I'm trying to use the makemap hash command, but even as root it says Permission denied. Command i'm trying to run:  sudo makemap hash /etc/mail/authinfo/gmail-auth &lt; /etc/mail/authinfo/gmail-auth -bash: /etc/mail/authinfo/gmail-auth: Permission denied
Disclaimer: I'm pretty novice at sysadmin stuff.  I'm trying to set up port forwarding in an AWS EC2 instance, this has to be done in the command-line because I don't want to go in and edit anything, it has to be automatic (it's part of a build process).   sudo echo "net.ipv4.ip_forward = 1" &gt;&gt; /etc/sysctl.conf      Permission denied   The weird thing is I've been (successfully) using sudo for pretty much every command that required su privileges. If I do sudo su before the command (trying it out by hand in an ssh session), then it works.  Reasons behind this? Possible solutions that don't involve sudo su or manual edits?
is it problematic to cluster across two datacenters w/aag? In general is it problematic to cluster across two datacenters that are up to 15-miles apart?  For this one particular project the approach is the following?   2-Node Failover Cluster across two datacenters, one node per datacenter local SAN disks, no shared disks 'Node and FileShare Majority' at third location on-campus employ AAG, failover will be manual; asynchronous mode   Is anyone implementing something like this with success??!?  Thanks so much for the help!! Finding a formula to sum natural numbers up to $n$ Possible Duplicate:          I got this question in homework:  Find an expression for the sum ‫‪     $\sum k = 1 +\cdots + n‬‬$.    and prove it using an induction.   I'm not even near finding the expression. What I did notice is that if $n$ is (for example) 5 then the sum would be   $5^2 - 4^2 + 3^2 - 2^2 + 1^2$  So the first number is always positive and from there on the sign changes.  Any tips on how do I contintue from this point on, assuming I'm in the right direction?  Thanks! Vote for Tag Synonyms Directly on the Page Spelling or grammar error? I'm writing a php program that pulls from a database source. Some of the varchars have quotes that are displaying as black diamonds with a question mark in them (�, , I assume from Microsoft Word text).  How can I use php to strip these characters out? "Answerer" and "asker" Number of possible permutations of n1 1's, n2 2's, n3 3's, n4 4's such that no two adjacent elements are same? Tools for automating document compilation A lot of people write makefiles that say something like  paper.pdf: paper.tex         pdflatex paper         bibtex paper         pdflatex paper         pdflatex paper   To handle re-running TeX to get new/changed references and so forth. Is there a better way to do this? My boot is horribly slow, and I don't know why.  $ systemd-analyze  Startup finished in 10.975s (kernel) + 49.732s (userspace) = 1min 708ms $ systemd-analyze blame           34.971s apt-daily.service          20.590s snapd.refresh.service          17.113s grub-common.service          16.033s apport.service          16.027s networking.service          15.894s ondemand.service          15.860s irqbalance.service          15.655s speech-dispatcher.service          11.695s ModemManager.service           9.772s accounts-daemon.service           8.626s NetworkManager-wait-online.service           8.058s systemd-logind.service           8.053s bluetooth.service           7.944s gpu-manager.service           7.896s alsa-restore.service           7.892s pppd-dns.service           7.882s rsyslog.service           7.860s avahi-daemon.service           7.844s dev-sda1.device           7.842s systemd-user-sessions.service           7.648s lightdm.service           7.610s teamviewerd.service           6.445s apparmor.service   Also, during boot-up, I see a message that says something like:  device descriptor read/all, error -62 ata1 softreset failed (device not ready) #most of the times error loading journal #(sometimes) Test WP failed, assume Write Enabled Asking for cache data failed     #most of the times Assuming drive cache: write through   apt-daily.service slows the boot the most. Any idea on how to tackle that?  I have Ubuntu MATE 16.04. Why is torque a cross product? If I'm not wrong, torque is perpendicular to both the radius and force i. e. It is along the axis of rotation. Questions that arise are- why do we consider the length between the axis/point of rotation while calculating torque? More importantly why is torque a cross product? Installing node with apt-get or downloading the Linux Binaries (.tar.gz) What is the difference between installing node.js with 'sudo apt-get install nodejs' or downloading the Linux Binaries (.tar.gz) and following  instructions?  Is the outcome the same? LED as power generator String concatenation: concat() vs "+" operator Assuming String a and b:  a += b a = a.concat(b)   Under the hood, are they the same thing?  Here is concat decompiled as reference. I'd like to be able to decompile the + operator as well to see what that does.  public String concat(String s) {      int i = s.length();     if (i == 0) {         return this;     }     else {         char ac[] = new char[count + i];         getChars(0, count, ac, 0);         s.getChars(0, i, ac, count);         return new String(0, count + i, ac);     } } bash command for each file in a folder I have a set of files on which I would like to apply the same command and the output should contain the same name as the processed file but with a different extension.  Currently I am doing rename /my/data/Andrew.doc to /my/data/Andrew.txt I would like to do this for all the .doc files from the /my/data/ folder and to preserve the name.  I tried several versions but I guess I have something wrong in the syntax as I an new to linux. Rice with worm and possibly their eggs I bought a bag of brown rice from a store. After having opened and used for a while, I found there were moths flying in the house. At the same time, I found worms in the rice. I suspect that the moths are from the worms(rice-size, white body, dark head). I guess but am not sure if they are called rice moths. There were also many little sand-like things in the rice bag, are they the eggs of the rice moths?  Will eating this infested rice pose a health risk? How do I make a floor plan with specific dimensions? This is my very first time of using blender. I've tried several tutorials but can't find anything that tells me how to do the very basic thing i want to do.  I simply want to draw a floor plan for a room which is 13 feet by 11 feet and make it 3d so that ultimately i can play with where things go in that room.  Can anyone take me through the steps needed to do this?   I will be so grateful.  Thank you in advance What are the differences between "su", "sudo -s", "sudo -i", "sudo su"? I already read it from manual but I can't see difference..  su - change user ID or become superuser  sudo -s [command]   The -s (shell) option runs the shell specified by the SHELL environment variable if it is set or the shell as specified in passwd(5).  If a                    command is specified, it is passed to the shell for execution.  Otherwise, an interactive shell is executed.  sudo -i disappear description in manual Is there a single word which means "a person, and all of his ancestors", or "a person, and all of his descendants"? There are a lot of words describing ancestral relationships between people, such as:  parent grandparent great-grandparent any of the above can be described as an "ancestor".  child grandchild great-grandchild any of the above can be described as a "descendant".   I am wondering if there are single words (nouns) which describe any of the following concepts:  A person and all of his/her ancestors A person or any of his/her ancestors A person and all of his/her descendants A person or any of his/her descendants   Any ideas? Why is negative times negative = positive? Someone recently asked me why a negative $\times$ a negative is positive, and why a negative $\times$ a positive is negative, etc.  I went ahead and gave them a proof by contradiction like so:  Assume $(-x) \cdot (-y) = -xy$  Then divide both sides by $(-x)$ and you get $(-y) = y$  Since we have a contradiction, then our first assumption must be incorrect.  I'm guessing I did something wrong here. Since the conclusion of $(-x) \cdot (-y) = (xy)$ is hard to derive from what I wrote.  Is there a better way to explain this?  Is my proof incorrect?  Also, what would be an intuitive way to explain the negation concept, if there is one? How to understand the definition of vector and tensor? Physics texts like to define vector as something that transform like a vector and tensor as something that transform like a tensor, which is different from the definition in math books. I am having difficulty understanding this kind of definition. To me, it goes like this:   First we have a collection of bases or coordinate systems (do these represent reference frames?) and the transformations between them. A vector/tensor is an assignment of an array of numbers to each basis, and these arrays are related to each other by coordinate transformations.   I am wondering how coordinate systems and transformations are specified.    Do we need all possible coordinate systems and transformations to define a vector space or just a few of them? How to define the concept of basis and coordinate transformation without completing the very notion of vector?