } \sigma \in G  \} = F$.  But we also showed that $ K /F$ is Galois if and only if $ K/F$ is normal and separable. I'm a first time Linux user. My laptop wasn't connecting to the wifi so I followed the instructions from .  On typing sudo apt-get update after that, I got this error:  E: Type 'sudo' is not known on line 2 in source list /etc/apt/sources.list E: The list of sources could not be read.   What can I do? Proper way to exit iPhone application? I am programming an iPhone app, and I need to force it to exit due to certain user actions.  After cleaning up memory the app allocated, what's the appropriate method to call to terminate the application? Background  My Lenovo X250 is arriving in two weeks, which according to  will work well only with "a special image of Ubuntu pre-installed by the manufacturer."   points out that the X250 has "Excellent" compatibility to the Linux OSes they install. On the other hand, a quick search on  or  shows that a standard image of Ubuntu on the X250 is rife with hardware problems.  Ubuntu Certified Hardware acknowledges this for the X250: "Standard images of Ubuntu may not work at all on the system or may not work well." This  clearly shows the difference between an Ubuntu standard image installation and the one that comes pre-installed by the manufacturer. Hardware seems to work fully on the OEM version.  Question  Any idea where we may access or download these "special images of Ubuntu"?  (Hopefully not only for the X250, but also for the other systems out there.) How to perfectly align UV coordinates automatically? I have this setup:   The mesh is only the visible top side, with a mirror modifier for the bottom part. Now I want to unwrap it like in the picture. I want the inner circle (red) to go to the top of the UV map...  The problem is that no matter what automatic unwrapping I use, it never works as intended.  The closest I've gotten was by using "follow quads", but that skewed the UV map a lot:   I used the result from the second image and manually adjusted the vertices with a lot of scaling and "align auto", but its very far from perfect as you can see in the first image.  Here's what I want exactly:   The uv vertices should be distributed evenly (horizontally) The middle line (yellow) should be on a "natural" y height (so there's no stretching)   I hope it's clear what I want to achieve. I'm sure there must be some automatic way to perfectly align and distribute the UVs in this way.  By the way: If you look closely you can see that I already placed a uv seam (aligned with the green y axis in the screenshot) but that didn't really help. I have used the websites of SO a lot the past few months because I am busy with a large scale web project. I feel I get better answers here on SO than when I just do a Google search, maybe because I can be more specific here with my problem, and the responses are really fast.  Occasionally when I am not working I try to answer some questions, but the question almost always has an answer which is 'as good as' or 'better' than the answer I would supply.  So my question/answer ratio is about 20/1 something, if not more. When I look at my profile page I see a bucket-load of questions and almost nothing I answered myself.  Is this considered bad behaviour? I can see that this looks a little egoistic.  : One devoted to one's own interests and advancement. I used following command for port scanning of my machine  nc -zv 192.168.1.1 1-100  but I want to filter only succeeded message from  following output.Hence i used the following command   nc -zv 192.168.1.1 1-100|grep succeeded   But no use, still it shows full output   nc: connect to 192.168.1.1 port 1 (tcp) failed: Connection refused nc: connect to 192.168.1.1 port 2 (tcp) failed: Connection refused nc: connect to 192.168.1.1 port 3 (tcp) failed: Connection refused nc: connect to 192.168.1.1 port 4 (tcp) failed: Connection refused nc: connect to 192.168.1.1 port 5 (tcp) failed: Connection refused nc: connect to 192.168.1.1 port 6 (tcp) failed: Connection refused nc: connect to 192.168.1.1 port 7 (tcp) failed: Connection refused nc: connect to 192.168.1.1 port 8 (tcp) failed: Connection refused nc: connect to 192.168.1.1 port 9 (tcp) failed: Connection refused To show that $\sum a_nb_n$ is absolutely convergent Why do we multiply the magnetic flux by the winding number? Is there a way to see questions with a certain tag from all Stack Exchange sites? For example, I see there are questions with the  tag on Stack Overflow, but there are also such questions on Super User, Unix/Linux, and other sites in the network.  Is there a way to follow a tag across all of the Stack Exchange sites, so that one can see the global activity of a topic without visiting all the sites separately? Why is a home fiber connection asymmetric? I recently switched from an ADSL to a fiber connection and was surprised to see that the bandwidth is asymmetric (1 Gbps down / 250 Mbps up).  While this is understandable in ADSL, I do not understand why fiber at home is asymmetric as well? It is not a limitation of the technology (I have symmetric fiber at the office, and always had) How to change Facebook username? How to prove $\gcd(a^2,b^2) = (\gcd(a,b))^2$? How to prove $\gcd(a^2, b^2) = (\gcd(a, b))^2$?  My attempt:  Let $\gcd(a, b) = d$.  Then $d|a$ and $d|b$ then $d^2|a^2$ and $d^2|b^2$. i.e $d^2$ divides $a^2 ~~\&amp;~~ b^2$. Long sites break the layout on the front page The long name pushes the stats to a weird place. And what's with the "Stack Exchange" at the end anyway? If n is such that every element $(\mathbb{Z}/n\mathbb{Z})^{\times}$ is a root of $x^2-1$. Prove that $n$ divides 24. I have a hard time formulating proofs.  For this problem, I  can see that if $n$ is equal to $8,$ this statement is true.  $(\mathbb{Z}/8\mathbb{Z})^{\times}$ includes elements:  $1,3,5,7$, and all of these are roots of $1-x^2 \pmod 8.$  And obviously $8$ divides $24.$  But how do I prove this without depending on number calculations and only using theorems?  Help Please?  I need a step by step walk through of how to do this proof and what theorems would be appropriate to use. Track next Socratic badge progress Just got the  on StackOverflow and, since it can be awarded multiple times, wanted to start tracking progress to the next one, but, the badge is not shown in Available badges to track anymore:    Is it possible to track already awarded badges that can be awarded multiple times? Let $X$ be an infinite cofinite space and let $A \subset X$ be infinite. Then $\overline A = X$  I am having a tough time in trying to understand this. Why is every infinite set in an infinite cofinite space dense ?