I am having this issue with a brand new Ubuntu 16.04.2 Virtual Machine.  apt-get updates fails with this error  $ sudo apt-get update -o Debug::Acquire::http=1 -o Debug::pkgAcquire::Auth=true -o Debug::Hashs=trueenter  0% [Connecting to archive.ubuntu.com]GET /ubuntu/dists/xenial/InRelease HTTP/1.1 Host: archive.ubuntu.com Cache-Control: max-age=0 Accept: text/* User-Agent: Debian APT-HTTP/1.3 (1.2.19)   Answer for: http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease HTTP/1.1 200 OK Content-Type: text/html; charset="utf-8" Content-Length: 2832 Connection: Close  Get:1 http://archive.ubuntu.com/ubuntu xenial InRelease [2,832 B] 0% [1 InRelease 2,832 B/2,832 B 100%]201 URI Done: http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease ReceivedHash:         - SHA512:9a57e33cddb5b821ee529e7e4e39d1039f260b1b3ceee28902b7e595dfcb95280f87f45a88f433b452657f725c6a61ee06e1d2ff12db8aac7a60e61286377232         - SHA256:1c54e2c305d7254cc3c3fb5cc5651064094e7cbff00e8f4a4e1932536864f240         - SHA1:eebbd844edee49449c7bdf6c1dc6243a85970544         - MD5Sum:c0fdedc4ecc16c0bce32d264006d74e2         - Checksum-FileSize:2832 ExpectedHash:  Err:1 http://archive.ubuntu.com/ubuntu xenial InRelease   Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) Fetched 2,832 B in 0s (4,827 B/s) Reading package lists... Done E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) E: Some index files failed to download. They have been ignored, or old ones used instead.   I have verified that   DNS is working correctly Tried Google DNS servers in /etc/resolv.conf /etc/network/interfaces has the correct values I am able to access http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease using wget -O- No firewall configured (iptable shows ALLOW for both IP4 and IP6) Tried disabling IPV6 on the server level $http_proxy is blank   Now I am completely at loss as to why am I getting Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)  What else can I try?
I can use my mobile broadband to access Internet with Firefox but when I want to install any package from terminal or make 'apt-get update' command I got the following error:  got 'NODATA' (does the network require authentication?)   apt-get update output:  Get:1 extras.ubuntu.com trusty InRelease [213 B] 98% [1 InRelease gpgv 213 B] [Connecting to archive.ubuntu.com] Splitting up /var/lib/apt/lists/partial/extras.ubuntu.com_ubuntu_dists_trusty_InRelease into data Ign extras.ubuntu.com trusty InRelease E: GPG error: extras.ubuntu.com trusty InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)    output of `cat /var/lib/apt/lists/partial/extras.ubuntu.com_ubuntu_dists_trusty_InRelease  &lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"&gt; &lt;html&gt; &lt;head&gt; &lt;title&gt;404&lt;/title&gt; &lt;meta http-equiv="Cache-Control" content="no-cache"/&gt; &lt;/head&gt; &lt;body&gt; &lt;p&gt; Not Found &lt;/p&gt; &lt;/body&gt; &lt;/html&gt;   output of wget:  wget -O - http://extras.ubuntu.com/ubuntu/dists/trusty/InRelease  --2014-06-01 09:23:35--  http://extras.ubuntu.com/ubuntu/dists/trusty/InRelease Resolving extras.ubuntu.com (extras.ubuntu.com)... 91.189.92.152 Connecting to extras.ubuntu.com (extras.ubuntu.com)|91.189.92.152|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 213 [text/html] Saving to: ‘STDOUT’   0% [                                       ] 0           --.-K/s              &lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"&gt; &lt;html&gt; &lt;head&gt; &lt;title&gt;404&lt;/title&gt; &lt;meta http-equiv="Cache-Control" content="no-cache"/&gt; &lt;/head&gt; &lt;body&gt; &lt;p&gt; Not Found  &lt;/p&gt; &lt;/body&gt; &lt;/html&gt;
Unable to mount ISO in write mode What should I do to avoid ear pain when flying? I always feel a pain in my ears when flying. Specially when descending. The last time I had extreme pain, feeling it inclusive around my eye balls. It felt like someone was touching the eye and pulling it from the inside. I really had to focus, close my eyes and hold to avoid screaming. I am not sure but I think both things might be related. Such a severe situation only happened once.  I just heard that with a cold the ear pain gets worse. I am bit worried that I might go through that situation again. I have a cold and I am going to fly soon.  What can I do to improve this?  I see that some consider this a duplicate of the question "best way to make my ears pop" but after reading the answers I think my question goes a bit beyond that since my pain is more extreme and I think it goes beyond just popping the ears. I also want to know if other methods, like using earplugs, might be effective. Too much whitespace in "Thanks for the feedback" While attempting to downvote something on a site I don't have an account on, I see this message, which has too much whitespace:    The same thing happens with upvotes (and プラス票が):    (I think it's safe to say that this is a network-wide bug, since I took these all on different sites.)  However, it looks more reasonable when you are not logged into the network at all (e.g. in private browsing):    An earlier version of this issue was reported at , but the difference is that there is no newsletter UI on the right anymore. (The extra space could have been justified before given the height of the newsletter; now it's definitely a bug.)  Also, is newsletter supposed to be gone? Simulate repeated rolls of a 7-sided die with a 6-sided die What is the most efficient way to simulate a 7-sided die with a 6-sided die? I've put some thought into it but I'm not sure I get somewhere specifically.  To create a 7-sided die we can use a rejection technique. 3-bits give uniform 1-8 and we need uniform 1-7 which means that we have to reject 1/8 i.e. 12.5% rejection probability.  To create $n * 7$-sided die rolls we need $\lceil log_2(  7^n ) \rceil$ bits. This means that our rejection probability is $p_r(n)=1-\frac{7^n}{2^{\lceil log_2(  7^n ) \rceil}}$.  It turns out that the rejection probability varies wildly but for $n=26$ we get $p_r(26) = 1 - \frac{7^{26}}{2^{\lceil log_2(7^{26}) \rceil}} = 1-\frac{7^{26}}{2^{73}} \approx 0.6\%$ rejection probability which is quite good. This means that we can generate with good odds 26 7-die rolls out of 73 bits.  Similarly, if we throw a fair die $n$ times we get number from $0...(6^n-1)$ which gives us $\lfloor log_2(6^{n}) \rfloor$ bits by rejecting everything which is above $2^{\lfloor log_2(6^{n}) \rfloor}$. Consequently the rejection probability is $p_r(n)=1-\frac{2^{\lfloor log_2(  6^{n} ) \rfloor}}{6^n}$.  Again this varies wildly but for $n = 53$, we get $p_r(53) = 1-\frac{2^{137}}{6^{53}} \approx 0.2\%$ which is excellent. As a result, we can roll the 6-face die 53 times and get ~137 bits.  This means that we get about $\frac{137}{53} * \frac{26}{73} = 0.9207$ 7-face die rolls out of 6-face die rolls which is close to the optimum $\frac{log 7}{log6} = 0.9208$.  Is there a way to get the optimum? Is there an way to find those $n$ numbers as above that minimize errors? Is there relevant theory I could have a look at?  P.S. Relevant python expressions:  min([ (i, round(1000*(1-(  7**i )  /  (2**ceil(log(7**i,2)))) )/10)  for i in xrange(1,100)], key=lambda x: x[1]) min([ (i, round(1000*(1- ((2**floor(log(6**i,2))) / (  6**i ))   )    )/10)  for i in xrange(1,100)], key=lambda x: x[1])   P.S.2 Thanks to @Erick Wong for helping me get the question right with his great comments.  Related question: Difference between JOIN and INNER JOIN Both these joins will give me the same results:  SELECT * FROM table JOIN otherTable ON table.ID = otherTable.FK   vs  SELECT * FROM table INNER JOIN otherTable ON table.ID = otherTable.FK   Is there any difference between the statements in performance or otherwise?   Does it differ between different SQL implementations? How do I show that $X = \left\{ (x,y) \in \mathbb{R}^2 \mid x \in \mathbb{Q}\text{ or }y \in \mathbb{Q}\right\}$ is path connected?    Note that $X$ is a topological space with subspace topology $\tau = \left\{ U \cap X \mid U\text{ is open in }\mathbb{R}^2\right\}$.  I only know two things (with respect to path connectedness):   A topological space $X$ is path connected iff for every $p,q \in X$, there is a continuous function $f: [a,b] \to X$ with $f(a)=p$ and $f(b) = q$.    Continuity $f$ is defined as for every open set in $X$, its preimage is open in $[a,b]$ (with subspace topology induced by $\mathbb{R}$ (with standard topology) )   Suppose $X$ and $Y$ are two topological spaces and $f: X \to Y$ is a continuous surjection. If $X$ is path connected, then $Y$ is path connected. Reference for the subgroup structure of $\rm{PSL}_2(q)$ I installed or upgraded to Ubuntu 16.04, but I'm having some problems with my graphics card.   The display is blank The display flickers Items on the screen do not display correctly Certain programs complain of graphics issues The computer boots to low-graphics mode Your specific issue may not be here, but try the solutions described in the answers anyway.   This question is very broad, but each one of these issues likely has one solution.    If you are experiencing a login loop, check the last part of my answer.    If you experience one of the listed issues and have your own solution (mine didn't work, or there's a faster way), feel free to post another POLITE answer, describing your problem and how you fixed it.    Those attempting to install Ubuntu, please refer to the section titled: If you are unable to enter a TTY or are trying to install Ubuntu. If $p$ is congruent to $2 \pmod 3$, how can I prove that all $a$, $1 \le a \le p-1$ are cubic residues $\mod p$?  Here's what I've done:  $1^3$ congruent to $1 \pmod p$ thus, 1 is a cubic residue, Also $(p-1)^3=(p-1) \pmod p$ implies  $$(p-1)^3 - (p-1) = (p-1)[(p-1)^2 -1] = (p-1)(p^2 -2p) = p(p-1)(p-2) $$ implies $$p|(p-1)^3 -(p-1)$$ Thus  $p-1$ is a cubic residue $\mod p$. Now I don't know how to show for $1\lt a \lt p-1$ are all cubic residues when $p$ is congruent to $2\pmod 3$. Why exactly is work a path function? This might be a stupid question, but why exactly is work a path function?  In school, my teacher said it’s because it depends on the path. She gave an example of walking up a mountain, and said the work you expend depends on the path you take (straight path up or circling up around the mountain). But isn’t the work expended just equal to $E= mgh?$ Removing intercept from GLM for multiple factorial predictors only works for first factor in model I am running a binomial logistic regression with a logit link function in R. My response is factorial [0/1] and I have two multilevel factorial predictors - let's call them $a$ and $b$ where $a$ has 4 factor levels  $(a_1,a_2,a_3,a_4)$ and $b$ has 9 factor levels $(b_1,b_2,\dotsc,b_9)$. Therefore:  mod &lt;- glm(y ~ a + b, family = binomial(logit), data=pretend) summary(mod)   The model output would then show all the information about the model as well as the coefficients.  There is a factor level for both a and b missing (a1 and b1) from the summary output. I understand that it is constrained in the "intercept" of the model. I have read that if I want to remove the intercept term and see the estimates for those factor levels I can just add -1 to the model formula, i.e.:  mod2 &lt;- glm(y ~ a + b - 1, family=binomial(logit), data=pretend) summary(mod2)   In the new model (mod2) the intercept term is then gone and variable a's factor-level a1 is given amongst the list of coefficients. But, variable b's factor-level b1 is still missing and given that there is no intercept term anymore, how can I interpret the odds-ratio for that factor level then?  Could someone please explain to me how to get the coefficient for b1 too and why this is happening? What's in a name: hyperparameters So in a normal distribution, we have two parameters: mean $\mu$ and variance $\sigma^2$. In the book Pattern Recognition and Machine Learning, there suddenly appears a hyperparameter $\lambda$ in the  regularization terms of the error function.  What are hyperparameters? Why are they named as such? And how are they intuitively different from parameters in general? Theorem. Let $X$ and $Y$ be sets with $X$ nonempty. Then (P) there exists an injection $f:X\rightarrow Y$ if and only if (Q) there exists a surjection $g:Y\rightarrow X$.  For the P $\implies$ Q part, I know you can get a surjection $Y\to X$ by mapping $y$ to $x$ if $y=f(x)$ for some $x\in X$ and mapping $y$ to some arbitrary $\alpha\in X$ if $y\in Y\setminus f(X)$. But I don't know about the Q $\implies$ P part.  Could someone give an elementary proof of the theorem? Reese's boyfriend seems to constantly be asleep. When I try and talk to him, she warns me that he's been hard at work all night, but I can't actually enter the shop at night.   Is there any way to talk to him or any benefit for doing so? I've tried to talk to him daily for a week (thinking it was something akin to talking to Sable) but I've had no luck. Trying to come in after-hours doesn't work. ,  and 1 still show the old bar. 1 See How to call the method correctly in Preference.OnPreferenceChangeListener() Do effects with the duration of one minute end at the beginning or the end of your turn? The Rage class feature of the Barbarian allows you to rage for one minute given you either took damage or attacked every round. A round is defined as a 6-second interval. So the rage can last up to 10 rounds. Now my question is, does it end at the end of your 10th round or at the beginning of your 11th round? There are other effects like that, also concentration spells with the duration of 1 or 10 minutes. Sometimes those are activated before combat starts and end during combat. In general: Does an effect/concentration end at the end of your last turn during the timespan or at the beginning of your first turn after the timespan? "State-of-the-art" and "technology" Prove that the expression cannot be a power of 2 Dynamically Determine Calling Context? We have various ways of invoking apex. Triggers, Inbound Webservices, @InvocableMethod,@RemoteAction and what not. Often we call some or other utility methods from these execution contexts. I have some generic utility method,that should behave differently from the context it is called?  I know about Trigger.isExecuting but it only tells if its running in trigger context or not.  I have a utility method that creates lead from Webservices, VF button click and via Lightning . Whenever we create a lead I want some special operations to be done via the source it was originated.(Its not just updating a simple field leadSource, I have some methods that creates some childs and update other records of other type) . I can achieve this by passing an extra parameter to utility method to tell about source, but i have then to edit hundred of other class that uses this utility method. If i could dynamically find out via which context this piece of code is running,then i would have to change only one class to satisfy my requirement.    Is there something in APEX that tells in what context the apex method was called?