After a problem on my MacBook Pro (15' 2016), Apple replaced the motherboard with Sierra installed and I can't upgrade back to BigSur. In the App Store, no system upgrade is suggested. If I click on &quot;macOS Big Sur&quot; link from apps.apple.com, the App Store opens with this message:  Can't connect to the App Store  The computer is connected to the internet and the time is correctly set. How can I fix this issue ? Is there any command line to download macOS Big Sur ?
Sometimes it's hard to search for older versions of macOS &amp; OS X  on the App Store.  This is an attempt to provide the canonical QA for this issue, as per the Meta QA -  I expect it to be modified over time to hopefully become a complete information resource.  How can I get any older version of a Mac OS to be able to run as a VM, or to reinstall on my Mac?
"Congratulation" vs. "congratulations" How can I print the table of contents multiple times in my document? I am using also titletoc to improve how my table of contents. I would like to print the table of contents several times. How can I do it?  It does not work in the MWE:  \documentclass{article} \usepackage[utf8]{inputenc}  \begin{document}  \tableofcontents  \section{Hello} \section{Bye}  \tableofcontents  \end{document}     PS: I have this code in my document, in order to have no title for the table of contents.  \makeatletter \renewcommand\tableofcontents{%     \@starttoc{toc}% } \makeatother   PPS: \renewcommand{\contentsname}{}% Remove \tableofcontents' title/name will not work since I am using [french]{babel}. I have to show by induction that this function is a multiple of 8. I have tried everything but I can only show that is multiple of 4, some hints? The function is $$5^{n+1}+2\cdot 3^n+1 \hspace{1cm}\forall n\ge 0$$, because it is a multiple of 8, you can say that$$5^{n+1}+2\cdot 3^n+1=8\cdot m \hspace{1cm}\forall m\in\mathbb{N}$$. Obtain user and kernel time of a running process? Is there way to determine using standard Linux/Unix tools how much a process has spent in User mode and how much waiting for kernel?  In other words, exactly the "user" and "sys" values that you get when using time, but during process runtime?  NOTE: one way is to use WBEM and enumerate Linux_UnixProcess, but I need to use other tool than this; my aim is to verify what WBEM provider tells me, i.e. I need to use different tool. Right at the beginning of the game, Meowth comes into your room and attempts to wake you up. At this point, I assume I have to press some button to get out of bed, but the D-Pad or A button doesn't do anything, nor any of the other buttons. How do I get out of bed to start the game? What files should i put in a logo pack to give to clients? Should I put small, medium and large version of my logo as well as the vector file. How will old M42 lenses work on a Nikon camera? Who did Khan get his Starfleet insignia from? Let $ a_{n} = \sum_{k=1}^{n} \frac{n}{n^{2}+k}$ . I would like to know whether the given sequence converges.   I see  that,  $ a_{n} = \sum_{k=1}^{n} \frac{n}{n^{2}+k}= \sum_{k=1}^{n} \frac{1}{n+\frac{k}{n}}.$ When $n$ gets sufficiently large the contribution by the $ \frac{k}{n} $ term is diminishing and $ a_{n} &lt; \sum_{k=1}^{n} \frac{1}{n} = 1 $.   Thank you. Taking back turns, and forgotten privileges How to setup Squid Proxy (for localhost services and Tor and I2P) Why does an argument similiar to 0.999...=1 show 999...=-1? I accept that two numbers can have the same supremum depending on how you generate a decimal representation. So $2.4999\ldots = 2.5$ etc. Can anyone point me to resources that would explain what the below argument that shows $999\ldots = -1$ is about? Here is the most usual proof I see that $0.999\ldots = 1$:  $x=0.999\ldots$ $10x=9.999\ldots$ $10x - x = 9$ $x=1$  Using this same argument template I can show $999\ldots=-1$:  $x= \ldots9999.0 $ $0.1x= \ldots9999.9$ $0.1x - x = 0.9$ $x=-1$  What might this mean? Edit from one of the comments: $$\sum_{k=0}^{\infty}{9 \cdot 10^k}=-1$$ In a question earlier today () the Op asserts that they would need to change their hub, if they wanted to go from a 10- to 11- speed cassette.  I'm not very clued up on 11-speed systems, was wondering why this is the case? And, presumably, when they say "hub", they mean just the freehub body?    Or do they mean something else/more? Direct way leads to nowhere.  $$\lim_{n\rightarrow \infty} \sum^{n}_{i=1} \frac{1}{\sqrt {n^2 +i} } = \lim_{n\rightarrow \infty} \sum^{n}_{i=1} \frac{1}{n \sqrt {1 +\frac{i}{n^2}} } = $$  $$ = \lim_{n\rightarrow \infty} \frac{1}{n} \cdot \lim_{n\rightarrow \infty} \sum^{n}_{i=1} \frac{1}{\sqrt {1 +\frac{i}{n^2}} } = 0 \cdot \sum^{n}_{i=1} 1 = 0 \cdot n $$  So, I tried to apply squeeze theorem:  $$\lim_{n\rightarrow \infty} \sum^{n}_{i=1} \frac{1}{\sqrt {n^2 +i} } \leq \lim_{n\rightarrow \infty} \sum^{n}_{i=1} \frac{1}{n}  = 1$$  Could you help me to figure out the lower bound? How do I convert between big-endian and little-endian values in C++? For clarity, I have to translate binary data (double-precision floating point values and 32-bit and 64-bit integers) from one CPU architecture to another.  This doesn't involve networking, so ntoh() and similar functions won't work here.  Note: The answer I accepted applies directly to compilers I'm targeting (which is why I chose it).  However, there are other very good, more portable answers here. With ksh I'm using read as a convenient way to separate values: $ echo 1 2 3 4 5 | read a b dump $ echo $b $a  2 1 $  But it fails in Bash: $ echo 1 2 3 4 5 | read a b dump $ echo $b $a     $  I didn't find a reason in the man page why it fails, any idea? $ \lim_{x\to o} \frac{(1+x)^{\frac1x}-e+\frac{ex}{2}}{ex^2} $ $$ \lim_{x\to o} \frac{(1+x)^{\frac1x}-e+\frac{ex}{2}}{ex^2} $$   (can this be duplicate? I think not) I tried it using many methods  $1.$ Solve this conventionally taking $1^\infty$ form in no luck  $2.$ Did this, expand $ {(1+x)^{\frac1x}}$ using binomial theorem got $\frac13$ then grouped coefficients of $x^0$ and it cancelled with $e$ then took coefficient of $x$ cancelled with $\frac{ex}{2}$ and so on   very messy right ? at last I got $\frac13$ but that's not the expected answer!  I must have went wrong somewhere can anyone help me with this. How can I convert raster (stream segments result of a watershed analysis) to vector polylines, preferably shapefile. In ArcGIS this is easily acomplished with the Raster to Polyline tool.  I only see Polygonize (Raster to Vector) tool under the Raster -> Conversion menu. Mapping Russia - Int'l dateline splitting polygon Including .eps figure in PDFLatex This question has been asked a lot, but for reason I cannot get it to work. I'd like to include a .eps image in my document - I am using pdflatex in TeXMaker. Below is the input (I am providing the whole preamble incase there is some interference.   \documentclass[11pt]{article} \usepackage{times} \usepackage{graphicx} \usepackage{epstopdf} %converting to PDF \usepackage{amssymb} \usepackage{amsmath} \usepackage{mathtools} \newcommand{\HRule}{\rule{\linewidth}{0.5mm}} \usepackage[parfill]{parskip} \setcounter{secnumdepth}{5} %how deep sections are numbers \usepackage{float} \usepackage[font={sf,footnotesize},labelfont=bf, justification=justified, singlelinecheck=off]{caption} \usepackage[font=footnotesize]{subcaption} \usepackage[scaled]{helvet}  \usepackage{titlesec}  \usepackage[T1]{fontenc} \usepackage[export]{adjustbox} %for large figures \usepackage{upgreek} \usepackage{microtype} \usepackage{setspace} \singlespacing \usepackage[defaultlines=4,all]{nowidow}  \includegraphics[scale=1]{/../model_1_2.eps}    The error I get is:      ! Package pdftex.def Error: File `/model_1_2-eps-converted-to.pdf' not   found.See the pdftex.def package documentation for explanation.Type H    for immediate help.... .../../model_1_2.eps}   I hope someone can help.