I have dd crashing after running a few hours.  Typically with a message like  Input/output error 68424+1 records in 68424+1 records out 342124883968 bytes (342 GB) copied, 5114.68 s, 66.9 MB/s   Is there something I can do about it?  Is there some way I can use the output? Or restart where it left off?  Is there any reason to think it is because the partition being backed up is being used?  It always crashes around 70-80%, often when the partition should be less-used.  Since this process takes so long, it is difficult to try different things.  I output to an image.  I could probably use a partition, but LVM is involved:  sudo lvmdiskscan /dev/centos/swap [       3.89 GiB]  /dev/sda1        [     500.00 MiB]  /dev/centos/root [      50.00 GiB]  /dev/sda2        [     465.27 GiB] LVM physical volume /dev/centos/home [     411.38 GiB]  /dev/sdb1        [     931.51 GiB]  3 disks 2 partitions 0 LVM physical volume whole disks 1 LVM physical volume   dd conv=sync,noerror if=/dev/centos/home bs=2000000   of=/run/media/ob/X_1T_Media1GHD-PCTU3/c/sd9e22_cel.image dd: error reading '/dev/centos/home': Input/output error 171062+1 records in 171063+0 records out 342126000000 bytes (342 GB) copied, 4625.3 s, 74.0 MB/s 220856+2 records in 220858+0 records out 441716000000 bytes (442 GB) copied, 6138.1 s, 72.0 MB/s   Friday Morning  ddrescue --sector-size=2048 --cluster-size=$((256*512)) --sparse --verbose /dev/centos/home /run/media/ob/X_1T_Media1GHD-PCTU3/c/sd7c_dd.image /run/media/ob/X_1T_Media1GHD-PCTU3/c/sd7c_dd.map  GNU ddrescue 1.18.1 About to copy 441714 MBytes from /dev/centos/home to /run/media/ob/X_1T_Media1GHD-PCTU3/c/sd7c_dd.image     Starting positions: infile = 0 B,  outfile = 0 B     Copy block size: 131072 sectors       Initial skip size: 32 sectors Sector size: 2048 Bytes  Press Ctrl-C to interrupt rescued:   441714 MB,  errsize:    8192 B,  current rate:        0 B/s    ipos:   342124 MB,   errors:       1,    average rate:   60675 kB/s    opos:   342124 MB, run time:    2.02 h,  successful read:       9 s ago Finished    But   extundelete sd7c_dd.image  --restore-directory /home/ob/p -o /tmp/tt extundelete: Bad magic number in super-block when trying to open filesystem sd7c_dd.image   /dev/mapper/centos-home on /home type xfs (rw,relatime,attr2,inode64,noquota)
How do I backup a LVM partition to an image for recovery purposes?  I am trying to run dd on /dev/sda2, but it crashes after ca 8 hours, at around 380G   sudo lvmdiskscan   /dev/centos/swap [       3.89 GiB]    /dev/sda1        [     500.00 MiB]    /dev/centos/root [      50.00 GiB]    /dev/sda2        [     465.27 GiB] LVM physical volume   /dev/centos/home [     411.38 GiB]    /dev/sdb1        [     931.51 GiB]    3 disks   2 partitions   0 LVM physical volume whole disks   1 LVM physical volume   Anyway, could running from a stick make any difference?
Intuitively it's easy, but hard to prove by the epsilon-delta method:  $$ \lim_{n \to \infty} n x^{n} = 0$$ What should we do with old, very popular closed questions? Motivated by the deletion of     On one hand, I disagree with these closures, because:  These questions were (and still are) very popular They have some good information in them (or at least the first one does) and it feels like bad sportsmanship to remove good information from the internet, particularly when it was contributed by your fellow users  Number 2 in particular bothers me. A lot. On the other hand, I do agree that:  The community of 10k users should be able to decide which closed questions they wish to delete on their own without me intervening These questions should definitely remain closed, because they either have an absurd # of answers, or are duplicates (though some duplicates ). Which means they are eligible for deletion … forever. These questions wouldn't survive more than 10 minutes if asked today on Stack Overflow, so in some ways they are artifacts from the past, like dinosaurs in an era of mammals.  There is some related discussion in:   While I normally favor code solutions here, I am not sure I like the idea that once a question gets 400 upvotes it should become extremely difficult to delete. It feels like mob rule. Official policy on the blog: Problem with package lineno I'm using package lineno for proofreading of my documents.  So I usually have something like the following MWE:  \documentclass{article}  \usepackage{blindtext}  \usepackage{ifthen}           % to use if then else \newboolean{korrektur}        % for proofreading: true/false  \setboolean{korrektur}{true} % choose one, comment the other %\setboolean{korrektur}{false}  % What we need for proofreading \ifthenelse{\boolean{korrektur}}% proofreading wanted? {% YES:   \usepackage{showframe}          % shows type area   \usepackage{lineno}             % numbers lines   \pagewiselinenumbers            % lines per page }% {% NO: % error if lineno was used before:   \typeout{***** Please delete .aux files if you get errors! *****} % What to add here so that I get no errors?  %&lt;================= }  \begin{document} \Blindtext \end{document}   Run it two times. Everything should be well, blindtext is numbered.  Now please move the % sign from line 8 (false) to line 7 (true).    Because we had had the run before there is an .aux-file, including lines with the macro \@LN.  If you compile now you will get the following error message (and some more):   ***** Please delete .aux files if you get errors! ***** (C:\Users\...\LaTeX\_TeX.SX\lineno\test-lineno.aux ! Undefined control sequence. l.2 \@LN         {0}{0}   Question:  Is it possible to add in line 20 (see %&lt;===========) something to get rid of the error messages? Something that resets the meaning of macro \@LN? I want to advance in the ranks of Senator Lavigny-Duval. How can I get merit points? I know I can participate in expansion goals, but is there a better way than that? The the title is self explanatory, I guess.  Why can two (or more) electric  never cross? Evaluate $\lim_{n\to\infty} [{1\over kn}+{1\over k(n+1)}+{1\over k(n+2)}+\cdots+{1\over k(n+p-k)}]$ where $k<p$ There are four options. Which of them is correct?- (a)${p\over k}$ (b)${k\over p}$ (c)$\log({p\over k})$ (d)${\log p\over k}$ I somehow want to use the rule for evaluating this kind of sum using integration, i.e. $\int_{0}^{1} f(x) \ dx=\lim_{n\to\infty} {1\over n}\sum_{r=1}^{n}f({r\over n})$  But the given expression $\lim_{n\to\infty} [{1\over kn}+{1\over k(n+1)}+{1\over k(n+2)}+\cdots+{1\over k(n+p-k)}]={1\over k}\lim_{n\to\infty}{1\over n}\sum_{r=0}^{p-k}\frac{1}{1+{r\over n}}$, sum running from $0$ to $p-k$ instead of $n$. So, how to evaluate this limit? Thanks for assistance in advance. If string is stretched just by weight, where does the gravitational potential energy goes if only half is converted to elastic potential energy? If a spring is stretched by a weight of mass m, (so the extension is $\Delta x$) then $ k = \frac W{\Delta x} = \frac {mg}{\Delta x}$. So $ k\Delta x= mg $.  When the Spring is stretched by distance $\Delta x$ (by the weight) then it looses gravitational potential enegry. ($ \Delta GPE= mg\Delta x$)  But, when we calculate the change in elastic potential energy, We get  $ U = \frac 12 k(\Delta x)^2 $. Since $ k\Delta x = mg$, $U=\frac 12 mg\Delta x$  At, equilibrium we have no kinetic energy $E_k = 0$  Doesn't that violate Energy Conservation?  Where does the rest of lost GPE goes?  Here's a illustration Is it possible and if so how can you pass flags to the ShareLaTeX compiler which one would have passed as parameters to the LaTeX compiler?  I am using the minted package and need to pass the -shell-escape flag. Possible Duplicate:          I was wondering if there's any good reason to still use blob fields in a database. A couple of years ago I worked with a DB with a bunch of images in it, the DB was very slow and I couldn't see any good reason to keep the images inside the DB, so I got the images out and stored the filenames instead.  Was this a smart move? What would you do in my place? Zip folder without including path to folder and require only one argument I'm trying to make a zip function that'll do all the steps I typically do when zipping a file or folder. Say my current directory is ~, and I want to zip a folder named Folder1, whose file path is ~/Folder2/Folder1.  Issuing  cd ~/Folder2 &amp;&amp; zip -r Folder1 Folder1 &amp;&amp; cd -   does exactly what I want. Namely, it zips so that the output Folder1.zip does not contain folders that lead up to the folder I'm zipping (namely, /home/user/Folder2), it zips recursively, and it takes in the first argument of zip with the exact name as the file or folder I'm zipping (Folder1.zip).  So I want to make a function in my .zshrc something akin to  coolerzip() { cd /path/to/file &amp;&amp; zip -r file file &amp;&amp; cd - }   where it need only take in one argument, which in this case, it will be ~/Folder2/Folder1. Then Folder1 will be the name for both files in coolerzip, and I will cd right into ~/Folder2 so Folder1 lies in my current directory before zipping. Is there any way I can achieve this so that coolerzip only requires one argument rather than three? Identify $P(2014)$ if $P(i)=1/i$ for every positive integer $1\le i\le2013$ Suppose $P(x)$ is a polynomial of degree $2012$ and $P(x) = 1/x$ when $x$ takes the integer values $1\cdots2013$ (inclusive). What is the value of $P(2014)$?   I get $1/1007$ but I'm not sure if it's right, and my method is very inelegant. I'm working on a project using logistic regression to predict student retention. The data were collected through three self-report instruments. We are trying to find out which predictors are powerful enough to predict the at-risk students. I came across some articles saying a balanced sample (50% stay, 50% dropouts) is desirable for such study, e.g. Glynn, J.G., Sauer, P.L., &amp; Miller, T.E. (2003). , NASPA Journal, 41 (1), 41-67:     A problem however, is that the distribution of the dependent variable is likely to be highly skewed toward persistence. For example, if 85% of the analysis sample were persistors, a classification model that classified every student as a persistor would have a success rate of 85%, or would classify 85% of student correctly. To resolve this issue, the maintenance of relative balance between the number of dropouts and the number of persistors (about 50% each) in the analysis sample was desirable.   Is this true? Our sample only has about 25%-30% dropout students. Will this affect the results? How does gravity work underground? Would the effect of gravity on me change if I were to dig a very deep hole and stand in it? If so, how would it change? Am I more likely to be pulled downwards, or pulled towards the edges of the hole? If there would be no change, why not? By definition a matrix representing a Lorentz transformation is orthogonal, so that its inverse is equal to its transpose.   Consider a pure boost in the t-x plane; $$\Lambda_x=\begin{pmatrix} \cosh(\gamma) &amp;&amp; \sinh(\gamma) &amp;&amp; 0 &amp;&amp; 0\\ \sinh(\gamma) &amp;&amp; \cosh(\gamma) &amp;&amp; 0 &amp;&amp; 0\\ 0 &amp;&amp; 0 &amp;&amp; 1 &amp;&amp; 0\\ 0&amp;&amp;0&amp;&amp;0&amp;&amp;1 \end{pmatrix}.$$ $\Lambda_x$ has inverse  $$\Lambda_x^{-1}=\begin{pmatrix} \cosh(\gamma) &amp;&amp; -\sinh(\gamma) &amp;&amp; 0&amp;&amp;0\\ -\sinh(\gamma) &amp;&amp; \cosh(\gamma) &amp;&amp; 0&amp;&amp;0\\ 0 &amp;&amp; 0 &amp;&amp; 1 &amp;&amp;0\\ 0&amp;&amp;0&amp;&amp;0&amp;&amp;1 \end{pmatrix}$$ but tranpose  $$\Lambda_x^T=\begin{pmatrix} \cosh(\gamma) &amp;&amp; \sinh(\gamma) &amp;&amp; 0&amp;&amp;0\\ \sinh(\gamma) &amp;&amp; \cosh(\gamma) &amp;&amp; 0&amp;&amp;0\\ 0 &amp;&amp; 0 &amp;&amp; 1&amp;&amp;0\\ 0&amp;&amp;0&amp;&amp;0&amp;&amp;1 \end{pmatrix}.$$ These are not equal. Where have I gone wrong? I just visited Ask Ubuntu (askubuntu.com) while logged into Stack Exchange, and noticed that "join this community" doesn't appear:    It is similarly broken on Math Overflow (mathoverflow.net). It works, however, on all sites that are subdomains of stackexchange.com, like Mathematics (math.stackexchange.com) and Academia.  I'm using Google Chrome version 46.0.2490.86 on Windows 8.1 Update 1.  (I don't know if this can actually be fixed, given how cookie security works, but I figured Stack Exchange should be aware of the issue.) In a world without air, I understand they definitely would. However, with drag taken into account, I think they wouldn't. Since the drag force varies proportional to the square of speed (ignoring the change in coefficient of drag with speed), wouldn't the total impulse due to drag on a bullet fired from a gun from a specific height horizontal to ground be higher than the total impulse on an identical bullet dropped from the same height with no horizontal velocity?  Also, when bullet spin is taken into account, the bullet fired from a gun should resist change in orientation; therefore, it should maintain a small but non-zero angle of attack, and also have a lift force, correct? I am trying to master the homemade Neapolitan pizza, from dough preparation to cooking it.  After following the recommendations at Seriouseats.com for the dough preparation, I came across some doubts regarding the oven use.  I understand that ideally I would make it in a 900F wood oven, but at home we don't have such equipment!  What is the best practice to make the Neapolitan Pizza in a regular gas oven that heats up to 530F? (i.e. temperature, time, tray positioning...) Are there changes in the way the dough has to be prepared? Google's CDN is nice, but it's not 100% reliable for all users. It occasionally fails to load for me. Other users , and some .  It's one more possible point of failure. It would be preferable if Stack Exchange didn't depend on it.  If you don't want to stop using it, consider adding a fallback if it fails to load. Something like this:  &lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"&gt;&lt;/script&gt; &lt;script&gt;   if (!window.jQuery) {     document.write('&lt;script src="https://cdn.sstatic.net/stackoverflow/content/js/jquery-1.7.1.min.js"&gt;&lt;\/script&gt;');   } &lt;/script&gt; Using past tense when referencing a still-true fact Sharing Test code in Maven How can you depend on test code from another module in Maven?    Example, I have 2 modules:   Base Main   I would like a test case in Main to extend a base test class in Base.  Is this possible?  Update: Found an , which involves creating a test jar.