Unable to install any programs
What is "superuser" and how do I get that privilege?
Should I use the first or last bits from a SHA-256 hash? I have the need for a hexadecimal token that is smaller than the normal length of the hexadecimal representation of a  hash.  Should I take the first bits or the last bits? Which of them contain the most entropy? What is the current state of apple device (iPhone, iPod, etc.) support? Taking notes, I was going to write this:     therefore p′ is a shortest path.   But the topic is APSP which stands for "all pairs shortest paths" so I decided to just write SP instead and...  Is it written with a like this     therefore p′ is a SP   or with an like this (because in my head I would "read" the S)     therefore p′ is an SP Is there a 'rule of thumb' that I can use to estimate depth of field while shooting? I can use a DoF calculator, or crunch the heavy math by hand if I really want to know exactly what my DoF is going to be... but most of the time knowing exactly is actually overkill, and taking the time to pull out a DoF calculator is impractical. I'm wondering if anyone knows of a 'rule of thumb' that is common for quickly figuring out a rough estimate of what my DoF will be when I'm in the field... What is the meaning of the density of a distribution at a point? I know how to use PDFs to calculate probabilities, but I don't think I understand them. For example, at $X=0$ the PDF of the standard normal distribution is $\approx 0.4$. Does this have any useful meaning? Suppose $X_1,\ldots,X_n$ are a random sample of $U(-\theta,\theta)$ with $\theta&gt;0$. How can find $$ E\left(|X_1|\ \big|\max |X_i| \right) $$ that $1\leq i\leq n$? Rules for the usage of "me" VS. "myself"? What are general guidelines for the use of "me" and "myself"?     Did I describe me or did I describe Maria?   OR     Did I describe myself or did I describe Maria? How to tell Google that I have changed my website URLs? I have done major updates to my website, and renamed all my URLs.  How can I tell Google that I have renamed these URLs and let Google refresh its index?  My website URL: http://www.pndmasr.com/  My sitemap: http://www.pndmasr.com/sitemap.xml  I have uploaded my sitemap via Google Webmaster Tools many times.  However, every time I search Google for "pndmasr", I still get results with old pages. I have waited more than 3 days but the problem remains. Any suggestions?  Is there a problem with my sitemap? Is there an idiom for someone who gets what he deserved? Like someone receiving punishment for his evil deeds or someone getting awarded for his good deeds? Selecting the right crank length What is the best way to determine the correct crank length for my height and more specifically my leg length? When we push a box, the box applies an opposite force on my hand, but why does my hand move with the box as I push the box if the net force of my hand is 0? What is happening? I have always argued adamantly, as long as the issue has been around, that gift should never be used as a verb. However, someone whose English knowledge I quite respect disagrees.  I’ve done some searching and I haven’t found a consensus; should gifting be shunned? How can we play split screen in the XBOX 360 version of Minecraft? My little brother and I want to play Minecraft together on the Xbox 360, and we heard there was a split screen option. We've looked inside the options menu but weren't able to find it. Does the game really have a split screen option, and if so, how do we enable it? RMSE vs Standard deviation in population Person, Persons, People, Peoples $$e^{i} = e^{i2\pi/2\pi} = (e^{2\pi i})^{1/(2\pi)} = 1^{1/(2\pi )} = 1$$  Obviously, one of my algebraic manipulations is not valid. Site hosted on EC2 / Amazon held hostage with private key I have a new client whose previous developer has left her high &amp; dry with her site on Amazon/EC2. He holds the private key to the instance, and though she has full access to the Amazon control panel (she's paying $300/mo for a site that has like 3 visitors per week) she doesn't have any way to get her content off and move to a new host.  I'm not familiar with AWS and am not sure how to help her. The site's group/file permissions are screwed up on the server so exporting the content/database via her WordPress control panel isn't working.  Any ideas on how to help her? Thanks! An unclear sentence in the book "Griffiths, Harris-Principles of algebraic geometry" Let $X$ be a complex manifold and consider a holomorphic vector bundle $\pi:E\to X$ of rank $r$. By the usual correspondence between vector bundles and locally free sheaves, we consider $E$ as a sheaf by abuse of notation. We denote with $\mathscr A_X^{p,q}$ the sheaf of $C^\infty$ $(p,q)$-differential forms on $X$ and we define: $$A^{p,q}(E):=\Gamma(X,\mathscr A^{p,q}\otimes_{\mathscr O_X} E)$$ $$A^k(E):=\bigoplus_{p+q=k}A^{p,q}(E)$$  Now suppose that $\nabla:A^\bullet(E)\to A^\bullet(E)$ is a linear connection on $E$, then the curvature operator is defined as: $$\nabla^2:A^0(E)\to A^2(E)$$ where $\nabla^2$ is the composition of the maps $\nabla: A^0(E)\to A^2(E)$   and $\nabla: A^1(E)\to A^2(E)$. One can show that $\nabla^2$ is $C^\infty(X)$-linear.    I don't understand the following sentence from the Griffiths-Harris book at page 75 (I rephrase it by using my notation):     Since $\nabla^2$ is $C^\infty(X)$-linear, then it is induced by a bundle map $E\to\bigwedge^2T^*X\otimes E$, or in other words, $\nabla^2$ corresponds to a global section $\Theta$ of the bundle $\bigwedge^2T^*X\otimes\operatorname{Hom}(E,E)$.   I absolutely don't understand how I can see the operator $\nabla^2$ as the section $\Theta$. ArcPy importing error after setting path? This questions has been asked before too and I did go through most of the suggestions. Things I have tried so far: setting up correct  path variable environment, installing anaconda 32 bits, python 2.7, or even switching to python 2.7 in cmd while initially using Anaconda 3 , adding Desktop 10.4.pth file with  following path.  C:\Program Files (x86)\ArcGIS\Desktop10.4\bin C:\Program Files (x86)\ArcGIS\Desktop10.4\ArcPy C:\Program Files (x86)\ArcGIS\Desktop10.4\ArcToolBox\Scripts   I also added those paths in environment variable   These suggestions help me to reduce the error. But Now I am getting a different error. Looks like python can find arcpy but missing another package.  Getting this error while trying to import arcpy in python 3.6.   File "C:\Program Files (x86)\ArcGIS\Desktop10.4\ArcPy\arcpy\__init__.py", line 22, in &lt;module&gt;     from arcpy.geoprocessing import gp    File "C:\Program Files (x86)\ArcGIS\Desktop10.4\ArcPy\arcpy\geoprocessing\__init__.py", line 14, in &lt;module&gt;     from _base import *  ModuleNotFoundError: No module named '_base'   Any suggestions? vertical alignment of a turned cell I know using turn command and a sample code like this:  \usepackage{rotating}  \begin{turn}{90} Supervised Learning \end{turn}}   we can rotate a text inside a cell, however, I couldn't find a way to vertically center this rotated text. Any suggestions is appreciated.  Here is the sample MWE:  \begin{table}[]     \centering     \begin{tabular}{|&gt;{\centering\arraybackslash}m{0.5cm}|c|&gt;{\centering\arraybackslash}m{8cm}|}         \hline         \multicolumn{2}{|c|}{Classification} &amp; References \\ \hline         %\multirow{2}{*}{{\begin{turn}{90}Supervised Learning\end{turn}}}            \multirow{2}{*}{\rotatebox[origin=c]{90}{Supervised Learning}}  \end{tabular}     \caption{A Classification}     \label{tab:Machine_Learning_models} \end{table}