I'm changing the default setting for arp_ignore on an ubuntu 16.04 server, from it's default value 0 to 1.  My understanding of the /proc/sys/net/ipv4/conf/ directory is that files under all will affect all interfaces, and default will affect newly created interfaces.  After changing the value of /proc/sys/net/ipv4/conf/all/arp_ignore to 1, the other files are still set to 0:  cat /proc/sys/net/ipv4/conf/*/arp_ignore 1 0 0 0   Does the value of /proc/sys/net/ipv4/conf/all/arp_ignore just override the interface specific files rather than changing their values?
In sysctl, the /proc/sys/net/ipv[46]/conf/ keys have the following subkeys: all, default, and a key for each network interface. For example, on a machine with a single network interface eth0, it will look like this:  iserv ~ # ll /proc/sys/net/ipv[46]/conf/ /proc/sys/net/ipv4/conf/: insgesamt 0 dr-xr-xr-x 0 root root 0 12. Sep 23:30 all/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 default/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 eth0/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 lo/  /proc/sys/net/ipv6/conf/: insgesamt 0 dr-xr-xr-x 0 root root 0 12. Sep 23:30 all/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 default/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 eth0/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 lo/   All the respective settings exist in each key separately. For example, if I want to disable IPv6 Router Advertisements with the accept_ra value, this value exists four times:  iserv ~ # sysctl -a 2&gt;/dev/null | grep "accept_ra " net.ipv6.conf.all.accept_ra = 1 net.ipv6.conf.default.accept_ra = 1 net.ipv6.conf.lo.accept_ra = 1 net.ipv6.conf.eth0.accept_ra = 1   My question now is: which of these values do I need to change? I figured all (to change all existing interfaces) and default (to change all new interfaces that may appear later), but changing these still leaves the value at 1 for lo and eth0:  iserv ~ # sysctl -w net.ipv6.conf.all.accept_ra=0 net.ipv6.conf.all.accept_ra = 0 iserv ~ # sysctl -w net.ipv6.conf.default.accept_ra=0 net.ipv6.conf.default.accept_ra = 0 iserv ~ # sysctl -a 2&gt;/dev/null | grep "accept_ra "   net.ipv6.conf.all.accept_ra = 0 net.ipv6.conf.default.accept_ra = 0 net.ipv6.conf.lo.accept_ra = 1 net.ipv6.conf.eth0.accept_ra = 1   Will the machine now accept Router Advertisements on eth0, or will it not?
This may be a very basic question.      Let $R$ be a commutative ring with unity (may be assumed to be an integral domain, if necessary) and $I$ be an ideal of $R$. Assume that $R/I$ is isomorphic to $R$. Does this mean $I=(0)$ ? When would I need a SecureString in .NET? Total order on complex numbers $X/{\sim}$ is Hausdorff if and only if $\sim$ is closed in $X \times X$ Wrong text instead of reference numbers with the spbasic bibiography style I am writing a paper to a Springer journal and I am trying to use   \bibliographystyle{spbasic} However, instead of the number of the reference in the list of references I get something as:     [Hundsdorfer et al(1995)Hundsdorfer, Koren, van Loon, and Verwer]   followed by the citation  What should I do to get the number in the square brackets?  \documentclass[smallextended]{svjour3} \begin{document} \cite{Hundsdorfer:adv}  \bibliographystyle{spbasic}  \bibliography{moje.bib}   % name your BibTeX data base  \end{document}   I may have to do the bibliography manually, as no Springer provided bibtex style produces the output that can be seen in the journal articles. What's the frequency of filesystem check on boot? What is the maximum number of times the root filesystem on this computer can be mounted before it is automatically checked? When I entered the -al attribute with the  command, I got the following:  anupam@JAZZ:~/blog$ ls -al total 76 drwxrwxr-x 13 anupam anupam 4096 Aug 28 21:45 . drwxr-xr-x 34 anupam anupam 4096 Aug 28 20:52 .. drwxrwxr-x  8 anupam anupam 4096 Aug 28 12:19 app drwxr-xr-x  2 anupam anupam 4096 Aug 28 12:19 bin drwxrwxr-x  5 anupam anupam 4096 Aug 28 12:19 config -rw-rw-r--  1 anupam anupam  154 Aug 28 12:19 config.ru drwxrwxr-x  3 anupam anupam 4096 Aug 28 12:37 db -rw-rw-r--  1 anupam anupam 1339 Aug 28 12:19 Gemfile -rw-rw-r--  1 anupam anupam 2871 Aug 28 12:19 Gemfile.lock drwxrwxr-x  7 anupam anupam 4096 Aug 28 21:45 .git -rw-rw-r--  1 anupam anupam  466 Aug 28 12:19 .gitignore drwxrwxr-x  4 anupam anupam 4096 Aug 28 12:19 lib drwxrwxr-x  2 anupam anupam 4096 Aug 28 12:29 log drwxrwxr-x  2 anupam anupam 4096 Aug 28 12:19 public -rw-rw-r--  1 anupam anupam  249 Aug 28 12:19 Rakefile -rw-rw-r--  1 anupam anupam  478 Aug 28 12:19 README.rdoc drwxrwxr-x  8 anupam anupam 4096 Aug 28 12:19 test drwxrwxr-x  6 anupam anupam 4096 Aug 28 12:33 tmp drwxrwxr-x  3 anupam anupam 4096 Aug 28 12:19 vendor   What does each column mean, and what does the total 76 signify here? The choice of measurement basis on one half of an entangled state affects the other half. Can this be used to communicate faster than light? It is often stated, particularly in popular physics articles and videos, that if one measures a particle A that is entangled with some other particle B, then this measurement will immediately affect the state of the entangled partner.  For example, if Alice and Bob share an entangled pair of electrons and Alice measures her spin in the $x$ direction, then Bob's spin will also end up spinning in that direction, and similarly if she measures in the $z$ direction. Moreover, the effect will be instantaneous, regardless of the spatial distance between the two particles, which seems at odds with special relativity.  Can I use a scheme like this to communicate faster than light? How to illuminate the darkness inside glass objects in Cycles? My model has a clear plastic (or glass) dome with objects inside.  The objects appear dark.  I've tried the glass shader with color 100% RGB, with very small IOR, and using just a refraction shader.    I know Cycles has problems with caustics, but I just want broad illumination to fall clean through the glass.  The light-to-column path can ignore refraction, but is blocked or tremendously attenuated. The camera-column path needs refraction, and seems to work fine anyway.  This demo image offers all optical paths of interest:   light upon object, seen directly light upon object, seen through glass (looks okay) light through glass onto object, seen directly. This is the shadow on the lit side of the column just below the glass tubing.  I expect full illumination, but there is shadow.  There is some light, but it's diffuse light from the floor. light through glass onto object, seen through glass. This     I did at one point try non-progressive rendering, and find extremely coarse light where there shouldn't be shadow, but this is not a practical way to make nice images. I've even tried cranking up certain sampling settings to many thousands, but still get bad noise though less, at the cost of long render times. I  would like to finish my creations sometime before "Star Trek, the Generation After the Next" becomes real life, if you know what I mean.  The next image is an example. I think Transmission in Sampling was 5000, but not sure.    I'm using Cycles in Blender 2.67 on a quad core Linux machine, 16GB RAM. Machine limits have never been a problem for 3D rendering.  Possibly, I screwed up some setting when I made my startup file, and just need to fix it. OTOH maybe this is just a limitation of path tracing, or of the way Cycles does it. If that's the case, what to real-world Blender artists do when they need to produce images on a budget and schedule?  What is the practical real-world fix? Getting the Volume of an Uneven Mesh How do I reset my main keychain and completely delete the old one? I changed my password and its been coming up with all of these popups asking for my new password when I first login. If anyone can help with updating my keychain I would appreciate it or you can just help me completely delete and reset it. When you attempt to modify a file without having write permissions on it, you get an error:  &gt; touch /tmp/foo &amp;&amp; sudo chown root /tmp/foo &gt; echo test &gt; /tmp/foo zsh: permission denied: /tmp/foo   Sudoing doesn't help, because it runs the command as root, but the shell handles redirecting stdout and opens the file as you anyway:  &gt; sudo echo test &gt; /tmp/foo zsh: permission denied: /tmp/foo   Is there an easy way to redirect stdout to a file you don't have permission to write to, besides opening a shell as root and manipulating the file that way?  &gt; sudo su # echo test &gt; /tmp/foo How to lock compiled Java classes to prevent decompilation? How do I lock compiled Java classes to prevent decompilation?  I know this must be very well discussed topic on the Internet, but I could not come to any conclusion after referring them.  Many people do suggest obfuscator, but they just do renaming of classes, methods, and fields with tough-to-remember character sequences but what about sensitive constant values?  For example, you have developed the encryption and decryption component based on a password based encryption technique. Now in this case, any average Java person can use  to decompile the class file and easily retrieve the password value (defined as constant) as well as  and in turn can decrypt the data by writing small independent program!  Or should such sensitive components be built in native code (for example, VC++) and call them via ? Why does friction play the role of centripetal force during the turning of a car? What makes frictional force the centripetal force of a car turning along a curve? As friction is the opposing force and acts anti-parallel so there is no component of frictional force towards the center,right? Then how can frictional force be centripetal force? Proof of Young's inequality The following problem is from Spivak's Calculus.  Suppose that $f$ is a continuous increasing function with $f(0)=0$. Prove that for $a,b \gt 0$ we have Young's inequality   $$ ab \le \int_0^af(x)dx+\int_0^bf^{-1}(x)dx$$, and that equality holds if and only if $b=f(a)$.  It is enough to consider the case $f(a) \gt b$, and show that the strict inequality occurs in this case.  I've tried proving this using the theorem  $$ \int_a^bf^{-1}=bf^{-1}(b)-af^{-1}(a)-\int_{f^{-1}(a)}^{f^{-1}(b)}f$$  but I got stuck along the way.   How may I show this rigorously using the definition or properties of integrals? Any hint, suggestions or solutions would be appreciated. Implementing the decorator pattern in Python Best way to parse command line arguments in C#? When building console applications that take parameters, you can use the arguments passed to Main(string[] args).   In the past I've simply indexed/looped that array and done a few regular expressions to extract the values. However, when the commands get more complicated, the parsing can get pretty ugly.    So I'm interested in:   Libraries that you use Patterns that you use   Assume the commands always adhere to common standards such as . Prove $\limsup\limits_{n \to \infty} (a_n+b_n) \le \limsup\limits_{n \to \infty} a_n + \limsup\limits_{n \to \infty} b_n$ I am stuck with the following problem.     Prove that $$\limsup_{n \to \infty} (a_n+b_n) \le \limsup_{n \to \infty} a_n + \limsup_{n \to \infty} b_n$$   I was thinking of using the triangle inequality saying $$|a_n + b_n| \le |a_n| + |b_n|$$ but the problem is not about absolute values of the sequence.  Intuitively it's clear that this is true because $a_n$ and $b_n$ can "reduce each others magnitude" if they have opposite signs, but I cannot express that algebraically...  Can someone help me out ? Cardinality of the Cartesian Product of Two Equinumerous Infinite Sets Is the cardinality of the Cartesian product of two equinumerous infinite sets the same as the cardinality of any one of the sets? I couldn't find this explicitly stated in any handout or text. This certainly seems to be true from the examples I have seen:  The Cartesian product of two infinitely countable sets is again infinitely countable. The Cartesian product of two sets with cardinality of continuum again has cardinality of continuum. How can I mount the /system directory rewritable or read-only on my Android phone?