command not found: sudo
Can sudo be reinstalled after being removed?
Non-ECC memory with ZFS: a stupid idea? I have a new server and am planning to upgrade the paltry 2 GB of memory to the maximum of 16 GB. (Theoretically 8 GB is the limit, but empirically 16 GB has been shown to work.)   advise that ECC memory is not that important, but I'm not so sure I believe this.     I've installed  and am planning to add ZFS volumes as soon as my new hard drives arrive.   Would it be stupid to skimp and get non-ECC memory for a ZFS-based NAS?  If it's necessary, then I'll bite the bullet, but if it's just paranoia, then I'll probably skip it.  Is there any reason ZFS or FeeeNAS specifically would require ECC memory, or suffer especially when running on a system using non-ECC memory? To be short, I want to copy a folder to a location /usr/share/screenlets/.... in Ubuntu 10.04 system. I tried by logging in as root from terminal giving su.   I even changed my user account type to ADMINISTRATOR; Yet, no use. PASTE option in the context menu's list in the folder /usr/share/... is INACTIVE.  How can I copy those files? Can the "Sacrifice (this card):" activated ability be placed back on the stack? This is a broad question so for simplicity I will use  and .  Scenario 1: Common exchange- creating a baseline.   Player A uses Naturalize on Seal of Fire  Player B Sacrifices SoF in response. SoF is highest on the stack and goes off first.  This leaves Naturalize without a valid target.   Scenario 2: Complicated exchange- Is this legal?   Player B Sacrifices SoF. In response Player A targets it with Naturalize. SoF is on the stack and it's ability has not resolved. Player B (as above) sacrifices SoF in response to the Naturalize.    Can Seal of Fire be placed back on the stack by re-activating its ability, potentially with a new target? Why does this excerpt say that unbiased estimation of standard deviation usually isn't relevant? Why is variance squared? How to move windows that open up offscreen? I have a dual monitor setup, and I recently played around with the positioning settings, and some of my single window applications do the favour of preserving where they were last closed, and opening in the same position later. Unfortunately, that now places them out of the viewable area of my screens!  Is there some way to force a particular window into the viewable area? Get a list of dates between two dates Using standard mysql functions is there a way to write a query that will return a list of days between two dates.  eg given 2009-01-01 and 2009-01-13 it would return a one column table with the values:   2009-01-01   2009-01-02   2009-01-03  2009-01-04   2009-01-05  2009-01-06  2009-01-07  2009-01-08   2009-01-09  2009-01-10  2009-01-11  2009-01-12  2009-01-13   Edit: It appears I have not been clear. I want to GENERATE this list. I have values stored in the database (by datetime) but want them to be aggregated on a left outer join to a list of dates as above (I am expecting null from the right side of some of this join for some days and will handle this). Plot $|z - i| + |z + i| = 16$ on the complex plane Is $0 \, \mathrm m = 0 \, \mathrm s = 0 \,\mathrm {kg} = 0$? How do we define $[0 \, \mathrm m]$?  I once was given an assignment where I was asked to deduce and write down some physical quantity. It turned out that this quantity was $0$ in one unit or another, so I decided to drop the physical units because I figured that it didn't matter anyhow.  But I got to thinking:  If $0 \, \mathrm m = 0$, then we could add units of different dimensions (an operation not normally defined) like so: $5 + 0 \,\mathrm m = 5$.   Does $[ \cdot ]$ map $0 \, \mathrm m$ to both $0$ and $L$? Is there an established regime of thinking about physical quantities as an abstract algebra? Perhaps as a vector space where formal sums such as $5 \, \mathrm m + 10 \, \mathrm s$ are allowed? Would it be improper to drop the units of measurement of $0 \,\mathrm m$ like this in an academic paper? In a particular textbook, the work function of a metal (in the context of the photoelectric effect) is defined as:     the minimum amount of energy necessary to remove a free electron from the surface of the metal   This sounds similar to ionisation energy, which is:     the amount of energy required to remove an electron from an atom or molecule in the gaseous state   These two energies are generally different. For instance, Copper has a work function of about 4.7eV but has a higher ionisation energy of about 746kJ mol-1 or 7.7eV.  I've sort of figured it's because the work function deals with free electrons whilst ionisation is done with a valence electron still bound within the atom. Is the difference due to the energy required to overcome the attraction of the positive nucleus? Newton's 3rd law... hitting drywall (which I break) vs hitting a brick (which breaks me)? According to the Third Newton's law of motion:        For every action there is an equal and opposite reaction.   So, I understand that if I hit a brick wall with $50\, \mathrm{lbs}$ of force, the brick wall also hits me with $50\, \mathrm{lbs}$ of force (usually painfully). In this instance, Newton's third law makes sense. What I'm confused about is, if I hit a patch of drywall with $50\, \mathrm{lbs}$ of force, it's probably going to break, and due to the lack of pain in my hand, I can tell it did not hit me back with $50\, \mathrm{lbs}$ of force.   How does Newton's third law apply to situations when one object or the other is destroyed? It certainly seems like at that point it is incapable of delivering the full force of my blow back to me. What happens with the energy? Infinite Series Convergence Verification I'm currently tackling the following infinite series in order to determine if it converges or not:  $$\sum_{n=1}^\infty \frac{\sqrt{n+1}-\sqrt{n}}{n}$$  What I've done is rearranged this to make use of the comparison test, shown below:  $$= \frac{\sqrt{n+1}-\sqrt{n}}{n} * (\frac{\sqrt{n+1}+\sqrt{n}}{\sqrt{n+1}+\sqrt{n}})$$  $$= \frac{(n+1)-(n)}{n(\sqrt{n+1}+\sqrt{n})}$$  $$= \frac{1}{n(\sqrt{n+1}+\sqrt{n})}$$  $$= \frac{1}{n^{3/2}+\sqrt{n+1}} &lt; \frac{1}{\sqrt{n+1}} &lt; \frac{1}{\sqrt{n}} $$  However, $\frac{1}{n}$ is smaller than $\frac{1}{\sqrt{n}}$, therefore:  $$  \frac{1}{n}   &lt; \frac{1}{\sqrt{n}}$$   This implies divergence by the comparison test due to the fact $\frac{1}{n}$ diverges, and if a smaller series diverges any larger series must as well.  Is this right? If I've made any mistakes in any part, please tell me! I have a bathroom door that is quite loud when operated. And when someone goes to the bathroom at night, it innevatibly wakes someone up (and baby room is just across from the bathroom!) there are 3 components of noise, and I was wondering if there is an alternative to fixing them:   door bangs against the jamb (this is fixed with simple foam bumpers) latch mechanism makes a loud CLUNK when door is pushed closed (I was able to dampen it just a bit by putting foam inside strike plate, but it is still quite loud) lock button also makes a CLUNK when the knob is turned and it is released (this can be battled by replacing with a mechanism that needs to be manually opened [twist instead of push] but it is less convenient, and I would prefer something that automatically unlocks)   Any suggestions as to a knob that has a dampening of the latch and lock button? I have only found one youtube video of my ideal handle, but there is no information on how it works, where to buy it, or anything else: Let $E$ be measurable and define $f:E\rightarrow\mathbb{R}$ such that $\{x\in E : f(x)&gt;c\}$ is measurable for all $c\in\mathbb{Q}$, is $f$ measurable?  There are a number of equivalent definitions for the measurability of a function and the most obvious one would be to show that $\{x\in E : f(x)&gt;c\}$ is measurable for all $c\in\mathbb{R}$.  Thus my strategy has been to consider an arbitrary irrational $y$ and use the density of the rationals in the reals to show that there exists some open set $O$ such that $m^*(O-\{x\in E : f(x)&gt;y\})&lt; \varepsilon$.  I would do this by choosing some rational $q&lt;y$, close enough to $y$, such that the set of values in $E$ which get sent under $f$ to values strictly greater than $q$ and less than or equal to $y$ is small enough.  But that doesn't in general seem possible since I could keep sending intervals of some fixed positive length to smaller and smaller regions just beneath $y$.  However conversely, such a function would not be enough for a counter example, since finding such a function only rules out this strategy, but doesn't necessarily entail non-measurability.  Is there a better definition of the measurability of a set I should use? or does the statement actually not imply measurability?  Thanks. How to pluralize an acronym which ends in 'S' correctly? When using the acronym package, how can you  an acronym which ends on 'S'?  Take the acronym: OS - operating system  It should be pluralized as OS's, but is pluralized as OSs when using \acp. I must be missing something with regards to setting up PostgreSQL. What I'd like to do is create multiple databases and users that are isolated from each other so that a specific user only has access to the databases I specify. However, from what I can determine, any created user has access to all databases without any specific grants being given.  Here is what I do on an Ubuntu Server 12.04:   apt-get install postgresql sudo -u postgres createuser -DRSP mike1 (Specifying the password for the new user) sudo -u postgres createdb data1 psql -h localhost -U mike1 data1 (Specifying the password for the user mike1 to login)   It seems that new user "mike1" has no problem connecting to database "data1" and creating tables etc. And this without running any GRANT command at all (and the owner of "data1" is "postgres" since I didn't specify an owner in step 3). Is this really how it is supposed to work?  What I'd like to do is grant mike1 full access to data1 and then repeat this for more users and databases, making sure that the users only have access to one (or possibly several) databases of my choice. How to detect the Internet connection is offline in JavaScript? What commands are there for horizontal spacing? I know that \: in LaTeX produces a space when rendered.  Are there any alternatives, because my LaTeX renderer doesn't support \: (it renders it as text), and there is no help / FAQ that I can find. Compute the mean of $(1 + X)^{-1}$ where $X$ is Poisson$(\lambda)$ Question  Let $X$ be Poisson with parameter $\lambda$.  Compute the mean of $(1 + X)^{-1}$. (Introduction to Probability Theory, Hoel, pp. 104)  Answer Key  The answer key shows that the mean is $\lambda^{-1}(1 - e^{-\lambda})$  My Solution  $$E(1 + X)^{-1} = \sum\limits_{j = 1}^\infty (1 + j)^{-1} \dfrac{\lambda^{(1 + j)^{-1}}e^{-\lambda}}{(1 + j)^{-1}!}$$ $$= e^{-\lambda} \sum\limits_{j = 1}^\infty \dfrac{\lambda^{(1 + j)^{-1}}}{((1 + j)^{-1} - 1)!}$$ $$= \lambda^{-1} e^{-\lambda} \sum\limits_{j = 1}^\infty \dfrac{\lambda^{(1 + j)^{-1} - 1}}{((1 + j)^{-1} - 1)!}$$ $$= \lambda^{-1} e^{-\lambda}(e^{\lambda} - 1)$$ $$= \lambda^{-1}(1 - e^{-\lambda})$$  EDIT: I found why I got the answer incorrect.  Thanks for those who answer the question! :) Is it possible to set an SSLProtocol in Apache for a single VirtualHost (poodle)? I'm trying to test a patch for the  that involves disabling SSLv3 on my web server. In order to test this on a non-production environment first, I'm setting the SSLProtocol on a VirtualHost for a different test server. My config looks something like this:  &lt;VirtualHost *:443&gt;     SSLEngine On     SSLProtocol All -SSLv2 -SSLv3     ServerName test.mysite.com     # bunch of other stuff omitted &lt;/VirtualHost&gt;   However even after restarting apache my test site is still claimed to be vulnerable. Is this expected to work? I'm wondering if I have to set it in the global ssl config or whether there's something else subtle that's causing the setting not to take and/or work.