Thursday 30 October 2014

Docker design doc1


A sample docker design doc, how we can implement docker in the production environment. Will update other docker command later in the blog.

The ports are just for example. Note: we can run the keepalived and haproxy on the same server where docker is running, just for simplicity I draw at different server.

Following image's original pdf link:
https://drive.google.com/file/d/0B02LZ59YLdSdaTBlVGdmX0RlWU0/view?usp=sharing



Thursday 23 October 2014

vimrc

my quick ~/.vimrc

set hlsearch
syntax enable
set tabstop=4
set softtabstop=4
set expandtab
set showcmd
set cursorline
filetype indent on
set showmatch
set incsearch

Wednesday 8 October 2014

nc - [ netcat ] - unix command

nc

0)

Copy a complete directory [ lets say a mysql data " but you should not take a running mysql data " ]

Go to destination computer's destination EMPTY directory where you want to dump the data and run:[[[  nc -l 3333 | tar -zxvf -   ]]] - Note you can use any free port at the place of 3333

now go to the source computer and type: [[[ tar cvz <directory> | nc destination_hostname 3333 ]]]

1)

Destination host:

nc -lp [3333] > [file]     [ listen to port 3333 and what ever comes from that port put that to <<file>>


Sources host:
cat <<file>> | nc -w 1 IP <<3333>>   [ to transfer a <<file>> of course host with netcat with having timeout of 1 sec " -w 1 " and on port of 3333


2)
man nc:

-l      Used to specify that nc should listen for an incoming connection rather than initiate a connection to a remote host.  It is an error to use this option in conjunction
             with the -p, -s, or -z options.  Additionally, any timeouts specified with the -w option are ignored.

-p source_port
             Specifies the source port nc should use, subject to privilege restrictions and availability.  It is an error to use this option in conjunction with the -l option.


-w timeout
             If a connection and stdin are idle for more than timeout seconds, then the connection is silently closed.  The -w flag has no effect on the -l option, i.e. nc will
             listen forever for a connection, with or without the -w flag.  The default is no timeout.


3)
CLIENT/SERVER MODEL
     It is quite simple to build a very basic client/server model using nc.  On one console, start nc listening on a specific port for a connection.  For example:

           $ nc -l 1234

     nc is now listening on port 1234 for a connection.  On a second console (or a second machine), connect to the machine and port being listened on:

           $ nc 127.0.0.1 1234

     There should now be a connection between the ports.  Anything typed at the second console will be concatenated to the first, and vice-versa.  After the connection has been set
     up, nc does not really care which side is being used as a ‘server’ and which side is being used as a ‘client’.  The connection may be terminated using an EOF (‘^D’).


4)
DATA TRANSFER
     The example in the previous section can be expanded to build a basic data transfer model.  Any information input into one end of the connection will be output to the other
     end, and input and output can be easily captured in order to emulate file transfer.

     Start by using nc to listen on a specific port, with output captured into a file:

           $ nc -l 1234 > filename.out

     Using a second machine, connect to the listening nc process, feeding it the file which is to be transferred:

           $ nc host.example.com 1234 < filename.in

     After the file has been transferred, the connection will close automatically.


5)
TALKING TO SERVERS
     It is sometimes useful to talk to servers “by hand” rather than through a user interface.  It can aid in troubleshooting, when it might be necessary to verify what data a
     server is sending in response to commands issued by the client.  For example, to retrieve the home page of a web site:

           $ echo -n "GET / HTTP/1.0\r\n\r\n" | nc host.example.com 80

     Note that this also displays the headers sent by the web server.  They can be filtered, using a tool such as sed(1), if necessary.

     More complicated examples can be built up when the user knows the format of requests required by the server.  As another example, an email may be submitted to an SMTP server
     using:

           $ nc localhost 25 << EOF
           HELO host.example.com
           MAIL FROM: <user@host.example.com>
           RCPT TO: <user2@host.example.com>
           DATA
           Body of email.
           .
           QUIT
           EOF



6)
PORT SCANNING
     It may be useful to know which ports are open and running services on a target machine.  The -z flag can be used to tell nc to report open ports, rather than initiate a con-
     nection.  For example:

           $ nc -z host.example.com 20-30
           Connection to host.example.com 22 port [tcp/ssh] succeeded!
           Connection to host.example.com 25 port [tcp/smtp] succeeded!

     The port range was specified to limit the search to ports 20 - 30.

     Alternatively, it might be useful to know which server software is running, and which versions.  This information is often contained within the greeting banners.  In order to
     retrieve these, it is necessary to first make a connection, and then break the connection when the banner has been retrieved.  This can be accomplished by specifying a small
     timeout with the -w flag, or perhaps by issuing a "QUIT" command to the server:

           $ echo "QUIT" | nc host.example.com 20-30
           SSH-1.99-OpenSSH_3.6.1p2
           Protocol mismatch.
           220 host.example.com IMS SMTP Receiver Version 0.84 Ready

7)
EXAMPLES
     Open a TCP connection to port 42 of host.example.com, using port 31337 as the source port, with a timeout of 5 seconds:

           $ nc -p 31337 -w 5 host.example.com 42

     Open a UDP connection to port 53 of host.example.com:

           $ nc -u host.example.com 53

     Open a TCP connection to port 42 of host.example.com using 10.1.2.3 as the IP for the local end of the connection:

           $ nc -s 10.1.2.3 host.example.com 42

     Create and listen on a Unix Domain Socket:

           $ nc -lU /var/tmp/dsocket

     Connect to port 42 of host.example.com via an HTTP proxy at 10.2.3.4, port 8080.  
This example could also be used by ssh(1); see the ProxyCommand directive in ssh_config(5)
     for more information.

           $ nc -x10.2.3.4:8080 -Xconnect host.example.com 42


8) Minimal web-server example:
You can set up netcat to act as a very basic webserver which can just serve one file:
while `netcat -lp 8080 -c 'echo HTTP/1.0 200 OK';echo;cat file`;do;done


9) local port forwarding:
This command would forward every request on port 8080 to port 80:
while `netcat -lp 8080 -c 'netcat localhost 80'`;do;done


10) getting telnet command output using nc: [ example memcache ]

printf 'stats\n' | nc 127.0.0.1 11211 | grep limit_maxbytes