I installed some additional desktop environments in ubuntu 18.04, and I don't know if this has something to do with it, but around the time installing these desktop environments, I discovered that my boot screen was not the standard ubuntu one, rather the ubuntu budgie boot theme. I tried to fix it, but I messed up some plymouth related stuff, so I ended up reinstalling the default plymouth theme for ubuntu 18.04.  Now I discovered that my grub menu background is black, not the standard "ubuntu-purple", and I don't know if it has something to do with the plymouth related stuff, but anyways, the question is: "how can I fix the grub menu back to the defaults?".   My GRUB menu version is 2.02 (output of grub-install --version is grub-install (GRUB) 2.02-2ubuntu8.13), and I don't know if this is the standard version of GRUB in ubuntu 18.04, so that is another question I'm wondering about.  Thanks for all answers!
How to do this manually, not installing any tools?
So I am using cryptopp to encrypt a file in a project and I am using AES-GCM. I have a 256bit key and a 128bit ivec and a 128bit tag that I use to encrypt files.  However, I want to know where the authentication tag is stored? I notice if I specify a tag size of 0 then the encrypted file size is the same number of bytes as the original file.  Is the authentication tag simply appended to the end of the file? In Java, how do I call a base class's method from the overriding method in a derived class? I have two Java classes: B, which extends another class A, as follows :  class A {     public void myMethod() { /* ... */ } }  class B extends A {     public void myMethod() { /* Another code */ } }   I would like to call the A.myMethod() from B.myMethod(). I am coming from the , and I don't know how to do this basic thing in Java. I've often come across posts on forums or other websites where you see people joking in such a manner about running/logging in as root as if it's something awful and everyone ought to know about it. However, there isn't much that a search reveals on the matter.   It may be widely known to Linux experts, but I really don't know why. I remember always running as root when I first tried Linux years ago (Redhat and Mandrake) and don't remember running into any problems because of that.   There are actually some distros that have a bright red background with alert signs all over it as wallpaper for the root user (SuSe?). I still use the "Administrator" account for regular use on my Windows installation and haven't ever run into any problems there either. How to create a virtual audio device and stream audio input with it Here's my concrete problem:  I am broadcasting a game via XFire and it uses the Windows audio device to capture any audio I receive. As I am broadcasting, other users who watch the video stream are communicating with me over Skype, and they hear themselves back within the video stream and it is entirely logical since I am broadcasting the audio I hear.  What I want to do is create another audio device within Windows and redirect (pipe) ONLY the audio input from that game and not the input reveived from Skype. I would then tell XFire to use that newly created "virtual" audio device to broadcast and therefore my partners won't hear themselves back.  Is it possible to create another audio device and redirect only wanted input streams to it? At the onset of my live usage in Ubuntu Gnome 15.10, use a bash script to set the colour of my gnome-terminal. The code used is link=/org/gnome/terminal/legacy/profiles:/:b1dcc9dd-5262-4d8d-a863-c897e6d979b9 dconf write $link/background-transparency-percent '10' dconf write $link/scrollback-unlimited true dconf write $link/use-theme-colors false dconf write $link/use-theme-transparency false dconf write $link/use-transparent-background true dconf write $link/foreground-color 'rgb(0,43,54)' dconf write $link/background-color 'rgb(131,148,150)'  The last 2 lines of the code give a key-value error. When I look at the dconf-editor org&gt;gnome&gt;terminal&gt;legacy&gt;profiles:&gt;{Default profile} the attributes  foreground-color background-color  are unavailable. How do I get rid of the error? Note: When done manually via gnome-ternimal&gt;Edit&gt;Profile Preferences&gt;Colours&gt;Built-in schemes the above attributes appear in the same location in dconf-editor. In a couple weeks, I will have a long layover in Cairo on a trip from Mumbai to Toronto. I get to Cairo on Sunday at noon and leave for Toronto on Monday at about 1 AM.  I am travelling on EgyptAir business class. While browsing for people who have experiences with a similar itinerary, some people seemed to have said they they were put up ina  hotel by the airline. However, I did not see anything about this when I booked my ticket.   allows me to enter my status (i.e. citizenship etc.) which results in a .  It doesn't appear like I need a transit visa- however it specifies that:     Leaving the airport is permitted for passengers with transit time   between 6 and 12 hours   My transit time 13.5 hours.  Now for my questions:   Is it an issue that my transit time is longer than 12 hours? Can I still leave the airport? What are my options with regards to airport hotels, etc.? Any other recommendations about how I could best utilize my time while in Cairo? How does the "tail" command's "-f" parameter work? $ tail -f testfile   the command is supposed to show the latest entries in the specified file, in real-time right? But that's not happening. Please correct me, if what I intend it to do is wrong...  I created a new file "aaa" and added a line of text and closed it. then issued this command (first line):  $ tail -f aaa xxx xxa axx   the last three lines are the contents of the file aaa. Now that the command is still running (since I used -f), I opened the file aaa via the GUI and started adding a few more lines manually. But the terminal doesn't show the new lines added in the file.  What's wrong here? The tail -f command only shows new entries if they are written by system only? (like log files etc) SUB-TREE WITHIN A TREE in MySQL  In my MYSQL Database COMPANY, I have a Table: Employee with recursive association, an employee can be boss of other employee. A self relationship of kind (SuperVisor (1)- SuperVisee (∞) ).     Query to Create Table:    CREATE TABLE IF NOT EXISTS `Employee` (   `SSN` varchar(64) NOT NULL,   `Name` varchar(64) DEFAULT NULL,   `Designation` varchar(128) NOT NULL,   `MSSN` varchar(64) NOT NULL,    PRIMARY KEY (`SSN`),   CONSTRAINT `FK_Manager_Employee`                 FOREIGN KEY (`MSSN`) REFERENCES Employee(SSN) ) ENGINE=InnoDB DEFAULT CHARSET=latin1;   I have inserted a set of tuples (Query):    INSERT INTO Employee VALUES   ("1", "A", "OWNER",  "1"),     ("2", "B", "BOSS",   "1"), # Employees under OWNER   ("3", "F", "BOSS",   "1"),   ("4", "C", "BOSS",   "2"), # Employees under B  ("5", "H", "BOSS",   "2"),   ("6", "L", "WORKER", "2"),   ("7", "I", "BOSS",   "2"),   # Remaining Leaf nodes     ("8", "K", "WORKER", "3"), # Employee under F        ("9", "J", "WORKER", "7"), # Employee under I        ("10","G", "WORKER", "5"), # Employee under H   ("11","D", "WORKER", "4"), # Employee under C  ("12","E", "WORKER", "4")     The inserted rows has following Tree-Hierarchical-Relationship:                A     &lt;---ROOT-OWNER         /|\                     / A \               B     F      //| \    \              // |  \    K        / | |   \                       I  L H    C         /     |   / \  J     G  D   E   I written a query to find relationship:    SELECT  SUPERVISOR.name AS SuperVisor,          GROUP_CONCAT(SUPERVISEE.name  ORDER BY SUPERVISEE.name ) AS SuperVisee,          COUNT(*)   FROM Employee AS SUPERVISOR    INNER JOIN Employee SUPERVISEE ON  SUPERVISOR.SSN = SUPERVISEE.MSSN  GROUP BY SuperVisor;   And output is:    +------------+------------+----------+ | SuperVisor | SuperVisee | COUNT(*) | +------------+------------+----------+ | A          | A,B,F      |        3 | | B          | C,H,I,L    |        4 | | C          | D,E        |        2 | | F          | K          |        1 | | H          | G          |        1 | | I          | J          |        1 | +------------+------------+----------+ 6 rows in set (0.00 sec)   [QUESTION] Instead of complete Hierarchical Tree, I need a SUB-TREE from a point (selective) e.g.: If input argument is B then output should be as below...  +------------+------------+----------+ | SuperVisor | SuperVisee | COUNT(*) | +------------+------------+----------+ | B          | C,H,I,L    |        4 | | C          | D,E        |        2 | | H          | G          |        1 | | I          | J          |        1 | +------------+------------+----------+      Please help me on this. If not query, a stored-procedure can be helpful. I tried, but all efforts were useless! How to get class object's name as a string in Javascript? C++ cout hex values? Bravo for allowing comment editing, but what's the explanation for enforcing a five-minute window?  I think this might be over-engineering. If I have a spelling mistake or an inaccuracy I'd like to fix, I don't think the fact that five minutes has elapsed should prevent me from fixing it.  Further, if you are worried people will edit their comments in a way that makes the comment thread nonsensical, they can already do this by deleting their comment. So, limiting the ability to edit isn't really helping much in that regard.  Update  If people don't like this idea, I'm definitely open to hearing your reasons. For now, it seems like an unnecessary limitation of a quite awesome feature.  Update 2  Regarding John's scenario...     Me: Obama is cool!   You: You are right, man!      My edit: Obama is an idiot!   You: You are right, man!   ...this problem can still occur with deletions...     user1: Obama is cool!   user2: No, McCain is cool!   you: You are right, man!        user1: Obama is cool!   ---- deleted -----   you: You are right, man!     So, yes, editing could be abused as you suggest, but discontinuities can occur already because of deletions (and as someone else mentioned, because upvoted comments get prioritized upward).  As for Jeff's argument about rate limiting, I agree that is important, but I don't understand why you can't just use a CAPTCHA to prevent too many edits in a short period of time. Why am I asked for a credit card number to download a free app? I  want to download free app in my iPod touch device and i have the following doubts.  Kindly resolve me doubts.   when i try to download it asks my credit card security number. since i am trying to download free app , why do i need to provide my credit card security code? Will i be debited for downloading the free app from app store?   I cant able to find any information regarding this on apple.  Please provide me some references about this from apple and please resolve my doubts.  Thanks a lot. I am often interested in the installation triggers (postinst, postrm) or certain parts of packages (like /usr/share and /etc). Currently, I am running the next command to retrieve the source code:  apt-get source [package-name]   The downside is, this file is often much bigger than the binary package and does not reflect the installation tree.  Right now, I am downloading the packages through :      Download the actual file   This takes too long for me and as someone who really likes the shell, I would like to do something like the next (imaginary) command:  apt-get get-deb-file [package-name]   I could not find something like this in the . The most close I found was the --download-only switch, but this puts the package in /var/cache/apt/archives (which requires root permissions) and not in the current directory. $VAR vs ${VAR} and to quote or not to quote It is much more convenient and cleaner to use a single statement like  import java.awt.*;   than to import a bunch of individual classes  import java.awt.Panel; import java.awt.Graphics; import java.awt.Canvas; ...   What is wrong with using a wildcard in the import statement? When to use reinterpret_cast? I am little confused with the applicability of reinterpret_cast vs static_cast. From what I have read the general rules are to use static cast when the types can be interpreted at compile time hence the word static. This is the cast the C++ compiler uses internally for implicit casts also.  reinterpret_casts are applicable in two scenarios:   convert integer types to pointer types and vice versa  convert one pointer type to another. The general idea I get is this is unportable and should be avoided.     Where I am a little confused is one usage which I need, I am calling C++ from C and the C code needs to hold on to the C++ object so basically it holds a void*. What cast should be used to convert between the void * and the Class type?  I have seen usage of both static_cast and reinterpret_cast? Though from what I have been reading it appears static is better as the cast can happen at compile time? Though it says to use reinterpret_cast to convert from one pointer type to another? In the past, both Philosophy and Science were one. However, because of the vastness of Science, it was cut off. I am inclined to go along the same line of thinking, but, is there a way to merge both disciplines once again? Heartbleed: are services other than HTTPS affected? The OpenSSL 'heartbleed' vulnerability () affects webservers serving HTTPS. Other services also use OpenSSL. Are these services also vulnerable to heartbleed-like data leakage?  I'm thinking in particular of   sshd secure SMTP, IMAP etc -- dovecot, exim &amp; postfix VPN servers -- openvpn and friends   all of which, on my systems at least, are linked to the OpenSSL libraries. Render issue - Model doesn't appear to be on any layers and won't render Really odd on this... using Blender 2.75... I started modelling and lost the objects from the 3d view, but they were still showing in the object lists on the outlier... I was able to copy them and continued working... when I did a test render I discovered that only the original lost objects were rendering and nothing that I had modelled over the previous 2/3hrs was showing up...  I have no idea what I did but I created another 3d view and the original bits showed up along with the layer buttons which had been missing from the screen which I thought was just a new feature from  2.75...!  Picture to show the 2 screens, top one doesn't render but bottom one does    Any idea's what I've done? kidle_inject causing very high load Whenever kidle_inject starts running on my system the load shoots up. In general it only gets to a load of around this 5.23, 3.65, 2.54 but a lot of the time it jumps up past the 15 mark on each of them. At that point the system grinds to a halt and I have to power it off.  This only happens when the kidle_inject process starts. How can I disable this process so my machine can work and I can get some work done.  Example top:  top - 12:43:48 up  3:02,  3 users,  load average: 6.57, 5.53, 3.33 Tasks: 256 total,   3 running, 253 sleeping,   0 stopped,   0 zombie %Cpu(s):  5.9 us, 16.6 sy,  0.0 ni, 74.7 id,  0.5 wa,  0.0 hi,  2.3 si,  0.0 st KiB Mem:   8080252 total,  7937856 used,   142396 free,   258904 buffers KiB Swap:        0 total,        0 used,        0 free.  4061336 cached Mem    PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND 13509 root     -51   0       0      0      0 S  54.7  0.0   3:29.47 kidle_inject/1 13511 root     -51   0       0      0      0 S  54.1  0.0   3:30.92 kidle_inject/3 13510 root     -51   0       0      0      0 S  48.8  0.0   3:11.60 kidle_inject/2 13508 root     -51   0       0      0      0 S  47.6  0.0   3:08.47 kidle_inject/0