Can't do anything with APT
dpkg error: "trying to overwrite file, which is also in..."
A new version of Ubuntu has been released. I still can't find it on ubuntu.com. Where can it be downloaded from, or is it the only way to install it using update-manager to upgrade an existing installation? Multiple runnable classes inside JAR, how to run them? Traveling to the US with new passport, visa on the old one Design Review: 3.3V Logic to 12V Logic (Uni-directional and Bi-directional) I'm looking for feedback and improvements on my design below. Specific questions are at the end. I created this as an attempt to answer my own, . From my feedback there, it seems like I needed to be more clear in my requirements. These are screenshots from Eagle. If there's a better way to share, please let me know so I can correct it. Entire board  The overall purpose of this board is to translate between 12V logic, and 3.3V logic. The top portion of the board represents the 12V side. The LEDs are placeholders to indicate whether the 12V signal is HIGH or LOW. In practice, these would be replaced with more , requiring up to 3A. The switches are also placeholders, allowing one to manually turn the 12V signal on and off. They are only for test purposes, the &quot;real&quot; 12V signal would be coming as the output from other relays. The bottom half is the 3.3V side. This will be connected to a  (BBB). The board will connect to 2 output GPIO pins and 2 input GPIO pins of the BBB. Overall, I want to translate the 3.3V I/O from the BBB to the 12V signals on the other side (to control more relays and read their signals). I have designed 3 modules to control both directions individually, and together. 3V3_TO_12V Module  This module converts the 3.3V GPIO output from the BBB to a 12V signal on the other side. When the 3.3V signal is low, the 12V signal is low. When the 3.3V signal is high, the 12V signal is high. To do this, the 3.3V GPIO output is connect to a , which turns a  relay on and off. This switches the 12V power as output of the module to be used elsewhere. 12V_TO_3V3 Module  This module converts a 12V signal to 3.3V signal, to be read by a GPIO input from the BBB on the other side. When the 12V signal is low, the 3.3V signal is low. When the 12V signal is high, the 3.3V signal is high. To do this, the 12V signal simply turns a  relay on and off. This switches the 3.3V power to be read as input by the BBB. DUAL_12V↔3V3 Module  This module combines the previous two modules to create a bidirectional translation. If the 12V side is high, the 3.3V input to the BBB GPIO should be high. If the 3.3V output from the BBB GPIO is high, then the 12V side should be high too. It's similar to a logical OR, if either side is high, the corresponding signal on the other side should be high too. A single 12V signal has to be split into individual input and output signals on the 3.3V side for the BBB. Questions  Is the  and  relay combination overkill for having the BBB GPIO output control the 12V power line? I like the isolation and safety it provides, but it seems too much (in terms of cost and board space) Is there a better solution for the 12V to 3.3V conversion. I like the simplicity of the  relay switching a 3.3V signal, but it takes up lots of room. Does the DUAL_12V↔3V3 Module (which combines each translation direction) even make sense? This seems wasteful to use 2 relays and a high side driver, but I haven't found simpler solution that achieves the same result. Should I add pulldown resistors for the BBB GPIO inputs, or are the internal pulldown resistors good enough?  Any other feedback is welcome. I'm new to electronic design. Cartoon with a young unicorn and a demon In the late 80s or early 90s I remember watching an animated series that followed a young unicorn and a demon.   In one episode the unicorn gave the demon his horn, and the unicorn almost died.   In another episode there was a man who was able to turn people into human shaped building blocks and built a huge tower from them.   Those are the two scenes I remember with any clarity.   Does anyone have any idea? I need to display attachments on a visual force page for the Case object.  This is the code I am using. I had it working for awhile, but it somehow broke down. It gets all the attachments, but it will not show the images.   &lt;apex:repeat value="{!Case.attachments}" var="att"&gt;             &lt;apex:panelgrid columns="1"&gt;                 &lt;h1&gt;Image/h1&gt;                 &lt;apex:image url="/servlet/servlet.FileDownload?file={!att.Id}"/&gt;             &lt;/apex:panelgrid&gt; &lt;/apex:repeat&gt; Last time I asked a similar question but that was about svn related versioning info. Now I am wondering how to query windows "File version" attribute about eg. a dll. I payed attention to wmi and win32file modules as well without success. $_POST empty on utf-8 characters What methods of ‘clearfix’ can I use? How to read one filesystem from a whole disk image file? I ran these commands:  VBoxManage clonehd d6b9f0a5-98df-48ca-83c8-91a0809ec349 --format RAW Debian.raw sudo dd if=~/.VirtualBox/HardDisks/Debian.raw of=/dev/sda5   When I try to mount the partition, I get this complaint:  EXT4-fs (sda5): VFS: Can't find ext4 filesystem   Now I know that the VM had an ext4 partition. What did I do wrong? I'm working from the URL I found here:    My ssh client is Ubuntu 64 bit 11.10 desktop and my server is Centos 6.2 64 bit. I have followed the directions. I still get a password prompt on ssh.  I'm not sure what to do next. idempotents acting as local identities Let $R$ be a ring with unity (not necessarily commutative) and $I$ an ideal of $R$.  Suppose that for every element $a \in I$ there exists an element $c\in I$ such that $ac=a$. Note that $c$ is related to $a$. Now we have the following question:  Can we say that  for every element  $a\in I$ there exists an idempotent element $c\in I$ such that $ac=a$?    Of course we have many examples such that the answer is true for them but in general  we don't know. Is there any noun in English which changes the first letter in the plural? Plenty of nouns change the second letter to become plural (man->men, goose->geese) but does anything change its first letter.  I've hunted high and low over the internet, and spent ages browsing the questions at  but I can't find anything. I've had a couple of answers today where the OP indicated via a comment that I solved their problem, but the question wasn't upvoted or accepted.  In both cases the person probably wasn't able to upvote since they were new, but they could have accepted my answer. I felt a little guilty asking them to accept the answer, but since it solved their problem I felt that it would help others who stumbled on the question trying to solve their own problem to know that my solution really was the answer. Is asking the OP to accept your answer when they've said that it solved their problem a reasonable thing to do or does that feel like nagging for reputation? Determine whether a number is prime How do I determine if a number is prime?  I'm writing a program where a user inputs any integer and from that the program determines whether the number is prime, but how do I go about that? One way function existence Let $x = (x_1, x_2,...,x_n)\in\{0,1\}^n$ for $n\in\mathbb{N}$. Prove that if one-way functions (OWFs) exist, then there exists a one-way function $f$ such that for every bit $i\in[1,n]$ there exists an algorithm $A_i$ such that: $$\Pr[A_i(f(x)) = x_i] \geq \frac{1}{2} + \frac{1}{2n}$$ I'm having trouble understanding this. Live USB for installation does not boot, black error screen followed by visual artifacts on a purple screen I'm trying to install Ubuntu 18.04 desktop with Rufus on a computer with the following specs:  CPU: AMD Ryzen 5 2600 MOBO: ASUS Prime B450M-A/CSM RAM: G-Skill Ripjaws DDR4 F4-2400C15D-16GVB GPU: Nvidia GeForce GTX750 PSU: Apexgaming AG-650M SSHD: Seagate Firecuda Compute mATX: Rosewill SCM-01  Basically it boots from the USB (FAT32) and brings up a black error screen with words and numbers. Then it transitions to the purple splash screen with &quot;ubuntu&quot; and 5 dots, however the screen shows various visual glitches depending on which USB port I plug into. When trying to boot the computer, it boots to a black screen with the following error message: ACPI Error: Needed [Integer/String/Buffer], found [Region]    that shows what I mean. Why are z-values replaced with zero after in_memory use in Python? How to install World of Warcraft? Is there a direct download link with a raw data dump of Stack Overflow? (not a torrent) I would like to create a local MySQL copy of Stack Overflow for academic purposes (school project). As far as I know, the database dump of the  database is available only in an XML format that I will have to convert to SQL on my own with some tool.  Most of direct download links I found were broken (404). The only non-torrent source that I have found and that is still alive is  but the latest Stack&nbsp;Overflow dump there is from October 2009, content of which looks like this:    Where could I find a direct download link with the Stack&nbsp;Overflow dump?    Note: I am not able to use torrents due to network policies, yet for the completeness of this question, here's the link that might help someone:    Other related questions / links that haven't helped me:     ~ all links there give 404  ~ from September '09 with another broken link  ~ from about a year ago with a clearbits.net link  ~ also not working anymore