I using Redhat/Centos 6.5.  I am starting up the system and it already has environment variables set and is already running processes when it starts up.  My questions:    Where do these environment variables get set? Where do these processes get set and how do I know what is running?
I have a Linux instance that I set up some time ago.  When I fire it up and log in as root there are some environment variables that I set up but I can't remember or find where they came from.     I've checked ~/.bash_profile, /etc/.bash_rc, and all the startup scripts.  I've run find and grep to no avail.   I feel like I must be forgetting to look in some place obvious. Is there a trick for figuring this out?
Turning a cipher into a hashing function This is theoretical question. I'd like to know if it's possible (and what are eventually the consequences), not that I'm going to do it in one of my projects. ;)  The first hashing functions created were based on a symmetric cipher (just like the first Unix crypt was based on DES). The idea was simple. Use the password as key to encode a constant.  I'd like to know if it's still possible to convert any modern symmetric cipher into a hashing function (and second question: into a cryptographic hashing function). Is it possible (easier) to guess the key, when you have an encoded and decoded messages? Using (or not) the word "to" in a sentence ending with "be able" How do I resolve unmet dependencies after adding a PPA? Occasionally, when I'm installing stuff, I get an error like the following:  Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  package1 : Depends: package2 (&gt;= 1.8) but 1.7.5-1ubuntu1 is to be installed E: Unable to correct problems, you have held broken packages.   How can I resolve this? How do I run wireshark, with root-privileges? A standard installation of Wireshark doesn't give the program permission to access the network interface.   I suppose I have to run the program with sudo, but do not know how to add it to the icon - if that's the way to do it. How to respond to "How much funding will you bring?" as an interview question for a faculty job? Pokemon Go: Can't log in? Are everyone unable to log in right now? 2016 July 16. Where I live none can log in to the servers at the moment, and it all happened after the sudden release of the game in my country.   As I understand the game was recently released in 26 countries, so I guess they have problems and had the servers go offline in order to fix the issues. Apply for a Korean visa in Japan I'm a Vietnamese citizen and currently living in Japan. Can I apply for a South Korea tourist visa at the Korean embassy in Japan, or must I do it at the Korean embassy back in Vietnam? WinForms Global Exception Handling? How do I access $HOME/storage Termux directory on Android Pie with a GUI File Explorer?  In Termux I print the working directory with pwd and it shows $HOME/storage as:  /data/data/com.termux/files/home   My internal storage looks like this:  . ├── Alarms ├── Android |   ├──data |   |  ├── ... |   |  ├── com.termux |   |  |   └── files |   |  |       └── 0 items |   |  └── ... |   └── ... ├── DCIM ├── Download └── ...   My external storage looks like this:  . ├── Android |   ├──data |   |  ├── ... |   |  ├── com.termux |   |  |   └── files |   |  |       └── 0 items |   |  └── ... |   └── ... └── LOST.DIR   Neither my internal storage, nor my sd card, contain a /data/ directory at the root level. Where is this /data/ directory? For that matter, where is the root /storage/ directory? Where is the root /emulated/ directory? Where are any of these directories and why cant I access any of them? Projection on the hyperplane $H: \sum x_i=0$ We are all told at school water vapour and carbon dioxide are the top two greenhouse gases, and that they absorb thermal infra red radiation, trap heat and warm up the Earth. My question is how do they do that? Why can't Oxygen or Nitrogen or any other gas not absorb infra red radiation as well as water vapour or CO2? was closed as "Not constructive" a little while ago by CasperOne. I'm not here to argue about the closure; in fact, I'm forced to agree that, as it stands, the question is explicitly a polling question and eligible to be closed for that reason.  I'd like to see it preserved, however; it's got a fair bit of useful in-depth information for ObjC/Cocoa developers on the "singleton" topic.* It's also (possibly more importantly) a great duplicate target -- have a look at the list of linked questions. I want to try to stave off deletion, and hopefully get it reopened.** (I did vote for reopening, but it expired.)  My thought is to edit the question itself into a "constructive" form, but after spending some time pondering how to do so, I'm not crazy about any of the ideas that I've come up with. Essentially they all involve reworking the question to fit the answers:   Rewrite the question so that the accepted answer fits exactly. "I've got this singleton implementation, but I really want the creation to happen earlier in my app's execution. How can I make that happen?" This is artificial and (in my opinion) doesn't make a particularly good question. Make the question still general, but more concrete and focused on the implementation give in the body. "What are the pitfalls associated with this singleton creation procedure? Are there other features that my singleton should have?" This is still skirting the border of discussion->NC, and none of the answers really respond to this exactly. Remove the implementation from the question and just ask for the "best" implementation. This obviously requires coming up with stringent criteria for "best", and, while it would preserve the relationship between the Q and A's best, might not even move it out of NC territory.   I'm looking for suggestions of ways to re-write this so that it can stick around. Alternatively, if you think I should just be advocating for a historical lock, say so.   If you think my basic premise is faulty and don't think the question should be preserved at all, I respectfully request that you just downvote me instead of answering -- I'd prefer not to turn this into an argument about the merits of the question, and I definitely don't want it to become a(nother) "deletionist"/"inclusionist" skirmish (and I am not infrequently ).    *Quite a bit of it unfortunately in comments.  **Historical locking would also be an acceptable solution to me, but it doesn't seem to fit the "controversial" criterion. Proving a binomial sum identity $\sum _{k=0}^n \binom nk \frac{(-1)^k}{2k+1} = \frac{(2n)!!}{(2n+1)!!}$ Is there a simple way of proving that $\text{GL}_n(R) \not\cong \text{GL}_m(R)$? Letting $\mathbb{F}_{1}$ and $\mathbb{F}_{2}$ be fields, and letting $n \geq 3$ and $m$ be natural numbers, it is known that $\text{GL}_{m}(\mathbb{F}_{1})$ and $\text{GL}_{n}(\mathbb{F}_{2})$ are elementarily equivalent if and only if $m=n$ and $\mathbb{F}_{1} \equiv \mathbb{F}_{2}$ (as proven in "Elementary Properties of Linear Groups" in the collection "The Metamathematics of Algebraic Systems — Collected Papers: 1936–1967").  So, given a field $\mathbb{F}$, if $n \neq m$, then $\text{GL}_{m}(\mathbb{F}) \not\equiv \text{GL}_{n}(\mathbb{F})$, and thus $\text{GL}_{m}(\mathbb{F}) \not\cong \text{GL}_{n}(\mathbb{F})$.  Letting $R$ be a commutative ring (with unity), and letting $n, m \in \mathbb{N}$ be such that $n \neq m$, is there a simple "algebraic" way of proving that $\text{GL}_{m}(R)$ and $\text{GL}_{n}(R)$ are not isomorphic (as groups)? Is there a simple group-theoretic way of showing that $\text{GL}_{m}(\mathbb{F}) \not\cong \text{GL}_{n}(\mathbb{F})$ for a field $\mathbb{F}$?  Certain special cases of this problem trivially hold, for example in the case whereby $\mathbb{F}$ is finite, in which case $|\text{GL}_{m}(\mathbb{F})| \neq |\text{GL}_{n}(\mathbb{F})|$. I would like to create a minecraft server for me and and my boyfriend to play on.  How do I set it up? Do I need any additional software? Do you have some links to walkthroughs or tutorials?  I have tried to set this up a few times but have failed every time. I have notice some sites have the same form for login, register and forgotten password.  Below the form you have 3 buttons    i forgot my password register log me in   What are the pros and cons on using this approach and which version would you go for. What is your favorite method to handle errors in Bash?  The best example of handling errors I have found on the web was written by William Shotts, Jr at .   He suggests using the following function for error handling in Bash:  #!/bin/bash  # A slicker error handling routine  # I put a variable in my scripts named PROGNAME which # holds the name of the program being run.  You can get this # value from the first item on the command line ($0).  # Reference: This was copied from &lt;http://www.linuxcommand.org/wss0150.php&gt;  PROGNAME=$(basename $0)  function error_exit {  #   ---------------------------------------------------------------- #   Function for exit due to fatal program error #       Accepts 1 argument: #           string containing descriptive error message #   ----------------------------------------------------------------       echo "${PROGNAME}: ${1:-"Unknown Error"}" 1&gt;&amp;2     exit 1 }  # Example call of the error_exit function.  Note the inclusion # of the LINENO environment variable.  It contains the current # line number.  echo "Example of error with line number and message" error_exit "$LINENO: An error has occurred."   Do you have a better error handling routine that you use in Bash scripts? How do I remap the keys on my keyboard? I broke my laptop and had to buy a new one with a new keyboard that I am struggling to get familiar with, especially with the keys like home, page-up, page-down and end, which aren't standardized at all.  I found myself doing this for like the 5th time in the last several years, and I think it is really annoying.   Is there an app that can reliably map one key to another?  By reliably I mean that key mapping works with Shift, Alt, and other modifiers.  UPDATE  Windows 7, Samsung Chronos 7 How do you create a simple, custom rule using the jQuery Validate plugin (using ) that doesn't use a regex?  For example, what function would create a rule that validates only if at least one of a group of checkboxes is checked? What is `^M` and how do I get rid of it? When I open the file in Vim, I see strange ^M characters.  Unfortunately, the world's favorite search engine does not do well with special characters in queries, so I'm asking here:   What is this ^M character? How could it have got there? How do I get rid of it?