You might want to refer to this blog post:
http://www.activestate.com/blog/2013/06/solomon-hykes-explains-docker

Simply put, Docker does a process isolation leveraging LXC (a kind of lightweight virtualisation built into Linux Kernel). The basic difference between LXC and VMs is that with LXC there is only one instance of Linux Kernel running. The base image OS is used for filesystem, binaries, etc.




I want to write a Bash script that loops over the sha1s of commits output by an invocation of `git log`. However, `git log` gives me much more output than I want:

    commit 0375602ba2017ba8750a58e934b41153faee6fcb
    Author: Mark Amery &lt;markamery@notmyrealemail.com&gt;
    Date:   Wed Jan 1 21:35:07 2014 +0000
    
        Yet another commit message
        
        This one even has newlines.
    
    commit 4390ee9f4428c84bdbeb2fed0a461099a6c81b39
    Author: Mark Amery &lt;markamery@notmyrealemail.com&gt;
    Date:   Wed Jan 1 21:30:19 2014 +0000
    
        Second commit message.
    
    commit bff53bfbc56485c4c1007b0884bb1c0d61a1cf71
    Author: Mark Amery &lt;markamery@notmyrealemail.com&gt;
    Date:   Wed Jan 1 21:28:27 2014 +0000
    
        First commit message.

How can I get `git log` to just output sha1s so that I can loop over them conveniently?

Show sha1 only with git log

What is the &quot;Abbreviation&quot; feature in IntelliJ IDEA Keymap for? [Web help on Keymap](http://www.jetbrains.com/idea/webhelp/keymap.html) is silent about it.

![IntelliJ Keymap abbreviation screenshot][1]


  [1]: http://i.stack.imgur.com/2LjMB.png

What is the IntelliJ IDEA&#39;s Keymap&#39;s abbreviation feature useful for?

It is said that docker is not a VM and containers directly run on the host.

But why do containers need a base image OS ？

If process in containers run on the base image OS , what&#39;s the difference between a VM and docker(only the base image OS can be re-used and kept read-only?)

And why does it boot faster than a VM?

What makes up a base image OS ? kernel , rootfs or both?



docker is not VM , why container need base image OS ？

It is said that docker is not a VM and containers directly run on the host.
But why do containers need a base image OS ？
If process in containers run on the base image OS , what's the difference between a VM and docker(only the base image OS can be re-used and kept read-only?)
And why does it boot faster than a VM?
What makes up a base image OS ? kernel , rootfs or both?

How to write a Base64-encoded image to file?

I have encoded an image to a string using Base64.
First, I read the file, then convert it to a byte array and then apply Base64 encoding to convert the image to a string.

Now my problem is how to decode it.

    byte dearr[] = Base64.decodeBase64(crntImage);
    File outF = new File(&quot;c:/decode/abc.bmp&quot;);
    BufferedImage img02 = ImageIO.write(img02, &quot;bmp&quot;, outF); 

The variable `crntImage` contains the string representation of the image.


Write Base64-encoded image to file

I&#39;ve got some automatic emails that are sent out upon signup completion for my site.

Until recently, they worked fine. Now [Google&#39;s new system is rewriting the images and storing them in it&#39;s cache][1] (supposedly)

However, Google&#39;s new rewriting of my image links are completely breaking them, giving a 500 error and a broken link image.

Lets say my normal image url is:

    http://www.mysite.com/images/pic1.jpg

Google is rewriting this to:

    https://ci5.googleusercontent.com/proxy/vI79kajdUGm6Wk-fjyicDLjZbCB1w9NfkoZ-zQFOB2OpJ1ILmSvfvHmE56r72us5mIuIXCFiO3V8rgkZOjfhghTH0R07BbcQy5g=s0-d-e1-ft#http://www.mysite.com/images/pic1.jpg

However, there is nothing at that URL.

![Email showing image errors][2]

So, either there is something wrong with the links that are being created by Google or the images are just not being uploaded to the googleusercontent server, but I have no idea how to solve the issue.

Im using PHP, the [phpmailer library][3] and a Ubuntu server on Amazon EC2, but Im not sure that is related to the issue.


  [1]: http://blog.wordtothewise.com/2013/12/gmail-deploys-image-proxy-servers/
  [2]: http://i.stack.imgur.com/r6CP5.png
  [3]: http://phpmailer.worxware.com/

Gmail&#39;s new image caching is breaking image links in newsletter

I am trying to achieve something like this:

![this effect][1]

When I hover over an image, I would like to put on that image this dark color with some text and the icon.

I am stuck here. I found some tutorials but they didn&#39;t work out for this case.
Also, another issue -- every image has a different height. The width is always the same.

How can this effect be achieved?


  [1]: http://i.stack.imgur.com/Wtjqz.png

How to make in CSS an overlay over an image?

I know the best way to protect image download is not putting it on internet in the first place.

I assume there is no 100% protection against image download and that if a user can see an image on internet he can with a bit of experience find access to download it.

I am aware of transparent `.gif` or `.png` covering the images or using `background_image` CSS property to protect it and prevent right click download but are there 

**other ways to complicate image download and therefore prevent image download by most users?**

Here is simple code to start with :

&lt;!-- begin snippet: js hide: false console: false babel: false --&gt;

&lt;!-- language: lang-html --&gt;

    &lt;img src=&quot;http://placekitten.com/600/450&quot;&gt;

&lt;!-- end snippet --&gt;

    




  [1]: http://jsfiddle.net/chadocat/nwqdK/2/

Protect image download

How do you convert an image from a path on the user&#39;s computer to a base64 string in C#?

For example, I have the path to the image (in the format `C:/image/1.gif`) and would like to have a data URI like `data:image/gif;base64,/9j/4AAQSkZJRgABAgEAYABgAAD..` representing the `1.gif` image returned.

Convert an image (selected by path) to base64 string

I am going through the topic of virtualization and i am totally sucked up understanding the basic concept, Wikipedia does provide some relevant information, but it is not good enough for me to understand the basic idea. The concept will be of 2 to 3 line, but neither I am able to find them on net, nor on the book. 

I will be pleased if someone gives me a basic understanding of these three types. I am well aware of virtualization and understand it well, but these 3 types... 

What is the difference between Full, Para and Hardware assisted virtualization?

How do you run a program all by itself without an operating system running?
Can you create assembly programs that the computer can load and run at startup, e.g. boot the computer from a flash drive and it runs the program that is on the CPU?

How to run a program without an operating system?

I need to find the OS name and version on Unix/Linux platform. For this I tried following:

1. `lsb_release` utility

2. `/etc/redhat-release` or specific file

But it does not seem to be best solution as LSB_RELEASE support is no longer for RHEL 7.

Is there any way that will work on any Unix or Linux platform?

Best way to find os name and version in Unix/Linux platform

Suppose I know the process ID.  I want to find the process name by its ID, using windows batch script.  How can I do this?

Find Process Name by its Process ID

Ok...I dont know where module `x` is, but I know that I need to get the path to the directory two levels up.

So, is there a more elegant way to do:
    
    import os
    two_up = os.path.dirname(os.path.dirname(__file__))

Solutions for both Python 2 and 3 are welcome!

python: get directory two levels up

This is tricky to word but I have a view controller (vc1) that contains a container view (I&#39;m using storyboards). Within that container view is a navigation controller and a root view controller (vc2).

From within the vc2 how can I get access to vc1? 

Or, how do I pass vc1 to vc2? (baring in mind that I&#39;m using storyboards).

From within a view controller in a container view, how do you access the view controller containing the container?

[Updated1] I have a shell which will change TCP kernel parameters in some functions, but now I need to make this shell run in Docker container, that means, the shell need to know it is running inside a container and stop configuring the kernel. 

Now I&#39;m not sure how to achieve that, here is the contents of `/proc/self/cgroup` inside the container: 

    9:hugetlb:/
    8:perf_event:/
    7:blkio:/
    6:freezer:/
    5:devices:/
    4:memory:/
    3:cpuacct:/
    2:cpu:/docker/25ef774c390558ad8c4e9a8590b6a1956231aae404d6a7aba4dde320ff569b8b
    1:cpuset:/

Any flags above can I use to figure out if this process is running inside a container?

[Updated2]: I have also noticed https://stackoverflow.com/questions/20010199/determining-if-a-process-runs-inside-lxc-docker, but it seems not working in this case, the content in `/proc/1/cgroup` of my container is:

    8:perf_event:/
    7:blkio:/
    6:freezer:/
    5:devices:/
    4:memory:/
    3:cpuacct:/
    2:cpu:/docker/25ef774c390558ad8c4e9a8590b6a1956231aae404d6a7aba4dde320ff569b8b
    1:cpuset:/

No /lxc/containerid

How to check if a process is running inside docker container?

As far as I can tell, anywhere `std::back_inserter` works in an STL algorithm, you could pass an `std::inserter` constructed with `.end()` instead:

    std::copy(l.begin(), l.end(), std::back_inserter(dest_list));
    std::copy(l.begin(), l.end(), std::inserter(dest_list, dest_list.end()));

AND, unlike `back_inserter`, as far as I can tell `inserter` works for ANY STL container!! I tried it successfully for `std::vector`, `std::list`, `std::map`, `std::unordered_map` before coming here surprised.


I thought that maybe it&#39;s because `push_back` could be faster for some structures than `insert(.end())`, but I&#39;m not sure...

That doesn&#39;t seem to be the case for `std::list` (makes sense):

    // Copying 10,000,000 element-list with std::copy. Did it twice w/ switched order just in case that matters.
    Profiling complete (884.666 millis total run-time): inserter(.end())
    Profiling complete (643.798 millis total run-time): back_inserter
    Profiling complete (644.060 millis total run-time): back_inserter
    Profiling complete (623.151 millis total run-time): inserter(.end())

But it does slightly for `std::vector`, though I&#39;m not really sure why?:

    // Copying 10,000,000 element-vector with std::copy.
    Profiling complete (985.754 millis total run-time): inserter(.end())
    Profiling complete (746.819 millis total run-time): back_inserter
    Profiling complete (745.476 millis total run-time): back_inserter
    Profiling complete (739.774 millis total run-time): inserter(.end())

I guess in a vector there is slightly more overhead figuring out where the iterator is and then putting an element there vs just arr[count++]. Maybe it&#39;s that?


But still, is that the main reason?

My followup question, I guess, is &quot;Is it okay to write `std::inserter(container, container.end())` for a templated function and expect it to work for (almost) any STL container?&quot;

&lt;hr&gt;

I updated the numbers after moving to a standard compiler. Here is my compiler&#39;s details:
&lt;br&gt;gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1) &lt;br&gt;
Target: x86_64-linux-gnu

My build command:

    g++ -O0 -std=c++11 algo_test.cc



&lt;hr&gt;

I think [this question asks the second half of my question][1], namely, &quot;Can I write a templated function that uses `std::inserter(container, container.end())` and expect it to work for almost every container?&quot;

The answer there was &quot;Yes, for every container except for `std::forward_list`.&quot; But based on the discussion in the comments below and in [user2746253][2]&#39;s answer, it sounds like I should be aware that this would be slower for `std::vector` than using `std::back_inserter`...

Therefore, I might want to specialize my template for containers using `RandomAccessIterator`s to use `back_inserter` instead. Does that make sense? Thanks.


  [1]: https://stackoverflow.com/q/23360656/751061
  [2]: https://stackoverflow.com/users/2746253/user2746253

What&#39;s the benefit of std::back_inserter over std::inserter?

I&#39;d like to create the following infrastructure flow:

![](https://www.lucidchart.com/publicSegments/view/54c49ac3-3218-4243-8e47-43d90a005586/image.png)

How can that be achieved using Docker?

How to SSH into Docker?

This is a very basic question, but I&#39;m struggling a bit and would like to make sure I understand properly.

After a container is started from an image and some changes done to files within (i.e.: some data stored in the DB of a WebApp running on the container), what&#39;s the appropriate way to continue working with the same data between container stop and restart?

Is my understanding correct that once the container is stopped/finished (i.e.: exit after an interactive session), then that container is gone together with all file changes?
So if I want to keep some file changes I have to commit the state of the container into a new image / new version of the image?

Do docker containers retain file changes?

I am using `docker run /bin/bash` to develop my container and every time I want to use `Ctrl+p` in a terminal or in emacs, I have to type it twice, since docker uses it to detach from a container (`Ctrl+p` `Ctrl+q`).

How can I change `Ctrl+p` to something else more convenient that is not used in emacs or in a terminal setting?

docker change Ctrl+p to something else?

So I have 3 ports that should be exposed to the machine&#39;s interface. Is it possible to do this with a Docker container?

How can I expose more than 1 port with Docker?

I have a container that is running the Apache service in the foreground. I would like to be able to access the container from another shell in order to &quot;poke around&quot; inside it and examine the files. At the moment, if I attach to the container, I am left looking at the Apache daemon and cannot run any commands.

Is it possible to attach another tty to a running container? Possibly, I can take advantage of the fact that Docker is actually just wrapping around LXC containers? I have tried `sudo lxc-console -n [container-id] -t [1-4]` but it appears that only one tty is made available and that is the one running the apache daemon. Perhaps there is a way to enable multiple lxc consoles during the build?

I would rather **not** configure and build the container with an openssh service if possible.

How to enter in a Docker container already running with a new TTY

I would like to make my `docker containers` aware of their configuration, the same way you can get information about EC2 instances through metadata.

I can use (provided `docker` is listening on port `4243`)

    curl http://172.17.42.1:4243/containers/$HOSTNAME/json

to get some of its data, but would like to know if there is a better way at least the get the full ID of the container, because `HOSTNAME` is actually shortened to 12 characters and docker seems to perform a &quot;best match&quot; on it.

Also, how can I get the external IP of the docker host (other than accessing the EC2 metadata, which is specific to AWS)
 

How can I get Docker Linux container information from within the container itself?

When running a service inside a container, let&#39;s say mongodb, the command 
    
    docker run -d myimage

will exit instantly, and return the container id.
In my CI script, I run a client to test mongodb connection, right after running the mongo container.
The problem is: the client can&#39;t connect because the service is not up yet.
Apart from adding a big ```sleep 10```in my script, I don&#39;t see any option to wait for a container to be up and running.

Docker has a command ```wait``` which doesn&#39;t work in that case, because the container doesn&#39;t exist.
Is it a limitation of docker?

Content Type	Original Author	Original Content on Stackoverflow
Question	cola	View Question on Stackoverflow
Solution 1 - Image	ondrasek	View Answer on Stackoverflow

docker is not VM , why container need base image OS ？

Image Problem Overview

Image Solutions

Solution 1 - Image

What is the IntelliJ IDEA's Keymap's abbreviation feature useful for?

Show sha1 only with git log

Attributions