I'm new to Ubuntu and Linux in general and coming from Windows I was wondering how to upgrade Ubuntu from one version to another. A new version is released each six months, right? So let's say I'm now running 13.04. When 13.10 will be released in october, how will I upgrade my system?  Will I have to reinstall my whole Linux, loosing all my programs or is there a way to simply replace 13.04 by 13.10?
How can I safely upgrade an Ubuntu installation from one release to another? What should I do before upgrading to ensure it goes smoothly, and is there any clean-up I need to do afterwards?  In particular, do I need to do anything special if I am using packages from PPAs, if I have a graphics card that needs drivers, or if I'm running a custom Linux kernel?  This is a general question , but as example we take Ubuntu 12.04 and Ubuntu 12.10
Why does my regular expression work in X but not in Y? I wrote a regular expression which works well in a certain program (grep, sed, awk, perl, python, ruby, ksh, bash, zsh, find, emacs, vi, vim, gedit, …). But when I use it in a different program (or on a different unix variant), it stops matching. Why? The internals of bcrypt I'm attempting to get a better understanding of cryptography and have run into some questions about bcrypt.   Bcrypt relies on the blowfish cipher, which is a reversible method of encryption. But bcrypt is not reversible. How is that possible? Or am I mistaken? What does bcrypt do on top of blowfish to make it irreversible? Why does bcrypt use blowfish instead of twofish or threefish? How to generate the random default "gravatars" like on Stack Overflow? How does Stack Overflow auto-generate the gravatars for those users who do not upload a picture or who have not created a Gravatar icon?    Where do these random avatars come from, and how can I generate them for my own site? Visual Studio Editor does not underline errors anymore My Visual Studio (2008) Editor has stopped to underline Errors (this nifty wavy red lines). I can't really tell when, but it can be related to the installation of .Net Framework 3.5 SP 1 or the MVC Beta (which I guess is unlikely). Furthermore have I installed and uninstalled both CodeRush and Resharper for evaluation purposes (decided not to keep either one of them).  Does anyone know the problem and how to restore this functionality again? How to clear Chocolatey cache in the free version? Installation-file-cleaning is currently only available in  () and .  The package installation files can easily take gigabytes of storage space and to my knowledge they only increase in size as the user updates packages and installs new software, with only your hard drive capacity as the upper limit.   I don't know if Chocolatey stores cache in one central location — something is saved to ~\AppData\Local\Temp but the majority is located in the lib* folders in ~\ProgramData\chocolatey. Also the log files in the logs folder total to over 100 MB on my system. Is there any way to fully clear Chocolatey cache without manually deleting directories? Show that $ \sum_{n=2}^m \binom{n}{2} = \binom{m+1}{3}$ I need a hand in showing that $$ \sum_{n=2}^m \binom{n}{2} = \binom{m+1}{3}$$   Thanks in advance for any help. Using the validation data I'm unclear on the exact process of using the validation data.  Let's say that I fit my neural network model and adjust hyperparameters using the training set and validation set. Do I then evaluate the test set on this model? Or do I recombine the validation and training sets and fit a fresh model with the hyperparameters that I found during the validation phase, and then evaluate on the test data? I have seen a number of different notebooks and examples that do both ways.  Surely, once I've found my hyperparameters, it makes sense to fit a fresh model using the full training set (recombined with validation set), since the validation loss has no effect on the weights. If electrons were positive and protons were negative, would life be different? Is there an official rule that the minimum damage can't be negative? Which is the right way to do something like 'description' list but with customizable and fixed-width labels? I.e. something like this:  Label:         Text text text text text text                text text text text. Longer label:  Text text text text text text                Text text text text.   The way I see it to use two-column table (first columt for labels and second column for descriptions), but this solution seems ugly. Is there any other way? Escaped line break tag in tooltip on election page How can I reuse existing materials, objects, etc from an existing .blend? I have created several designs for a particular project and they are related, but I don't want to have to keep recreating any similar elements, such as shared materials or textures.  How can I use the existing data in a new Blender file? what does the ldapadd error: "additional info: objectClass: value #2invalid per syntax mean? Let $(a_n)_{n}\in\ell^2:=\ell^2(\mathbb{R})$ be a fixed sequence. Consider the subspace $$C=\{(x_n)_{n}\in\ell^2 : |x_n|\le a_n\text{ for all }n\in\mathbb{N}\}.$$  According to the book [Dunford and Schwartz, Linear operators part I, page 453] $C$ is compact in the $\ell^2$-norm, but there is no proof. How can I show that $C$ is indeed compact in $\ell^2$ ? SF TV show about a war between humans and aliens? "One of the children who was" vs. "one of the children who were" In the construction "one of the [plural noun] who ...", should the verb agree with "one" or "[plural noun]"?   For example, which of the two following sentences is grammatically correct? Or are both acceptable?        She was one of the several children who was sold at the auction    She was one of the several children who were sold at the auction. Momentum is defined by the product of mass and velocity. Now a projectile out of a gun has to have high velocity to penetrate a human body, as its mass isn't significant. But to reach this velocity, due to inertia/the law of energy conservation, momentum on both sides is to be equal. As there is strong negative acceleration in the opposite direction of the bullet, it should result in a strong force in the opposite direction of the bullet ($F = m*a $).  Therefore I wonder why shooting a bullet with a handgun is not ripping your hand apart. Producing PDF/X compliant document with XeLaTeX Proof of "the continuous image of a connected set is connected" None of the existing questions is exactly answering my question so I'm posting a new question, but feel free to refer me to some already answered question!   In Rudin Theorem 4.22, we know that      If $f$ is a continuous mapping of a metric space $X$ into a metric space $Y$, and $E$ is a connected subset of $X$, then $f(E)$ is connected.    In the proof, we started with consider $f(E) = A \cup B$, where $A$ and $B$ are nonempty separated subsets. Then put $G = E \cap f^{-1}(A)$ and $H = E \cap f^{-1}(B)$. Then Rudin is claiming that $E = G \cup H$. I'm a little suspicious about this. What if $f$ is non-surjective, then $f^{-1}(A) \cup f^{-1}(B)$  is only a proper subset of $E$? Is there a property of $f$ being continuous that forces $f$ to be 1-1? Is there to make the login screen appear on the external display in 18.04?