I have Ubuntu 19.10 (GNU/Linux 5.3.0-1030-raspi2 aarch64). ubuntu@ubuntu:~$ do-release-upgrade Checking for a new Ubuntu release Your Ubuntu release is not supported anymore. For upgrade information, please visit: http://www.ubuntu.com/releaseendoflife  Please install all available updates for your release before upgrading.  But as it tries to do an update: ubuntu@ubuntu:~$ sudo apt update ... E: The repository 'http://ports.ubuntu.com/ubuntu-ports eoan Release' no longer has a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://ports.ubuntu.com/ubuntu-ports eoan-updates Release' no longer has a Release file. ...  I can't install any package either. What is the way to upgrade?
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
The tutorial I read is based on 2.79. So I'm not sure if it's still the same name in 2.8. But I can't find anything providing similar functionalities. Converting the beta coefficient from matrix to scalar notation in OLS regression Concave implies subadditive "Startup Applications" not working Obtaining remote host name in bash script Sorry my knowledge of Linux bash commands is pretty basic, I've been searching for a while but I'm not 100% sure what I need to search for.  I was wondering if there's a way to grab the current logged in users remote host name in a Linux bash script? I have a script in which I need to log each time a user runs it. I'm obtaining the date like so:  cdat=`/bin/date +%a' '%d' '%h' '%Y', '%H':'%M`;   I now need to add the users remote host (not the username they logged in with). I'm not 100% sure I'm using the right terminology here either, just to clarify; by 'remote host name' I mean the same output that prints on the screen on most servers I've logged into over ssh, for example:  Last login: Mon Jul 22 16:35:09 2013 from win7-i7-stuart.my.domain.com   I'm looking for the win7-i7-stuart.my.domain.com bit. What's the difference between the list methods append() and extend()? How would I implement a binary search using just an array? ꕺ (U+A57A Vai Syllable Kpoo) is allowed in character names as the last character I believe this should be changed so ꕺ can not be the last character of a name at minimum. This could be a bug in my opinion because it provides confusion with diamond mods.  Although other symbols are blocked from what I understand but this does technically look different.  I have changed my name to such to demonstrate the confusion at least temporarily.  They say imitation is the greatest form of flattery so maybe this should be accepted because to anyone who is familiar with SO I doubt this would cause an issue. Strange behavior of $\lim_{x\to0}\frac{\sin\left(x\sin\left(\frac1x\right)\right)}{x\sin\left(\frac1x\right)}$ Alright, scratch everything below the line. Let me present one cohesive question not marred by repeated edits.  The limit $\lim_{x\to a}f(x)=L$ exists iff for every $\epsilon&gt;0$ there is a $\delta&gt;0$ such that $|f(x)-L|&lt;\epsilon$ when $0&lt;|x-a|&lt;\delta$.  Thus, $\lim_{x\to0}\sin\left(\frac1x\right)$ does not exist because, being that it oscillates infinitely near $0$, there is no $\epsilon,\delta$.  On the other hand, with the limit$$\lim_{x\to0}\frac{\sin\left(x\sin\left(\frac1x\right)\right)}{x\sin\left(\frac1x\right)}\\\lim_{x\to0}x\sin\left(\frac1x\right)=0\\y=x\sin\left(\frac1x\right)\\\lim_{y\to0}\frac{\sin y}{y}=1\\\lim_{x\to0}\frac{\sin\left(x\sin\left(\frac1x\right)\right)}{x\sin\left(\frac1x\right)}=1$$  this proof can be shown. However, since $\sin\left(\frac1x\right)$ oscillates infinitely, by the same definition of limit we used to show the above, the limit does not exist. How do I resolve this discrepancy? How to disable Chrome's Incognito Mode? Reward for Passing Review tests? Just wanted to see what the community thought of adding a reward to passing the review tests? Maybe a 1 point reward?  I know seeing the tests in the review area has helped me be extra careful when reviewing, but I thought perhaps a little boost in incentive would be cool. Prevent execution of parent event handler Get selected text from a drop-down list (select box) using jQuery Do superheroes/villains like Quicksilver or Flash with super speed get tired due to running? Programmatically obtaining Big-O efficiency of code I wonder whether there is any automatic way of determining (at least roughly) the Big-O time complexity of a given function?  If I graphed an O(n) function vs. an O(n lg n) function I think I would be able to visually ascertain which is which; I'm thinking there must be some heuristic solution which enables this to be done automatically.  Any ideas?  Edit: I am happy to find a semi-automated solution, just wondering whether there is some way of avoiding doing a fully manual analysis. Area of intersection between two circles Suppose you have 2 circles that intersect each other in such a way that each circle passes through the other's center. What is the area between the circle(or common area) i.e. area between the centres of the circles? Why do gaps appear in my mesh when I animate it? As I attempt to complete a "Walk cycle" with my model, the mesh at the pants line separates from the skin as the model moves or as I rotate the controls. This happens in many places on my model and it reveals the model interior. It is a one piece mesh, though, so I don't understand why this happens. Is this caused by weight painting problems? How can I fix this? Java Hashmap: How to get key from value? When testing the following code:  from osgeo import gdal import json   def read_file(filename):     f = gdal.VSIFOpenL(filename, "rb")     if f is None:         return None     content = gdal.VSIFReadL(1, 10000, f).decode('UTF-8')     gdal.VSIFCloseL(f)     return content   gdal.VectorTranslate('out.json', """{   "type": "FeatureCollection",   "features": [       { "type": "Feature", "geometry": { "type": "Polygon", "coordinates": "coordinates":[[[-188.56933593749997,61.58549218152362],[-173.9794921875,61.58549218152362],[-173.9794921875,66.00015035652659],[-188.56933593749997,66.00015035652659],[-188.56933593749997,61.58549218152362]]] } },   ] }""", format = 'GeoJSON', layerCreationOptions = ['RFC7946=YES', 'WRITE_BBOX=YES'])  got = read_file('/vsimem/out.json') gdal.Unlink('/vsimem/out.json')  print json.loads(got)   from this , the file out.json is empty. The folder is with all permissions for writing allowed. When testing the method gdal.OpenEx, is possible to load an object, but still the method gdal.VectorTranslate returns an empty geojson when trying to pass this new loaded object as a srcDS object. Any hint on solving this issue? Why does my dock keep moving back to my other monitor? I have a larger, external monitor connected to my MacBook Pro and have arranged it such that the dock is in the external monitor (via System Preferences > Displays > Arrangement, by dragging the white bar to the larger screen). This works fine, except for the fact that every now and then, the dock will suddenly shift back to my MacBook screen, but when I open up Displays to change this back, the white bar is still on the external monitor. So I have to drag it to the smaller screen, and then drag it back to the external monitor.   It's a minor issue, obviously, but I've noticed that it has been happening more and more frequently and it's getting quite annoying. Perhaps there's something I've been doing unintentionally for this to happen?   I'm using Mavericks, 10.9.5.