I just installed Ubuntu Linux (16.04 LTS) last night. This is the first copy of Linux I've installed. I did use Linux for maybe a few weeks over 10 years ago, but I was very young at the time and didn't really understand its significance.  One of the first things I wanted to do after using this operating system was remove the guest login feature out of an abundance of caution.  I did a Google search and came across this website that instructs one to enter a couple lines of code into a terminal window to remove the feature:   I wish I had done more research on the issue before entering this code (I guess since the domain looked legitimate, it showed up among the first Google Search results, the author seemed knowledgeable, and the code didn't "look" malicious, I assumed everything would work out the way it should). But, upon entering the first code and entering my password (see the code below), I got an error message that said the directory or file already exists. This is the code in question:   sudo mkdir /etc/lightdm/lightdm.conf.d   As I said, I believe the error message was letting me know that file or directory already exists. I then read the comments on the post and saw that people found inaccuracies in the code.  But when I entered the second piece of code (see below), I did not get an error message. Upon restarting my computer, the guest login feature was removed. The code:   sudo sh -c 'printf "[SeatDefaults]\nallow-guest=false\n" &gt; /etc/lightdm/lightdm.conf.d/50-no-guest.conf'   For posterity's sake, this is how the author recommends reverting the code to bring back the guest login feature:   sudo rm /etc/lightdm/lightdm.conf.d/50-no-guest.conf   My concern is that, since the first piece of code seemed to give an error message or the like, this code may have done something untoward to the operating system. Could someone let me know if this is the case, or reassure me if it's not?  EDIT: 2017-07-05 @ 20:20 UTC  See also this newer thread that addresses my questions, "How Do I Revert Ubuntu 16.04 LTS to Its Original State? Is a Clean Install Necessary?"
How do I disable the guest session in Ubuntu 11.10 or higher? I don't want people to be able to use my computer without using a password to log in!
A world where nothing can be hidden. No lies, always truth In a Bollywood movie Pk, a man comes from a planet where lying is not possible as all the thoughts/knowledge is transferable via human contact. Due to which they do not have to lie about anything or hide anything from each other.  Say, such a society plausible with technology, if we decide to abandon the privacy as we know today. All the recorded data (written, spoken, recorded videos etc.) and thought (via neuralink) is accessible to everyone, everywhere.  Basic idea behind the question is, people worry about data being accumulated at one place (entity or government) and being used against them or to deceive them. If everything is accessible/known to everyone of about anyone and anything, what does privacy mean in this case? Recently I commented on  question   and the text did got bold but the italic word didn't seem to get italic on Android Chrome(Latest Ver.), but when I saw from the PC browser, it rendered as it should...  I've attached a screenshot of my phone ... Counting the number of surjections. You can reach this IP address  (if my computer is online). I want to assign a domain to it so I wonder how is that possible when I have no DNS? I do own my domain which is ".com". My IP is static.  Thanks Predicting the number of decimal digits needed to express a rational number Reading a file used by another process How can Linux/Ubuntu be installed safely on ChromeBook? Is installing Ubuntu on my Chromebook potentially dangerous to anything on my Chromebook? I got it as a gift, so I don't want to destroy anything that is important on the laptop. Also, which is better for being able to safely install Ubuntu: ChrUbuntu or Crouton? I'm using the Samsung Chromebook 3 (as described by the quick-start manual). Does that make any other differences as well? Why did my windshield freeze instantaneously? Is 60 minutes enough layover time at Los Angeles International Airport? I am flying in to LAX on American Airlines and have a 60 min layover before I fly out with American Airlines (same ticket).  Will this be enough time? Could there be an eighth Horcrux? Calculation of number density from material density Material density is given by $ \rho =m/V$, where $m$ is mass and $V$ is volume. Again number density given by $n=N/V$, where $N$ is the total number of particle. How can I calculate number density $n$ from material density $ \rho $. What will reduce my rendertime? What would reduce the render time? Should I get a better GPU or more RAM? Re-entering the US for the third time in a year with total of 240 Days I went to the US for 90 days on an ESTA in August to November. Then back to my home country for 1 month and then back again mid December until mid February and now I am going back again after 10 days for another 90 days. Now I can see that some people refer to 180 day rule in a year. My stay will be 240 days in one year with short gaps between coming back. Is the 180 day rule accurate? Some people write that you can do unlimited trips to The US as long as you don't stay more than 90 days. Is that correct? My reason for going there the first time was to visit and travel with an American friend.  After my first visit (she is my girlfriend) moved with me to my home country but has ended up in a custody battle in the US so she needed to return urgently so I returned only to be with her and support her, not to be a tourist.  Then after my second visit I needed to go back to my sick Dad and to rent out my apartment since we left in a rush to go back to the US.  Now, my third visit is to continue to be with my girlfriend and support her in her difficult situation.   My question is, if I do end up in trouble should I tell them this whole story? Or should I just say I am visiting a friend for a third time because I want to see more of the country and I have some more time off before I go back to my job.  I have proof of money in my bank account and I stay and eat with her for free Documented proof that I have a job to return to in my home country My return ticket printed and an address to stay at in the US and I have proof I have an apartment in my home country So far, I know if $p$ is a rational prime, then $(1)$ if $p\equiv 3\mod4$, then $p$ is prime in $\mathbb{Z}[i]$. $(2)$ If $p\equiv1\mod4$  then $p=π_1 π_2$ where $π_1 $ and $π_2$ are conjugate, Then $π_1 $ and $π_2$ are primes in $\mathbb{Z}[i]$. $(3)$ $2=(1+i)(1-i)$, then $(1+i)$and$(1-i)$ are primes in $\mathbb{Z}[i]$.  What's are all the prime elements in Gaussian integers $\mathbb{Z}[i]$? For example, $-3$ are prime in $\mathbb{Z}[i]$, but not in the above $3$ cases. I found  presentation document by D. J. Bernstein. Is it possible to create it in latex?  Screenshot Missing argument 2 for wpdb::prepare() Issue I'm having to update a WP installation for a community organisations from version 2.9.1 to the current 3.9.1.   The installation has a couple of custom built plugins that aren't documented.  I've just performed the WP version update and now I see a warning (Missing argument 2 for wpdb::prepare()) on every page that relates to the following line in the code of one of these custom built plugin:  $rows = $wpdb-&gt;get_results($wpdb-&gt;prepare("SELECT id, name FROM ".$table_name));   From what I've read online, this is due to a change in the coding, that requires 2 values to be sent to wpdb::prepare(), but I've no idea how the line of code given above, needs to be changed.  If someone could help me out, I'd really appreciate it. I am creating a custom form on a Salesforce Marketing Cloud Landing Page. This page will have information such as Email address, first name and last name pre-filled from an email, however there will be some cases where emails can be entered by the customer. What is the best way to validate email addresses on form submit? E.g. a regex to look at overall structure or is there a better way? Legal issues for a "fangame" of a commercial franchise? I've played around in the past of the 2D Flash fan-made version of the popular Valve game Portal.  It has basically the exact same mechanics, but as a 2D side-view flash game.  Lately I've toyed around with creating a simplified flash version of some of my favorite franchises (such as Zelda, Mario, Splinter Cell, etc.).  Of course, nothing is "stopping" me from just using the same mechanics and just changing the name to something not copyrighted.  I have witnessed projects that have tried to directly port a 3D game into a 2D simplified version, with the exact same plot and puzzles (Ocarina of Time in 2D comes to mind), and I have seen them being shut down.  But I am not likely going to exactly duplicate any game...just borrow some of the source material and basic underlying mechanics.  For example, if I were to make a Zelda-influenced fan game, I would have items such as the Hookshot, Boomerang, and all other sorts of ones from the Gameboy Zeldas; just with a custom plot and dungeons.  With likely the same mechanics.  What are the legal issues involved in this?  I used to think it was a "Don't do this ever; it's a bad idea."  But then I've seen the Portal clone, and now I'm curious. How do I install OpenStack? How do I install ? Is there an easier way other than official installation instructions? How can I convert a string of bytes into an int in python?   Say like this: 'y\xcc\xa6\xbb'  I came up with a clever/stupid way of doing it:  sum(ord(c) &lt;&lt; (i * 8) for i, c in enumerate('y\xcc\xa6\xbb'[::-1]))   I know there has to be something builtin or in the standard library that does this more simply...  This is different from  for which you can use int(xxx, 16), but instead I want to convert a string of actual byte values.  UPDATE:  I kind of like James' answer a little better because it doesn't require importing another module, but Greg's method is faster:  &gt;&gt;&gt; from timeit import Timer &gt;&gt;&gt; Timer('struct.unpack("&lt;L", "y\xcc\xa6\xbb")[0]', 'import struct').timeit() 0.36242198944091797 &gt;&gt;&gt; Timer("int('y\xcc\xa6\xbb'.encode('hex'), 16)").timeit() 1.1432669162750244   My hacky method:  &gt;&gt;&gt; Timer("sum(ord(c) &lt;&lt; (i * 8) for i, c in enumerate('y\xcc\xa6\xbb'[::-1]))").timeit() 2.8819329738616943   FURTHER UPDATE:  Someone asked in comments what's the problem with importing another module. Well, importing a module isn't necessarily cheap, take a look:  &gt;&gt;&gt; Timer("""import struct\nstruct.unpack("&gt;L", "y\xcc\xa6\xbb")[0]""").timeit() 0.98822188377380371   Including the cost of importing the module negates almost all of the advantage that this method has. I believe that this will only include the expense of importing it once for the entire benchmark run; look what happens when I force it to reload every time:  &gt;&gt;&gt; Timer("""reload(struct)\nstruct.unpack("&gt;L", "y\xcc\xa6\xbb")[0]""", 'import struct').timeit() 68.474128007888794   Needless to say, if you're doing a lot of executions of this method per one import than this becomes proportionally less of an issue. It's also probably i/o cost rather than cpu so it may depend on the capacity and load characteristics of the particular machine.