security - is this my public key? my private key? or the keys of the program I'm using? I asked a recent, separate Ask Ubuntu question with the following in the body:  W: An error occurred during the signature verification.  The repository is not updated and the previous index files will be used.  GPG error: https://dl.winehq.org/wine-builds/ubuntu bionic InRelease:  The following signatures couldn't be verified  because the public key is not available: NO_PUBKEY 76F1A20FF987672F   As you can see part of my error message exposes PUBKEY 76F1A20FF987672F. Was this the public key of WINE, or is this my own public key?  Most importantly, is this PUBKEY 76F1A20FF987672F information I should NOT be posting on a public forum (this one)?  I assume a private key is the only thing I would never want to divulge. I'm reading  page now, but it's a little overwhelming.
How do I fix the GPG error "NO_PUBKEY"? I added some extra repositories with the Software Sources program. But when I reload the package database, I get an error like the following:     W: GPG error:  trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8BAF9A6F   I know I can fix it using apt-key in a terminal, according to the official Ubuntu documentation. But I would have liked to do it graphically. Is there a way to do this without using a terminal?
I know that matrix multiplication in general is not commutative. So, in general:  $A, B \in \mathbb{R}^{n \times n}: A \cdot B \neq B \cdot A$  But for some matrices, this equations holds, e.g. A = Identity or A = Null-matrix $\forall B \in \mathbb{R}^{n \times n}$.  I think I remember that a group of special matrices (was it $O(n)$, the ?) exist, for which matrix multiplication is commutative.  For which matrices $A, B \in \mathbb{R}^{n \times n}$ is $A\cdot B = B \cdot A$? how to bring up the menu at the bottom left hello everyone I have a little problem, how do I bring up the menu in the circle? when I select another object the menu becomes non-existent How do I stop Windows 10 from updating my graphics driver? Counting the number of propagating degrees of freedom in Lorenz Gauge Electrodynamics When you search on any of the SE network sites, with a tag (so that a description is shown); it shows the tag info content box, with the highlight-search-term span elements.  For eg. 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I then imported it into Unreal Engine 4 and it didn't import any textures; I clicked the Upload Textures option in Unreal Engine.  Is there something I'm doing wrong or is it Blender? Below is an example from I.N. Herstein:       Let  $R=\Bigg\{\left( \begin{array}{ccc} a &amp; b \\ -b &amp; a \end{array} \right)\Bigg|a,b\in \mathbb R\Bigg\}$ and let $\mathbb C$ be the field of complex numbers. Define $\psi :R\to \mathbb C$ by $\psi\left( \begin{array}{ccc} a &amp; b \\ -b &amp; a \end{array} \right)=a+bi.$       It is asked to prove that $\psi$ is a ring isomorphism of $R$ onto $\mathbb C$ .    can anyone help me with some hint how to prove the ring isomorphism. Disable sleep on laptop lid close in tty1 I'm using Ubuntu Desktop 15.10 on a laptop and it runs an Apache server with SSH as well. When using a GUI, I have the power options set to not sleep at all even when the laptop lid is closed, but recently I stopped the X-System and am now using TTY1 instead to save resources. However, in TTY1, if I close the laptop lid, the computer goes to sleep and prevents the SSH and Apache server from working. Any way to prevent this easily? The realistic answer I bet is to use Ubuntu Server instead (unless I'm mistaken and Ubuntu Server will also sleep on lid close) but I don't exactly want to switch yet unless there's an easy way to switch to it like you can switch from ubuntu-desktop to lubuntu-desktop? Any advice is welcome to prevent the computer from sleeping What's the protocol for requesting a tag warning? On a particular site, RPG Stack Exchange, we've decided on our meta on a couple of tags that should have tag warnings, and on what those tag warnings should say. I am  on the site in question.  What should we do to get the tag warnings implemented? Do we do any/all of the following?:   start a [feature-request] on our meta for the tag warnings? raise a CM escalation? contact staff via the contact form? ping a staff member in the Teacher's Lounge? anything else? Moving users folder on Windows Vista/7 to another partition When I format the computer and reinstall Windows, my first step is move the My Documents folder to another partition. In Windows XP it wasn't enough because the desktop folder and another user folders was in the primary partition.  Now in Windows Vista and 7 we can use junctions/symlinks to "move" the folder to another partition and Windows and another programs will think that the data is in the primary partition.  What the fastest and secure steps to move the Users folder to another partition and to create the hardlinks correctly? What we've gelost — why doesn't English use the prefix "ge-"? 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What's the best way to break from nested loops in Javascript?  //Write the links to the page. for (var x = 0; x &lt; Args.length; x++) {    for (var Heading in Navigation.Headings)    {       for (var Item in Navigation.Headings[Heading])       {          if (Args[x] == Navigation.Headings[Heading][Item].Name)          {             document.write("&lt;a href=\""                 + Navigation.Headings[Heading][Item].URL + "\"&gt;"                 + Navigation.Headings[Heading][Item].Name + "&lt;/a&gt; : ");             break; // &lt;---HERE, I need to break out of two loops.          }       }    } } How can I easily encrypt a file?