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Articles indexed Monday November 5 2012

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• What is the difference between "data hiding" and "encapsulation"?

  - by Software Engeneering Learner

  I'm reading "Java concurrency in practice" and there is said: "Fortunately, the same object-oriented techniques that help you write well-organized, maintainable classes - such as encapsulation and data hiding -can also help you create thread-safe classes." The problem #1 - I never heard about data hiding and don't know what it is. The problem #2 - I always thought that encapsulation is using private vs public, and is actually the data hiding. Can you please explain what data hiding is and how it differs from encapsulation?

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• Problem with graphic Ubuntu 12.04 (not sure if it's because of the graphic driver)

  - by Duy Nguyen

  Ubuntu 12.04 was functioning properly . Then after an update, some graphic elements stop working properly. I could not launch programs that has 3D elements. Work space switcher's window displays 2D window instead of a 3D like usual. In Details menu, the Graphic row is blank. I am using Intel GMA 4500MHD graphic card. I am guessing that the driver is not properly installed? Anyone has the same issue? Please help!

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• Full disk encryption with seperate boot and encrypted keyfile storage: Two-Form Authentication

  - by Cain

  I am trying to setup true Full Disk encryption with two-form authentication on 12.04 and can not find out how to call a keyfile for the encrypted root out of another encrypted partition. All documentation or questions I am finding for whole or full disk encryption only encrypts separate partitions on the same disk. This is not what most are calling full disk encryption, /boot is not on a partition on the root drive, rather it is on a usb stick as sdx1. Instead root is on a logical partition on top of a LUKS container. Luks is run on the whole disk, encrypting the partition table as well. All drives in the machine are completely encrypted and to open it it requires a USB drive (what I have) as well as a passphrase (what I know) resulting in Two-Form Authentication to boot the machine. Device sdx cryptroot vg00 lvroot / There is no passphrase to open the encrypted root device, only a keyfile. That keyfile is kept on the usb drive with /boot, in its own encrypted partition (I'll call this cryptkey). In order for the root file system (cryptroot) to be opened, initramfs must ask for the passphrase to cryptkey on the usb drive, then use the keyfile inside that to open cryproot. I did manage to find what I think is the how-to I used to do this once before: http://wiki.ubuntu.org.cn/UbuntuHelp:FeistyLUKSTwoFormFactor I already have the system installed and can chroot into it, however, I can not get it to call for the keys on the USB during boot. I did find a how-to saying I needed to make a cryptroot conf for initramfs but, I believe that is for a passphrase: https://help.ubuntu.com/community/EncryptedFilesystemLVMHowto#Notes_for_making_it_work_in_Ubuntu_12.04_.22Precise_Pangolin.22_amd64 I also tried to setup crypttab. However, crypttab only works for drives mounted after the root drive as calling for a keyfile on a device not yet mounted to the system doesnt work. The Feisty how-to included scripts that would be run during boot instructing initramfs to mount the usb drive temporarily and call the keyfile for root which worked quite well except those scripts are outdated now, many of the things they relied on have been merged into something else, changed, or simply don't exist anymore. If I have missed a clear how-to for this, that would be wonderful, I just don't think I have.

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• Best solution for a team home server

  - by aliasbody

  I created a home server with Ubuntu 12.04 Server (using an old Netbook with an Atom CPU and 512Mb). The idea is just to be used for a small team (maximum 10 persons) that will have constant access by SSH to the main projects and could add features with Git, and will, as well, have their own directory (with VirtualHost configured) for their own personal projects. Everything is configured and running, but my question is : What is the best solution here for everyone to work? It is to have them on the http group and then all have access as normal users to the /var/www folder (that also contains GitWeb and Drupal), or would be to create a new user named after the project (as an example) where only those with the password could have access to work (configured with VirtualHost). Notice: The idea is to have 1 person responsible of the server directly (since he is the one who is hosting it), 2 more people that will have access to the root from their home in order to configure anything from their home, plus anyone else that joins the group without any root access, but just the necessary access to create personal works and work with Git.

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• MPD to play music to single channel of my multi-channel card?

  - by hany tawfik

  I installed an Ubuntu 12-04 LTS server for a special background music application of mine, where I am using the server with an Asus Xonar DS sound card. The installation is successful, the MPD is working, the sound card is working with Alsa and its libraries installed accept for Alsa-oss. Alsamixer is working fine with left/right sides of each channel volume control through Q/Z letters shortcut when alsamixer is open in terminal . using the command " speaker-test -Dplug:surround71 -c8 -l1 -twav " I can hear every voice message coming out from the card at the right connector, so "front right/ front left" voice message are coming from first output in the card back, while the other outputs are silent..so on. The problem is that MPD is playing on all outputs simultaneously the same audio. I have been trying various configurations for the last 12 days with out any success, including trying to put mappings in the /etc/asound.conf Can any body help me achieve the above, or direct me to the right configuration of MPD or asound.conf

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• Upgraded Ubuntu 12.04 -> 12.10 and Drupal 7 site now get error

  - by Paul B

  I do all my Drupal 7 webdev and today I took advantage to upgrade my local WebDev box O/S to Ubuntu 12.10 from 12.04 and now I get the following errors for all my D7 projects on my localhost WebDev box (Ubuntu 12.10) It was all fine pre Ubuntu 12.04: Error The website encountered an unexpected error. Please try again later. Error message PDOException: SQLSTATE[42000]: Syntax error or access violation: 1286 Unknown storage engine 'InnoDB': SELECT expire, value FROM {semaphore} WHERE name = :name; Array ( [:name] => variable_init ) in lock_may_be_available() (line 167 of /var/www/jobsdaily/includes/lock.inc). A quick research and look into the phpmyadmin (3.4.11.1) and it seems InnoDB is an issue and when I click on a table to see data I get #1286 - Unknown storage engine 'InnoDB'. I have all my D7 sql backed up, but don't really want to go down the whole 'import' route, since it's 10 months work! Anyone had this issues and can anyone suggest fix ideas? Thanks

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• Unrecoverable error during WUBI installation

  - by john

  I tried to install 12.10 on my PC with Windows 7 installed, but I don't have a CD drive and my PC doesn't support USB booting, so I tried the Windows Installer (WUBI). I had the ISO image mounted with daemon tools, so the Windows installer took those files and used them (I guess, because it didn't download any files). Everything went right, but when it prompted me to reboot, I rebooted the PC and then it starts to install, but when the installation process starts, a message that says: The installation found a unrecoverable error. pops out and makes me reboot, then when I select Ubuntu in the operating system selection screen, it says that an error occurred.

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• MySql #2002 problem

  - by Systeem Faillure

  when i try to login in apache i get #2002 error. when i try to login via terminal it ask my password mysql -u root and i get ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) i tried to remove mysql and install it again and nothing happen ( i cant even remove it) i try to reboot apache but still nothing. i tried to reboot my pc and of course still aint working. in terminal i put sudo start mysql i got this: start: Job failed to start mysql -ubob -hlocalhost -P3306 -p got me this ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) sudo service mysql stop gave me this stop: Unknown instance: my.cnf * Basic Settings # user = mysql pid-file = /var/run/mysqld/mysqld.pid socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /var/lib/mysql tmpdir = /tmp lc-messages-dir = /usr/share/mysql skip-external-locking # i tried to find if there is a file in my /var/run/mysqld/ or in /var/tmp/ and dint find the file mysqld.sock .. i looked in /var/log/mysql/ and dont even have anything in it can help me???i try to find help on google for hours and dint help at all... -------EDIT---------- salem : sudo service mysql start i get start: Job failed to start cat /var/log/syslog | grep mysql here http://paste.ubuntu.com/1335984/ /var/run/mysqld/ this folder exist but it dosent have anything in it /var/run/mysqld/ i get total 0 drwxr-xr-x 2 mysql root 40 Nov 5 22:31 . drwxr-xr-x 25 root root 860 Nov 5 22:32 .. sorry that i post anything my terminal gives but i am noob at this. hope this information will do.

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• Create a custom shortcut that types clipboard contents

  - by briankb

  I want to paste my clipboard contents to a remote session such as VNC, IPMI, or Raritan. To accomplish this, I installed xdotool and clip. Then I wrote a simple command that types the clipboard contents: xdotool type "$(xclip -o)" This works if I stay in a terminal window, and type that command myself. It types back my clipboard contents when I run the command. Of course now I want to make this into a hotkey that works in any window. However, if I create a custom shortcut using Keyboard settings, it doesn't work. If I assign a hotkey Alt+K to the shortcut, nothing happens when I press it. If I use Ctrl+K, unexpected behavior occurs to whatever window has focus. e.g. my terminal window size shrinks (it's somewhat amusing, actually). Similar results occur if I save it as a script and call the script, or if I encapsulate the command with sh -c. How can I make practical use of the powerful xdotool type command?

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• Zotero error in libreoffice

  - by arno

  I installed Zotero standalone in 12.10 64bit. Some problems which I managed to fix. The one that remains is an error saying "openoffice.org could not communicate with Zotero. make sure zotero standalone or Firefox are open and set to an online state and try again". That's when I click any button in the Zotero toolbar in libreoffice. Firefox doesn't open with a the plugin installed and a working internet connection. The Zotero troubleshooting which mentions this error was of no help to me. I find reports about this bug going back as far as 2009 but I haven't found anything of help.

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• How to share Rhythmbox playlists in a network?

  - by Ralf Hersel

  My music is stored on a Synology NAS and Rhythmbox has access via NFS to the music files; works perfect. But how can I share the Rhythmbox playlists? I tried to store the playlists.xml file on the NAS and created a link in the home/user/.local/share/rhythmbox directory to the playlists.xml on the NAS but Rhythmbox converts the link to a local file. Any idea on how to force Rhythmbox to use the link to the playlists.xml file on the NAS?

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• Encrypt folders out of Home

  - by igi

  Is there a way to encrypt a folder, which is not in /home but even in a different partition, so only my user can access/read contained files? Alternatively, I would like to understand if it is possible to turn a complete ext4 partition into an encrypted volume, which would be mounted at user login. If possible, I would like to make the change without reinstalling Ubuntu. My PC has (mount output): /dev/sda1 on / type ext4 (rw,errors=remount-ro) /dev/sda3 on /home type ext4 (rw) /dev/sda4 on /home/igor/Personale type ext4 (rw) sda4 is the partition containing folders I would like to protect. Thanks!

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• After Installation Whole Disk Encryption? 12.04

  - by Luke

  I know some fragments of this question have been asked in previous posts and I have reviewed them - however I have a more thorough question... I did not choose to do whole disk encryption when I used the alternative installer to install my 12.04 distro. I thought that truecypt worked with linux on system drive (whole disk) encryption - but sadly found out it did not. I have totally tweaked and pimped out my installation and I do not want to have to go back and "install" to just get whole disk encryption. Any alternatives that anyone knows of? I don't want just /home... I want the whole system installation protected and made secure so that when I boot I get a password to unencrypt.

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• swapon --all --verbose : 'read swap header failed: Invalid argument'

  - by user66088

  Recently ran through EnableHibernateWithEncryptedSwap and ran the following command: swapon --all --verbose and received: 'read swap header failed: Invalid argument' How do I fix this? Here's some more pertinent output... Output of sudo fdisk -l: Disk /dev/sda: 80.0 GB, 80026361856 bytes 255 heads, 63 sectors/track, 9729 cylinders, total 156301488 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00006d20 Device Boot Start End Blocks Id System /dev/sda1 * 2048 499711 248832 83 Linux /dev/sda2 501758 156301311 77899777 5 Extended /dev/sda5 501760 156301311 77899776 8e Linux LVM Disk /dev/mapper/ubuntu--t10194-root: 75.5 GB, 75539415040 bytes 255 heads, 63 sectors/track, 9183 cylinders, total 147537920 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/mapper/ubuntu--t10194-root doesn't contain a valid partition table Disk /dev/mapper/ubuntu--t10194-swap_1: 4227 MB, 4227858432 bytes 255 heads, 63 sectors/track, 514 cylinders, total 8257536 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x08040000 Disk /dev/mapper/ubuntu--t10194-swap_1 doesn't contain a valid partition table Disk /dev/mapper/cryptswap1: 4225 MB, 4225761280 bytes 255 heads, 63 sectors/track, 513 cylinders, total 8253440 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xd2236983 Disk /dev/mapper/cryptswap1 doesn't contain a valid partition table Thanks for any and ALL help!

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• Network printer problem with 12.04

  - by G. He

  I had an HP LaserJet 3030 printer connected to an Ubuntu box. It worked fine with 11.10. I was able to print from Ubuntu as well as from Windows and Mac from the home network. About a month or so ago, I upgraded 11.10 to 12.04, then things started to falling apart. My Windows 7 laptop couldn't print to the printer any more. Today, I installed many updates on 12.04, hoping that would fix the printing problem. Unfortunately, it made the situation much worse. Now not only my Windows 7 laptop won't print, my XP desktop won't print either. Every time I print something from the Windows computer, the Ubuntu box logs an error message in /var/log/samba/log.'machineName' as: _spoolss_OpenPrinterEx: Cannot open a printer handle for printer \\server. It is interesting that it uses the server name as the printer, not the \\server\xyzprinter as the printer name. Anyone had a similar problem? Anyway to work around the problem?

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• Ubuntu 12.04 won't boot from USB

  - by user986871

  I downloaded Ubuntu 12.04, then using the tool Startup Disk Creator i made the live usb. I checked that it's bootable Device Boot Start End Blocks Id System /dev/sdb1 * 62 15635593 7817766 c W95 FAT32 (LBA) Now on my lap top it boots nicely, but on two other machines that don't have any installation of ubuntu(no Grub) it doesn't boot. I changed the booting order so that USB is before HDD. So i think i did everything i know, but no luck. How can i use this USB drive on other devices that don't have any previous ubuntu installation.

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• Apache2's recursive directory permission requirement

  - by Sn3akyP3t3

  The experience I've had thus far is from Ubuntu 10.04 and 12.04 64 bit OS so if there are other OS differences I'd like to know if this is an OS specific problem or not. The issue I've experienced is mostly confusion. Once the cause of the problem is identified and corrected there are no further related problems experienced. The symptom is Error 403 forbidden. Typically the cause is attempting to use a directory other than /var/www/ for content. The cause is simply permissions, but its puzzling why the required permissions must persist from at least one level deeper than root onward till the current working directory where the content is stored. For example: Alias /example/ "/home/user/permissions/can/be/confusing/with/apache/" <Directory /home/user/permissions/can/be/confusing/with/apache/> Options FollowSymLinks MultiViews AllowOverride None Order allow,deny Allow from all </Directory> With www-data being the user that spawned apache and "user" being a member of the www-data group. Thus, if ownership of /home/user/* is user:user then all that is necessary to display content with apache is permssions of read and execute. So d---r-x--- should suffice, but for practical purposes I'm using drwxr-x--- for most. However, if all directories /home/user/* are permissions of drwxr-x-- and /home/user/ itself has permissions of drwx------ then content will always fail with error 403. This is strange because it doesn't follow what I would consider traditional logic of permissions which should only be applicable to the current working directory or a particular file in that directory and not any directory further back in the chain. Is this by design or is it a bug?

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• HTML 5, Fluid Pages and Google Mobile Index

  - by Bob

  I am currently migrating my site to HTML5, at the same time designing pages so that they are "fluid" and are equally presentable for a mobile or a large screen. I took the fluid approach so as not to have to develop a separate application for mobile devices and I'm pleasantly surprised with the results that look equally as good on an iPhone as they do on a large screen. Then I went into the Google Webmaster Tools facility and became aware of the Google Mobile Index. I'm confused now as HTML5 doesn't seem to be supported by Google Mobile Indexing. Does this mean that when I go live with my new "pride and joy" HTML5 site on a mobile it won't appear on any Google searches as it's not in the Google Mobile Index?

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• Blender multiple animations and Collada export

  - by Morgan Bengtsson

  Say I have a simple mesh in Blender, with two keyframes, like so: Then, another animation for the same mesh, also with two keyframes: Theese animations worke fine in Blender and I can switch between them in the Dopesheet, where they are called "actions": The problem arises, when i try to export this to the Collada format, for use in my game engine. The only animation/action that seems to be carried over, is the one currently associated to the mesh. Is it possible to export multiple animations/actions for the same mesh, to the Collada format?

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• Best way to generate pieces in match-3 games, and then tracking them?

  - by JonLim

  I've been working on a match-3 style game in Actionscript using Flixel, and so far, I've been able to build the core mechanics of the game, including board generation, piece generation, piece swapping and movement, and checking algorithms. However, I am now running into issues with clearing out pieces and letting the above pieces fall down and generating new pieces. The reason I'm running into these issues is that when all of the pieces are generated, the pertinent values (position, sprite ID, and sprite object) are pushed into an array that helps me track everything, all the time. When pieces are moved, I swap the values of the corresponding arrays and life goes on. And that array is the core of my problem: if a row in the middle of the board clears out, ideally, all of the pieces above the cleared pieces should fall down to take their place and new pieces are generated at the top and also fall into place. Except if I try to do that now, all the pieces can fall down, but then I'd have to bump all of their values into the right arrays (oh god my head) and then generate new pieces and fit THOSE into the correct place in the array. Am I overthinking this? Or is there a far better way to track these pieces? Thanks guys!

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• How to manage my model

  - by Christophe Debove

  I have in my model, a list of Classes : Player, NonPlayerCharacter, Monster, Item, NonMovableItem etc With AndEngine I've a list of sprite for each piece of my model, How can I manage the relashionship between my model's classes and the graphical elements, what is the degree of abstaction recommended for my problem? One sprite for one Model or one Model for one Sprite or n for n for exemple If I do drag&drop have I to make abstraction of the Sprite Class, another exemple a map is a List of sprite or a list of element of my model?

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• XNA GUI: Creating a 'scroll pane' widget

  - by Keith Myers

  I'm trying to create a simple GUI system and am currently stuck on how to implement a textarea with a scrollbar. In other words, the text is too large to fit into the view area. I want to learn how to do this, so I'd rather not use an already rolled API. I believe this could be done if the text were part of a texture, but if the game had a lot of unique dialog, this seems expensive. I researched creating a texture on the fly and writing to it, but came up with nothing. Any suggested strategies would be appreciated. I believe it boils down to: text in a texture and how? Or something I have not thought of...

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• Rendering a big game universe - bitmaps or vector graphics?

  - by user1641923

  I am new to an Android development, though I have much experience with Java, C++, PHP programming and a bit experience with vector graphics too (basic 3d Studio Max, Flash, etc). I am starting to work on an Android game. It is going to be a 2D space shooter/RPG, and I am not going to use any game engines and any 3D party libs. I really want to create a very large game universe, or even pseudo-infinite (without visible borders, as if it were a 2D projection of a sphere). It should include 10-12 clusters of 7-8 planets/other space objects and random amount of single asteroids/comets, which player can interact with and also not interactive background. I am looking for a least complicated aproach to create such a universe. My current ideas are: Simply create bitmaps with space scenery background so that they can be tiled seamlessly repeated and construct my 2D universe of this tiles, then place interactive objects (planets, other spaceships) on it. Using vector graphics. I would have a solid color background, some random background objects and gradients here and there. My problems here: Lack of knowledge of how well vector graphics is integrated in Android. Performance? Memory usage? Does Android manage big bitmaps well? Do all of the bitmaps have to be in memory during all game process? I am interested in technical details regarding each of the ideas and a suggestion, which I should go with.

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