Cardinality of the union of an ascending chain of sets
Cardinality of a totally ordered union
How to connect to my web server? I have implemented a simple web server as a solution to a course assignment and I want to connect to this web server over the internet. I've set it up to listen on port 22881 and configured my router accordingly as the screenshot below shows    I'm able to connect to my web server locally using http://localhost:22881 and I can connect to the router's interface when I visit http://my.external.ip, but I can't connect to my web server using http://my.external.ip:22881 (I get a connection timeout). Any idea of what may be the problem?  Thanks in advance! Network interface name changes after update to 15.10 - udev changes I updated a virtual machine running Ubuntu server 15.04 to the just released new stable 15.10.  There were no apparent problems, but after reboot the machine lost its network connection. lspci showed the correct card and lsmod proved that the driver had been loaded.  Hints about editing or removing /etc/udev/rules.d/70-persistent-net.rules did not succeed (still no network, no new file), the famous /lib/udev/write_net_rules did not even exist.  I don't have much clue regarding udev and systemd, so it took me some time to find in /sys/class/net that the network interface name changed. It became ens32, which was renamed from eth0. After I changed /etc/network/interfaces network communication was enabled again.  But - why does this happen at all? And if it happens, shouldn't the interfaces file be updated automatically?  Now that I deleted the virtual network card and created another one, eth0 becomes eno16777728, which is not so, uhm, nice.  Should this behaviour (at least that of the upgrade procedure) be reported as a bug?  Furthermore, is /etc/udev/rules.d/70-persistent-net.rules obsolete now? And (although only partly related) what about /etc/udev/rules.d/70-persistent-cd.rules?)  Edit - additional question (after accepted answer) The dependency of /etc/network/interfaces from the actual interface name bothered me. I tried a new installation of *ubuntu in another virtual machine. To my surprise, /etc/network/interfaces contained a reference to the loopback device only. However, with my original VM this change prevented the network to come up. So what else do I need to change?  Edit Well, from another test I found that a new Ubuntu Server has the network interface card in /etc/network/interfaces, while XUbuntu has not. Maybe it is using network-manager or something else. Does separation of variables in PDEs give a general solution? When a partial differential equation is solved using the separation of variables method, is the produced solution the most general one that satisfies the equation or have we lost some forms of the solution because of the assumption that it is in the form of separated variables? Is my paper under review (or similar) for too long and if yes, how should I react? How to connect to Android through SSH over 3G/4G public IP? How is the value of $\pi$ ( Pi ) actually calculated? When I was a child I was taught $\pi$ (Circumference/Diameter) is an irrational number  and can be approximated to $22/7$ but $= 3.(142857)(\ldots)$.      But where does this value comes from?  In short How do I derive $\pi$? String concatenation: concat() vs "+" operator How do I craft command blocks? I went to my friends house, and he was playing Minecraft on the PC. He showed me a command block, but when I went home and opened Minecraft pocket edition, I went to the crafting table but I could not find any command blocks to craft.  What are command blocks and how do I craft them? How to disable the "Get Windows 10" icon shown in the notification area (tray)? This icon showed up in my taskbar notification area today and I cannot seem to get rid of it:    Clicking on it displays the following screen:    So how do I disable or remove the "Get Windows 10" icon? We have the matrix: $$\left[\begin{array}{rrr} 0.8&amp;0&amp;0\\ 0&amp;1.2&amp;0\\ 0&amp;0&amp;1\\\end{array}\right]$$ Finding the eigenvalues and eigenvectors are easy. But finding ${\bf M}^n$ when $n \rightarrow \infty$ is the hard part. Any suggestions? My problem is that I have only one reference. So I would like the head of this part to appear "Reference" instead of commonly "References". More generally, could we change the title "References" to an arbitrary name?  Thank you very much for your help! I'm making all my diagrams in SVG format using Inkscape and then I export them to some other format (e.g. PDF, EPS or PNG). I wrote a short script that does this for me automatically, but I'd like to avoid this step, if possible --- sometimes the conversion from SVG converts the text labels into vectors, and that's annoying. Hence the question:  Is there a way to include SVG diagrams directly without conversion to an intermediate format?  Package suggestions, or instructions for specific LaTeX distribution are welcome. Tips and personal experience on which tools you have found to be working reliably would be also appreciated. Extracting numbers from string field using Python Parser of ArcMap Field Calculator? I am trying to calculate field test2 with only the numeric values from a string field test. The entire script is like:    def makestr(test)      list=[]      for s in test:          if s.isdigit():              list.append(s)      for a in list:          str=''.join(list)     But I keep getting an error:    Any ideas? "Dummy Output" No sound in Ubuntu 16.04 None of the HDMI output are working, all saying "dummy output", it was working yesterday, but when I use the headphones it became soundless, with or without the headphones.  Thank you already! Word for someone that always has to be right Is there a word for someone that always has to be right? The person gets angry if they are not. Is it possible to log back into a Pokemon Go account? What's a quick way of copying the path to the directory that's currently open in Finder?   Copying that path is very easy in Linux and Windows file managers - you just need to copy it from the address bar. I don't see a corresponding option in Finder. How to install Hp laser jet 1020 plus printer? So I watched the following .  In the clip, using what seems to be the recording from a standard bank camera, they zoom in at least 100, and see the image of the culprit in the reflection of the eye of the girl.  Now, I thought this was completely ridiculous, so much so that I thought it was actually really funny.    However, my friend argued that there are very good tricks for image enhancement, such as "super resolution" a procedure where multiple frames of a video to produce a much higher single resolution image.   He did think the show bends the truth quite a bit, but how much?  Honestly, I don't actually know anything about these things, so my question is:     How good is modern image resolution enhancement?  Also, how far off are the CSI television programs?    Thank you,  Remark: This is  on the Skeptics site.  I was told I might receive better answers here. Will my device work with Ubuntu?