Bind to ports less than 1024 without root access I would like to run applications I'm working on that binds to port numbers less than 1000 without requiring root access.   I'm using Linux Mint and have root access to set it up. I would ideally like to be able to do it over SSH.  Also happy hear if it isn't possible or I shouldn't be doing it, if that is the case.  EDIT: Mostly I'm happy to use higher port numbers for development, but Flash is expecting a socket policy on port 843. Currently I have to run the app as root and therefore I can't run it from my Makefile which is a PITA.
How to run a server on port 80 as a normal user on Linux? I have Googled about a solution for quite some time, but couldn't find an answer.   I am on Ubuntu Linux and want to run a server on port 80, but due to security mechanism of Ubuntu, I get the following error:      java.net.BindException: Permission denied:80   I think it should be simple enough to either disable this security mechanism so that port 80 is available to all users or to assign required privileges to the current user to access port 80.
When is the move constructor called in the `std::move()` function? Algorithm for minimization of sum of squares in regression packages I accidentally killed the orphanage lady before I started the quest. She just pissed me off, sadly it will not acknowledge that I have finished the quest and I haven't been contacted. Is there another way to join the Dark Brotherhood? I think the term "back and forth" gets thrown around a lot without much thought.  From Dictionary.com:         [fawrth, fohrth]      adverb    1.  onward or outward in place or space; forward: to come forth; go forth.   Wouldn't the term be more meaningful if "forth" was used first since you have to have a starting place before you can go "back"?  Examples:        I've been going back and forth from Houston to New York.   I've been going forth and back from Houston to New York.      Which is more correct? Multiple workspaces on Ubuntu 18.04.1 LTS and later with GNOME Shell Thermodynamics of supercooled water Now that it's been freezing outside for the last few days, I experimented a bit with supercooling. I've left a bottle of clean water outside for a few hours, and behold, when I shook the bottle, the liquid began to freeze rapidly, as expected.   However, not all of the water froze, only about half of it. This got me thinking.  I reasoned that happens because freezing releases heat, and that heat raises the temperature of the ice and remaning water to 0$^\circ$C, at which point the freezing stops.  To try to quantify this, set   $H_f = 334000 \frac{J}{kg}$, the "freezing heat" (enthalpy of fusion) of ice, $c_i = 2110 \frac{J}{kg\cdot K}$, specific heat of ice, $c_w = 4181 \frac{J}{kg\cdot K}$, specific heat of water, $M$, initial mass of supercooled water, $T_0$, initial temperature of supercooled water, $m$, mass of ice at a given moment, $T$, temperature at a given moment.   We suppose that the energy released by the freezing of a $\textrm dm$ mass of ice is used up by raising the temperature of both the already frozen ice ($m$) and the remaining water ($M-m$):  $$ \textrm dm \cdot H_f = c_i m \cdot\textrm dT + (M-m)c_w \cdot\textrm dT$$  By rearranging we get a linear differential equation for $m(T)$:  $$\frac{\textrm dm}{\textrm dT}+\frac{c_w-c_i}{H_f}m = \frac{c_w}{H_f}M$$  The solution of this equation, using the initial condition that at $T=T_0$, $m=0$:  $$ m = M \frac{c_w}{c_w-c_i}\left[ 1-e^{-\frac{c_w-c_i}{H_f}(T-T_0)} \right]$$  This looks neat, however, plugging in the actual values of the constants, $T = 0^\circ$C and $T_0 = -6^\circ$C, I get that little more than 7% of the water should freeze - as opposed to more than half, as I've observed. What's worse, the formula can be used to calculate the starting temperature required to freeze all the supercooled water: $$T_{all} = \frac{H_f \log\frac{c_w}{c_i}}{c_i-c_w}=-110.26^\circ \textrm C$$ which seems absurd.  Where is the error in the calculation above?  I've made a number of assumptions which may or may not hold:   the constants are really constant. I think this is a good approximation for $c_w$, a not that good but still acceptable approximation for $c_i$, and I suppose it holds to $H_f$ to some extent as well. there is no heat transfer with the environment, i.e. the bottle is a closed system. The process seemed fast enough (a few seconds at most) for this to be a good approximation. the system is in a thermal equilibrium at all times and the heat released by the freezing of the ice is distributed evenly in the emerging ice-water mixture. Now this is where I have doubts. Precisely because of the process happening so fast, this might not be true at all. However, acknowledging the presence of temperature variations makes the problem order of magnitudes harder: one has to solve a system of partial differential equations that take heat transfer, the shape of the bottle and \$deity knows what else into account. How to change envelope from address using PHP mail? Proof of convergence of sequences Problem: Show that if $x_n\to 5$ then $\dfrac{x_n +1}{\sqrt{x_n -1}} \to 3$.  So I know $|x-5|&lt;\epsilon$ and I need to show that $\left|\dfrac{x_n +1}{\sqrt{x_n -1}} -3\right| &lt; \epsilon$.  I tried applying the triangle inequality (and a bit of algebra) to get $$\left|\frac{x_n +1}{\sqrt{x_n -1}} -3\right| \leq |x_n -5| \left |\frac{1}{\sqrt{x_n -1}}\right| + \left|\frac{6}{\sqrt{x_n-1}} -3\right|.$$  From this I know that $|x_n -5| &lt;\epsilon$ and can show that $\left |\dfrac{1}{\sqrt{x_n -1}}\right|&lt;1$. So my only problem is the second part of the sum. I have no idea what to do with it to get everything to be less than $\epsilon$. The topic which haunted me for two years until I gave up on it. But now I am doing engineering and this topic suddenly popped out of my textbook from nowhere. I seriously need to understand this topic because I wasn't able to do so in the past. I have read many book on 'energy' and it came to nothing. Maybe just because the many books I have read all said 'energy' is something which doesn't 'exist'! It is 'abstract'! It is just a number which represents the state or orientation of a system. But then I see so many examples that 'uses' energy to do 'work'. But the question here is that if anything doesn't exist in this universe, then how can the same thing be used to do something that exist?  My problem is that I didn't understood the topic 'energy' and all the other topics related to it (work, power etc.) Meaning of Sun Lamp Size? In Cycles, a sun lamp is treated as infinitely far away - only the angle matters, not the position. Other lamps have their sizes defined in blender units: a point lamp with size 1 emits light from a area with size of 1. But if a sun lamp at infinity had a size of 1 blender unit, the angular arc of that sun would be nonexistent.  Clearly, when you change the size of a sun lamp, shadows get fuzzier or sharper. But what does that actually mean? What are you changing? I've known that one can arrange all the numbers from $1$ to $\color{red}{15}$ in a row such that the sum of every two adjacent numbers is a perfect square. $$8,1,15,10,6,3,13,12,4,5,11,14,2,7,9$$ Also, a few days ago, a friend of mine taught me that one can arrange all the numbers from $1$ to $\color{red}{305}$ in a row such that the sum of every two adjacent numbers is a perfect cube. $$256,87,129, 214, 298, 45, 171, 172, 44, 299, 213, 130, 86, 257, 255,$$ $$88, 128, 215, 297, 46, 170, 173, 43, 300, 212, 131, 85, 258, 254, 89, 127, 216, 296,$$ $$ 47, 169, 174, 42, 301, 211, 132, 84, 259, 253, 90, 126, 217, 295, 48, 168, 175, 41, 302, $$ $$210, 133, 83, 260, 252, 91, 125, 218, 294, 49, 167, 176, 40, 303, 209, 134, 82, 261, 251,$$ $$ 92, 33, 183, 160, 56, 287, 225, 118, 98, 245, 267, 76, 140, 203, 13, 14, 202, 141, 75, 268,$$ $$ 244, 99, 26, 190, 153, 63, 280, 232, 111, 105, 238, 274, 69, 147, 196, 20, 7, 1, 124, 219,$$ $$ 293, 50, 166, 177, 39, 304, 208, 135, 81, 262, 250, 93, 32, 184, 159, 57, 286, 226, 117, 8,$$ $$ 19, 197, 146, 70, 273, 239, 104, 112, 231, 281, 62, 154, 189, 27, 37, 179, 164, 52, 291, 221,$$ $$ 122, 3, 5, 22, 194, 149, 67, 276, 236, 107, 109, 234, 278, 65, 151, 192, 24, 101, 242, 270,$$ $$ 73, 143, 200, 16, 11, 205, 138, 78, 265, 247, 96, 120, 223, 289, 54, 162, 181, 35, 29, 187,$$ $$156, 60, 283, 229, 114, 102, 241, 271, 72, 144, 199, 17, 108, 235, 277, 66, 150, 193, 23,$$ $$ 4, 121, 222, 290, 53, 163, 180, 36, 28, 188, 155, 61, 282, 230, 113, 103, 240, 272, 71, 145,$$ $$ 198, 18, 9, 116, 227, 285, 58, 158, 185, 31, 94, 249, 263, 80, 136, 207, 305, 38, 178, 165,$$ $$ 51, 292, 220, 123, 2, 6, 21, 195, 148, 68, 275, 237, 106, 110, 233, 279, 64, 152, 191, 25,$$ $$100, 243, 269, 74, 142, 201, 15, 12, 204, 139, 77, 266, 246, 97, 119, 224, 288, 55, 161,$$ $$ 182, 34, 30, 186, 157, 59, 284, 228, 115, 10, 206, 137, 79, 264, 248, 95$$ Here, I have a question.  Question : Does there exist at least one positive integer $n\ge 2$ satisfying the following condition for each $N\ge 2\in\mathbb N$? Condition : One can arrange all the numbers from $1$ to $n$ in a row such that the sum of every two adjacent numbers is of the form $m^N$ for some $m\in\mathbb N$.  Added : I crossposted to . Prove that inequality is true for $x>0$: $(e^x-1)\ln(1+x) > x^2$ Is there an exception to the prohibition against ending a sentence with “ ’s ” at work here? The ’s can be used as a contraction representing a weak, unstressed word that is not pronounced.  It allegedly cannot occur in sentence final position.        She is not ready, but he is.   She’s not ready, but he is.   She’s not ready, but *he’s.      The last one is not grammatical there.  Similarly, here the last one is not grammatical:        He has not started yet, but she has.   He’s not started yet, but she has.   He’s not started yet, but *she’s.       claims this is because you cannot end a sentence with a weak form.  It backs up its point with reasonably scholarly documentation.  However, this does not seem to be invariably true.        Shall we go to the movies?  Yes, let us go.   Shall we go to the movies?  Yes, let’s go.   Shall we go to the movies?  Yes, let’s.      Unlike the third example in the first two sets, here in this case the third example is indeed grammatical, despite ending with a weak form.  Is this an exception to the rule, or is there another rule at work here? Why is this sentence correct? “She suggested that he go to the cinema.” present continous or present perfect continous? Should I write 'I have been reading a book now' or 'I am reading a book now'? I started to read one week ago and I haven't ended yet. Thanks for help In  answer to the question "why does the moon have the same rotation and revolution periods?", we read:     The mass and speed of rotation of the Earth influence the moon in that some of its rotational energy is actually transferred to the moon. (...) Many of the moons in the solar system have also reached this point of equilibrium. In Jupiter, the moons Amalthea, Thebe, Io, Ganymede, Callista, and Europa, all have identical rotational and revolutionary periods.    My two questions are:   Can we show the mechanics of this quantitatively?  Does the system Earth-Sun experience the same phenomenon, in some measure? Will then the earth slow down its rotation speed until it will show always the same face to the sunlight? In this last case, on which timescale? How to apply a macro to each column of a table I'm on a new computer and I haven't downloaded Data Loader in years but now, I'm having all kinds if issues.  So apparently, I have to download Zulu JDK 11 (msi) first, Then download and unzip Data Loaded and install. Which opens a command prompt... After I follow all of the command prompt steps, then I get an error.  Am I supposed to install Java too? And if so, do I download Java or Zulu first?  Apparently a lot of people are having this same problem with no resolve.  Any help would be much appreciated. Why isn't apt full-upgrade getting an updated software key signature for skype After a recent apt update &amp;&amp; apt full-upgrade I started getting the following error when running apt full-upgrade subsequently: Get:4 https://repo.skype.com/deb stable InRelease [4,502 B]                                         Err:4 https://repo.skype.com/deb stable InRelease   The following signatures were invalid: EXPKEYSIG 1F3045A5DF7587C3 Skype Linux Client Repository &lt;se-um@microsoft.com&gt; W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://repo.skype.com/deb stable InRelease: The following signatures were invalid: EXPKEYSIG 1F3045A5DF7587C3 Skype Linux Client Repository &lt;se-um@microsoft.com&gt; W: Failed to fetch https://repo.skype.com/deb/dists/stable/InRelease  The following signatures were invalid: EXPKEYSIG 1F3045A5DF7587C3 Skype Linux Client Repository &lt;se-um@microsoft.com&gt; W: Some index files failed to download. They have been ignored, or old ones used instead.  Is there a way to correct this, or is it down to Microsoft/Canonical to produce/update the necessary key signatures? Show that if the Riesz map is surjective on $H$, then $H$ is a Hilbert space Let $H$ be a vector space equipped with an inner product $(\cdot, \cdot)$ and $f:H\to H',\ f(x)=(\cdot,x)$ surjective. Now, why $H$  is a Hilbert space? The other direction is clear by Riesz' representation theorem but what about this?