I downloaded Xubuntu debian OS when I got my Lenovo laptop many years ago by booting from a USB and following a tutorial. Throughout the years I've wrecked my OS from my ignorance in deleting files that programs like ClamTK flagged as viruses and malware. A bunch of little things malfunction like volume controls, I can't send files to the Recycling Bin via the dropdown menus, I can't view files to upload from my desktop, etc...  I'm wondering how I can remove Windows 10 altogether, then USB boot a regular non-debian Ubuntu (which I think is more accessible for my knowledge of computers and interface friendly) without bricking my laptop. Any help/advice is greatly appreciated.
I would like to see a full how-to guide on how to install Ubuntu.
Why is this trigger finding a null value despite the field being populated? "Seen" status is earlier than the user's last post I posted what I think is a clever answer to:    But then I noticed the question was posted a while ago on Mar 2.  I wanted to see what the chance of the user logging back in and seeing my answer, but the  says the user was seen on Feb 19.  I thought this was supposed to be the date they last logged in? How could they have asked a question on Mar 2 if they haven't logged in since February?  Thanks Is it possible to detect a virus with taskmanager? If I would have a running virus on my system, would I be able to see the process in taskmanager? I mean, would it be possible for a running virus to circumvent the taskmanager so the process doesn't appear in the tasklist of windows7?  Or in other words. If I really now all the processes in taskmanager to be secure, I also know that my PC is clean? How can I make Firefox download different file types to different locations? 98% of what I download is music, so I set the download location to my music folder. However, the other 2% has no place there, so every time I download .doc files or PDF files I have to remove them. Is there a way to make Firefox change the download folder based on file extension? I'll settle for all non-MP3 files getting saved to the desktop.  I know I can right click, choose Save Link As and pick the download location myself, but it seems like there should be a better way. Evaluate forecasting ability of GARCH models with RMSE and MAE This is problem 3.18 from Patrick Morandi's Field and Galois Theory.     Give an example of fields $k \subseteq K \subseteq L$ and $l \subseteq L$ for which $l/k$ and $L/K$ are algebraic, $k$ is algebraically closed in $K$, and $lK = L$, but $l$ is not algebraically closed in $L$.   This question has been asked twice, namely  and , though neither had any answers, and only some inconclusive comments. Normally I wouldn't ask the question again, but after struggling with it for weeks at this point, I emailed Morandi, and he gave me some hints.  He told me that he remembers finding an example, but that he isn't sure. He told me that it would need to be over characteristic $p$ and that the extensions (at least some of them I suppose) could not be separable. Moreover, he told me that $K = k(x)(a)$, where $a$ is a root of an irreducible polynomial $f(x,y) \in k(x,y)$ (I'm not 100% what the root of a two variable polynomial is). Finally, he said that $l$ is an algebraic extension of $k$, where $f$ becomes reducible over $l$. Still however, I can't come up with anything. I was hoping that with these extra hints, someone would be able to figure it out.  He did point out that there is a chance that there is an error in the question, but I haven't managed to prove that such an example cannot exist. Is a strong background in maths a total requisite for ML? I'm starting to want to advance my own skillset and I've always been fascinated by machine learning. However, six years ago instead of pursuing this I decided to take a completely unrelated degree to computer science.   I have been developing software and applications for about 8-10 years now, so I have a good handle but I just can't seem to penetrate the maths side of machine learning/probabilities/statistics.   I start looking at learning material and on the first page it might include something which confuses me and immediately sets up a barrier in my learning.   Is a strong background in maths a total requisite for ML? Should I try and fill in the blanks of my maths before continuing with ML? Can self learning really work for just a developer without any hard computer science background?    Related question: If I create a file and then change its permissions to 444 (read-only), how come rm can remove it?  If I do this:  echo test &gt; test.txt chmod 444 test.txt rm test.txt   ...rm will ask if I want to remove the write-protected file test.txt. I would have expected that rm can not remove such a file and that I would have to do a chmod +w test.txt first. If I do rm -f test.txt then rm will remove the file without even asking, even though it's read-only.   Can anyone clarify? I'm using Ubuntu 12.04/bash. Proof of properties of injective and surjective functions. I'd like to see if these proofs are correct/have them critiqued.     Let $g: A \to B$ and $f: B \to C$ be functions.  Then:   (a) If $g$ and $f$ are one-to-one, then $f \circ g$ is one-to-one.   (b) If $g$ and $f$ are onto, then $f \circ g$ is onto.   (c) If $f \circ g$ is one-to-one, then $f$ is one-to-one?   (d) If $f \circ g$ is one-to-one, then $g$ is one-to-one?   (e) If $f \circ g$ is onto, then $f$ is onto?   (f) If $f \circ g$ is onto, then $g$ is onto?     (a)  Let $a,b \in A$.  If $(f \circ g)(a)=(f \circ g)(b)$, then $f(g(a))=f(g(b))$.  Since $f$ is one-to-one, we know that $g(a)=g(b)$.  And, since $g$ is one-to-one is must be that $a=b$.  Hence $f \circ g$ is one-to-one.    (b) Since $f$ is surjective we know that for all $c \in C$ there is a $b\in B$ such that $f(b)=c$.  Since $g$ is surjective, there is a $a \in A$ such that $g(a)=b$.  Hence, for all $c \in C$ there is an $a \in A$ such that $(f \circ g)(a)=f(g(a))=f(b)=c$.    (c)  This is false.  Let $A=\{1\}$, $B=\{1,2\}$, and $C=\{1\}$. Define $g(1)=1$ and $f(1)=f(2)=1$. Then $f \circ g$ is injective, but $f$ is not injective.    (d)  This is true.  Let $a,b \in A$ where $a \neq b$.  If $(f\circ g)(a)\neq(f\circ g)(b)$, then $f(g(a))\neq f(g(b))$.  Hence $g(a) \neq g(b)$.  (e)  Since $f \circ g$ is surjective, then for every $ c \in C$ there is an $a \in A$ such that $f(g(a))=c$.   Let $b = g(a)$.  Then $b \in B$ and $f(b)=g(f(a))=c$.  Thus $f(b)=c$.  Hence $f$ is surjective.  (f)  Using the same set up as part (c), we have that $g$ is not surjective since there is nothing in $A$ such that $g$ will go to 1. What is the difference between "du -sh *" and "du -sh ./*"? What's the difference between du -sh * and du -sh ./* ?  Note: What interests me is the * and ./* parts. Can I change some but not all Apple keyboard function keys (dim vs F1, bright vs F2)? I want to override F1 and F2 behavior, since I have external display and Mac can't control display's brightness. The rest of the keys should retain their non Fx  I know about "Use all F1-F12 keys as standard function keys.", but I don't want to change all of the keys to be F when pressed, just some of them. (For me single press music and volume control is necessary.)  Is there a way to pick some of the function keys to default to numbered function instead of the "Apple" definitions system wide? If the positive series $\sum a_n$ diverges and $s_n=\sum\limits_{k\leqslant n}a_k$ then $\sum \frac{a_n}{s_n}$ diverges as well So I've been trying to figure out how to prove the following.     Let $(a_n)$ be a sequence of positive numbers such that $\sum\limits_{n=1}^\infty a_n =\infty$, and define $s_n=\sum\limits_{i=1}^n a_i$. Then $\sum\limits_{n=1}^\infty\frac{a_n}{s_n} =\infty$ as well.   I can prove it by comparing it to $\int_1^\infty \frac{1}{x} \, dx $ if the sequence $a_n$ is bounded by some $M$, but that's as far as I've been able to get. How to force the browser to reload cached CSS and JavaScript files What is the exact difference between a 'terminal', a 'shell', a 'tty' and a 'console'? I think these terms almost refer to the same thing, when used loosely:   terminal shell tty console   What exactly does each of these terms refer to? Show that if $a$ is an odd integer and $b$ is an even integer then $\gcd(a,b)=\gcd(a,b/2)$ Show that if $a$ is an odd en integer and $b$ is an even integer then $\gcd(a,b)=\gcd(a,b/2)$.  I understand that since $a$ is not divisible by $2$ but $b$ is, the gcd of $a$ and $b$ also can't be divisible by $2$ but I'm getting stuck using this to help me. I know how to draw different shapes using tikz, like this:  \documentclass{minimal} \usepackage{tikz} \begin{document}  \begin{tikzpicture} \draw (0,0) ellipse (1 and 1.5)       (0,2.5) circle (1)       (2.5,0) circle (1.5); \end{tikzpicture}  \end{document}     However, I would like to put a number of different shapes together inside a node, and I couldn't yet find a simple way to do that. I will make a little figure to include in a large diagram which is already made of several nodes.  If this is not possible, or not easy, then how do I include a JPG or EPS file in a node?  Thank you! Linux file access monitoring Is there any way in unix to find out who accessed certain file in last 1 week? It may be user or some script ftp it to some other place. Can I get a list of user name who accessed certain file? How can I find out who is accessing particular file?? What word describes random unfitting accusations I really dont know how to describe this. Im having a discussion with someone, I was sharing information that I found on a topic. Randomly im called out as being rude when nowhere was there evidence of rudeness exchanged. This person seems to have a history of claiming people have a problem or are being rude out of the random blue.   Is there a word to describe these random accusations that dont connect to anything? Turn off paragraph indention for a single line Is it possible to turn off the paragraph indention for a single line? I have the following use case: I open a new section which describes the task of an exercise. Since I use the font size \large for the section I don't want to use the section text for the task description.  Therefore I added the task description after the section. The disadvantage is that an indention is created when starting to write text after the task description.  What are possible solutions to this problem? Should I use a canonical link which refers to the current URL with pagination?