Installation from USB frozen
What is the proper way of creating installation media from Ubuntu iso?
How do you detect where two line segments intersect? MacOS High Sierra: An error occurred while verifying firmware How to remove top and bottom whitespace of longtable? I am using longtable instead of tabular environment and noticed that it puts some additional whitespace at the top and at the bottom of the table. Is there some way to remove it (something less hacky than \vskip -\baselineskip before the table)?  Small piece of code for illustration:  \documentclass[12pt]{book} \usepackage{longtable}  \begin{document}  Linelineline  \begin{longtable}{l l} cell1 &amp; cell2 \end{longtable}  Linelineline  \begin{tabular}{l l} cell1 &amp; cell2 \end{tabular}  Linelineline  \end{document}   And that's what I am getting:    Common tabular environment does not have any additional margins, but longtable does. Square roots -- positive and negative It is perhaps a bit embarrassing that while doing higher-level math, I have forgot some more fundamental concepts. I would like to ask whether the square root of a number includes both the positive and the negative square roots.  I know that for an equation $x^2 = 9$, the solution is $x = \pm 3$. But if simply given $\sqrt{9}$, does one assume that to mean only the positive root? And when simply talking about the square root of a number in general, would one be referring to both roots or just the positive one, when neither is specified? Can't start mongod , configured storage engine is 'mmapv1' I try to run mongo v2.6.10 on Ubuntu 16.04 lts:  mongod   And get the result:  mongod --help for help and startup options 2017-09-16T12:15:19.660+0430 [initandlisten] MongoDB starting : pid=15959 port=27017 dbpath=/data/db 64-bit host=mahdi-MS-7808 2017-09-16T12:15:19.660+0430 [initandlisten] db version v2.6.10 2017-09-16T12:15:19.660+0430 [initandlisten] git version: nogitversion 2017-09-16T12:15:19.660+0430 [initandlisten] OpenSSL version: OpenSSL 1.0.2g  1 Mar 2016 2017-09-16T12:15:19.660+0430 [initandlisten] build info: Linux lgw01-12 3.19.0-25-generic #26~14.04.1-Ubuntu SMP Fri Jul 24 21:16:20 UTC 2015 x86_64 BOOST_LIB_VERSION=1_58 2017-09-16T12:15:19.660+0430 [initandlisten] allocator: tcmalloc 2017-09-16T12:15:19.660+0430 [initandlisten] options: {} 2017-09-16T12:15:19.660+0430 [initandlisten] exception in initAndListen: 28574 Cannot start server. Detected data files in /data/db created by storage engine 'wiredTiger'. The configured storage engine is 'mmapv1'., terminating 2017-09-16T12:15:19.660+0430 [initandlisten] dbexit:  2017-09-16T12:15:19.660+0430 [initandlisten] shutdown: going to close listening sockets... 2017-09-16T12:15:19.660+0430 [initandlisten] shutdown: going to flush diaglog... 2017-09-16T12:15:19.660+0430 [initandlisten] shutdown: going to close sockets... 2017-09-16T12:15:19.660+0430 [initandlisten] shutdown: waiting for fs preallocator... 2017-09-16T12:15:19.660+0430 [initandlisten] shutdown: lock for final commit... 2017-09-16T12:15:19.660+0430 [initandlisten] shutdown: final commit... 2017-09-16T12:15:19.660+0430 [initandlisten] shutdown: closing all files... 2017-09-16T12:15:19.660+0430 [initandlisten] closeAllFiles() finished 2017-09-16T12:15:19.660+0430 [initandlisten] dbexit: really exiting now   error :     exception in initAndListen: 28574 Cannot start server. Detected data   files in /data/db created by storage engine 'wiredTiger'. The   configured storage engine is 'mmapv1'., terminating   after update mongodb show error . Is there a conventional wisdom to what gear a bike should be left in, when used infrequently? I downloaded the July 30th update for Pokemon Go and when I open the app I'm prompted to login, But once I login, it redirects me to this page on Cookies::     If I click "Done" in the top left, it prompts me to login again! I've tried reinstalling the game, restarting my phone, etc. I can't much enable Cookies on the inline Safari browser. It doesn't make sense, and cookies are on in Safari (because I don't use Safari and they're enabled by default).  How can I fix this? I understand the purpose of up/downvoting answers -- some answers are better than others, some answers may be wrong, .etc.  With regard to questions, though, there are other mechanisms to deal with "bad" questions:  comments, close, flag.  A poorly written question should be improved.  A bad question should be closed/deleted.  Often, though I see poorly written questions downvoted. I'm not sure what this accomplishes.  I get loss of rep for offensive or spam questions, but for an off-topic question?  or one that is just poorly written?   Why?  It seems to me that rep ought to be based more on answers on a site of this type.   Fundamentally, it seems that rep ought to be based on what you add to the site, not what you ask of it.  A particularly good question does add to the site, but a poor question doesn't really detract from it in the same way that a bad (wrong) answer does. Sure, go ahead and give people more rep for asking a particularly good question, but why punish people for asking bad questions when there are other ways of handling that.  Why not handle questions more like comments and allow upvotes, but not downvotes?  It seems to me that many, if not most, of the downvoted questions are first timers.  It's more likely that your first introduction to the site will be in asking a question, rather than answering. There is a significant risk to alienating new users when their questions are downvoted -- there's a visceral response to seeing that negative number next to your question.  Why not let the close/flag system weed out questions that don't belong and the comment system work to improve poorly worded questions. Multiple submit buttons in an HTML form Let's say you create a wizard in an HTML form. One button goes back, and one goes forward. Since the back button appears first in the markup when you press Enter, it will use that button to submit the form.  Example:    &lt;form&gt;   &lt;!-- Put your cursor in this field and press Enter --&gt;   &lt;input type="text" name="field1" /&gt;    &lt;!-- This is the button that will submit --&gt;   &lt;input type="submit" name="prev" value="Previous Page" /&gt;    &lt;!-- But this is the button that I WANT to submit --&gt;   &lt;input type="submit" name="next" value="Next Page" /&gt; &lt;/form&gt;     I would like to get to decide which button is used to submit the form when a user presses Enter. That way, when you press Enter the wizard will move to the next page, not the previous. Do you have to use tabindex to do this? So I understand that Euclidean distance is valid for all of properties for a metric. But why doesn't the square hold the same way? Why is the observable universe so big? How to force the user to download a file, not to view it? I have a project where I have a few layers (State of Texas, cities, roads, etc.). They are all resaved and projected to NAD83 / UTM zone 14N EPSG: 26914. The project CRS is also NAD83 / UTM zone 14N EPSG: 26914 and on the fly projection is enabled. I added a text delimited file and cannot get them to line up. I checked the attribute table of the delimited file and the coordinates are correct. I cross-checked this with a point close to where a few of the points from the delimited file are and they are very close so in theory they should be lining up. I tried to save the delimited file and save it with the same projection and add the shp file back in and that did not work. Anyone have any ideas? I can't think of anything else to try. System.ListException: Before Insert or Upsert list must not have two identically equal elements - Deep Dive what is the total number of distinct arrangements of $n$ oranges and $n$ apples around a round table? I have no idea how to go about. Why is the empty set considered an interval? What is the definition of an interval and why is the empty set an interval by that definition? What should be the default title case for non-technical questions? As an example, this question is titled using sentence case. I've been going to lots of different meta sites (especially this one), and I think the needle bent on my oh-me-oh-my-my-ocd-oh-meter.  Can we please standardize on using either:   Sentence case Title Case AP Style Title Case   ... and then we can look at just converting titles automatically? This would be a switch, of course, but I'd only imagine turning it off on sites where program code or symbols might be present in titles. Or, it could just become part of editing guidelines.    Additionally, is this a horrible idea?   To see the differences between them, you can put any arbitrary title into  (we have no affiliation with them, it's just a tool I sometimes recommend to people).  We would also eventually adopt this for static routes, but I'm mostly talking about questions. LibVLC.NET in GTK# I have one script to allow for one user to run. The string calling it from the command line looks like  ./script path/to/folder -a option='value'   When I try to add it to the other commands in Cmnd_Alias line, sudo blames sudoers file for incorrect syntax. How can I set such commands properly? Primitive polynomials I am revising for a discrete mathematics exam and as quite stuck on this question.  Show that the polynomial $f = x^2 + 2 x + 3 \in \mathbb{Z}_5[x]$ is primitive. How many monic primitive quadratic polynomials are there in $\mathbb{Z}_5[x]$?  Any help would be greatly appreciated.