After trying to upgrade from 17.04 to 18.0 this message appears:  E: The repository 'http://ppa.launchpad.net/jonathonf/vlc/ubuntu zesty Release' does not have a Release file. W: Updating from such a repository can't be done securely, and is therefore disabled by default. W: See apt-secure(8) manpage for repository creation and user configuration details. W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/sources.list.d/videolan-ubuntu-master-daily-zesty.list:2 and /etc/apt/sources.list.d/videolan-ubuntu-master-daily-zesty.list:3 E: The repository 'http://ppa.launchpad.net/videolan/stable-daily/ubuntu zesty Release' does not have a Release file. W: Updating from such a repository can't be done securely, and is therefore disabled by default. W: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://archive.ubuntu.com/ubuntu zesty Release' does not have a Release file. W: Updating from such a repository can't be done securely, and is therefore disabled by default. W: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://archive.ubuntu.com/ubuntu zesty-updates Release' does not have a Release file.    W: Updating from such a repository can't be done securely, and is therefore disabled by default. W: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://archive.ubuntu.com/ubuntu zesty-backports Release' does not have a Release file.   W: Updating from such a repository can't be done securely, and is therefore disabled by default. W: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://archive.ubuntu.com/ubuntu zesty-security Release' does not have a Release file. W: Updating from such a repository can't be done securely, and is therefore disabled by default. W: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://archive.ubuntu.com/ubuntu zesty-proposed Release' does not have a Release file.  I have a netbook eMachines E350, Intel Atom processor, and 2GB RAM memory. Is it necessary to download the 18.04 ISO image?
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
Getting command-not-found working under zsh Inaccurate altitude GPS data with my Android? How to Disavow Bad Backlinks Automatically? What does the `who` command result `root :0` mean? The return value of command who will always include root :0 in X Window pts. I guess it actually means the GNOME login. Am I right?  Another question is where to get this knowledge, as I don't see it in the man who, neither in info who.  Example  [root@localhost root]# who root     :0           Sep 11 06:33  root     pts/0        Sep 11 06:36     (:0.0) Does a percentage require a singular or plural verb, for example, do we say ten percent "go" or "goes"? Upgrade to version newer than repositories I have  about how to upgrade ghostscript to a version that is available on 15.04 but not on 14.04LTS (which I have). On this site there are numerous almost identical question regarding different packages, a few examples include:         So I thought it would be very useful in general to know: is there  a general, automated way to upgrade a package, including all its dependencies, to a version that is newer than Ubuntu's repos? Is this more easily done if the newer version exists in more recent Ubuntu releases? ReadList can't read from file containing high-precision Reals I am looking for an adjective/noun for someone who is able to speak/ makes speeches very well and uses words effectively to influence/impress people. Evaluation of ratio of two binomial expression How to stop apt from doing anything Harmonic Function with linear growth First I tried to use integration: $$y=\lim_{n\to\infty}\frac{a^n}{n!}=\lim_{n\to\infty}\frac{a}{1}\cdot\frac{a}{2}\cdot\frac{a}{3}\cdots\frac{a}{n}$$ $$\log y=\lim_{n\to\infty}\sum_{r=1}^n\log\frac{a}{r}$$ But I could not express it as a riemann integral. Now I am thinking about sandwich theorem.  $$\frac{a}{n!}=\frac{a}{1}\cdot\frac{a}{2}\cdot\frac{a}{3}\cdots\frac{a}{t} \cdot\frac{a}{t+1}\cdot\frac{a}{t+2}\cdots\frac{a}{n}=\frac{a}{t!}\cdot\frac{a}{t+1}\cdot\frac{a}{t+2}\cdots\frac{a}{n}$$ Since $\frac{a}{t+1}&gt;\frac{a}{t+2}&gt;\frac{a}{t+1}&gt;\cdots&gt;\frac{a}{n}$ $$\frac{a^n}{n!}&lt;\frac{a^t}{t!}\cdot\big(\frac{a}{t+1}\big)^{n-t}$$ since $\frac{a}{t+1}&lt;1$, $$\lim_{n\to\infty}\big(\frac{a}{t+1}\big)^{n-t}=0$$ Hence, $$\lim_{n\to\infty}\frac{a^t}{t!}\big(\frac{a}{t+1}\big)^{n-t}=0$$ And by using sandwich theorem, $y=0$. Is this correct? Functional equation $f(r \cos \varphi)+f(r \sin \varphi)=f(r)$ Find all such monotonous function $f:[0,+\infty)\to \mathbb R$, such that for any real $r\ge0$ and $\varphi \in \left[\frac{\pi}6, \frac{\pi}4\right]$, $$f(r \cos \varphi)+f(r \sin \varphi)=f(r)\text.$$  My work so far:  If $\varphi \in \left[\frac{\pi}6, \frac{\pi}4\right]$ then $$\frac{\sqrt2}2\le\cos \varphi\le\frac{\sqrt3}2$$ $$\frac12\le\sin \varphi\le\frac{\sqrt2}2$$  If $r=0$ then $f(0)=0$  If $\varphi= \frac{\pi}{4}$ then $$f(r)=4f\left(\frac r2\right)$$  $f(x)=cx^2$ for $x\ge0$ and $c\in\mathbb R$ I am using a mirror modifier for modelling. When viewing the mesh in edit mode, the vertices in the center are firmly stuck together and cannot be separated.     When in pose mode, I manipulate a wrist bone on my model and the mesh splits in two along the mirror axis center.    I have tried removing the subsurface modifier to see if this was the problem leaving only the armature at the top of the modifier list,i.e. as first modifier (which I am told is the bottom of the stack) and the mirror as the second.  It doesn't separate in edit mode and I've also tried increasing the merge limit to 0.1 and there's no change. Manipulating bones separates the mesh. Evaluate the integral: $\int_{0}^{1} \frac{\ln(x+1)}{x^2+1} \mathrm dx$ Looking for a science fiction story collection about nanotechnology — included a story about anti-graffiti paint I remember reading it while in middle school in English in the United States, so the latest it would have come out was 1998. I don't remember if it was all one author, or even the same universe. These are the stories I remember:   A man finds a way to create a medicine that prevents radiation poisoning (or possibly makes someone fireproof... it's a little confused in my head) and learns that part of the problem is finding a market for it. I vividly remember the inventor telling someone to not "let the doorknob ream you" as it slams shut. A bout of graffiti artists leads to the city buying anti-graffiti paint that dissolves any other paint put on top of it. After learning the futility of trying to paint over it, the protagonist consults with a friend and learns that the anti-graffiti paint will eat away at the paint above it at a steady rate, and will even eat successive layers of the anti-graffiti paint. he uses this property to engineer an animation involving a harlequin thumbing this nose at the officials even as they try to wash it away. Some guys (I want to say a gang) go to a clinic for an illegal nanotech transformation. The viewpoint character gets turned into a woman while a friend gets turned into a dog. After roaming about in their new forms, they return to find the clinic being raided, meaning there's no one to turn them back. I think I remember something bad happening to the one transformed into a dog where the transformation continued, erasing his human thought patterns. There was also a scene where the viewpoint character submitted to being sexually assaulted by his former friends as if it was simply to be expected given his form.   I don't remember if the first or the second story was the actual first story of the collection... I want to say that those are the order that they showed up as in the book. I'm having a problem rendering the environment map. I downloaded a sample project that has the same settings as my project but it renders without a problem. I tried using both a .hdr and .png image. Attached are screenshots with node settings. First is the incorrect render and 2nd image is the project the renders correctly. How do I go about fixing this? Deleting multiple elements from a list Let $a$ be a non-zero real number. Is it true that the value of $$\int\limits_0^\infty \frac{\mathrm{d} x}{(1+x^2)(1+x^a)}$$  is independent on $a$? Background image shows in front of 3D objects, not behind them. I've done a quick 3D track in blender and I'm trying to render my output, but the plate I used to track is showing up over my 3d objects.  I want to render the objects in the scene with an alpha channel and comp them over the plate I tracked. My renders however, are covered by the aforementioned plate.  Un-checking "Background Images" in the camera properties (only removes it from the viewport) isn't doing it for my render outputs.  Working on some production tests and am not really proficient with the software yet, my apologies in advance.