Maiar's Vault

If you want to stop one node in a hadoop cluster run the following two commands. /usr/local/hadoop/bin/hadoop-daemon.sh --config /usr/local/hadoop/bin/../conf stop datanode /usr/local/hadoop/bin/hadoop-daemon.sh --config /usr/local/hadoop/bin/../conf stop tasktracker

Here is how to stop a single tasktracker node in a hadoop cluster. /usr/local/hadoop/bin/hadoop-daemon.sh --config /usr/local/hadoop/bin/../conf stop tasktracker

The normal command you are shown shutsdown the entire cluster. To shutdown a single datanode for maintenance run the following command. /usr/local/hadoop/bin/hadoop-daemon.sh --config /usr/local/hadoop/bin/../conf stop datanode

test if variable exists in perl Just use the boundp function (setq x 1) => 1 (boundp 'x) => true

In most cases just use the perl function defined if(defined $somevar) { print "This variable exists\n"; }

This article describes it best on how to get Ad Bright working on Blogger http://www.mydigitallife.info/2007/09/21/trick-to-add-adsense-adbrite-and-other-javascript-ad-code-directly-to-blogger-html-template/ < – < > – > Above two is enough to make Google AdSense works in Blogger template. For other scripts, such as AdBrite ad code, you will need to replace more characters such as those listed below. & = & ” = "

Here is a great article about scalable analytics and a hybrid system called HadoopDB http://dbmsmusings.blogspot.com/2009/07/announcing-release-of-hadoopdb-longer.html HadoopDB can be found at http://db.cs.yale.edu/hadoopdb/hadoopdb.html Footnote mentions of open source column-store database systems such as MonetDB and Infobright

If you haven't used rsync yet you should. It's a great tool for mirroring http://www.samba.org/rsync/

This is a great Opensource Mac IPSec VPN Software package, the commercial great is VPNTracker http://www.lobotomo.com/products/IPSecuritas/index.html

if [ ! -d $directory ]; then echo "Directory does not exist" else echo "Directory does exist" fi

if [ -d $directory ]; then echo "Directory exists" elif [ -d $directory2 ]; then echo "Directory2 exists" else echo "Directory does not exists" fi

Here is how to tell if a directory exists in bash. if [ -d 'somedirectory' ]; then #some bash commands fi

http://perldoc.perl.org/Getopt/Long.html I love perl's getopt example, it's very easy to use and to the point. Here is the standard example from the documentation use Getopt::Long; my $data = "file.dat"; my $length = 24; my $verbose; $result = GetOptions ("length=i" => \$length, # numeric "file=s" => \$data, # string "verbose" => \$verbose); # flag All you need to do now to check if your variable is is set and use it Example: if(! defined $data) { die "Throwing error because required field isn't set."; }

To run a command in vim from the current line till the end of the file you do the following .,$d .,${command here} .,$y

Vim how to do command on current line plus 1 2 etc lines .,+1s/^/text/ #command on one line .,+2dd #command on two lines .,+3>> #command on three lines So the syntax is .,+{number of lines}{vim command}

How to set the selected option from presence of a variable is this simple. <option value="somevalue" <?= ? array_key_exists('variablename', $_GET) "selected" : "" ?>>Display value </option>

Testing to see if a php get variable is set is a very easy thing to do. All you need is this one line. array_key_exists('nameofgetvariable', $_GET)

To add the default option to a html pull down option.

In vim to add text to the beginning of every line is easy. vim filename :%s/^/texttoadd/ Be careful with the texttoadd because you might have to escape certain characters.

If you have a mysql client install you can run commands from the command line on a remote mysql server running the following command. Remember you can use single quotes safely between the double quotes. mysql -uusername -ppassword -h192.168.1.1 dbname -e "select * from dual ;" ;

Run the following command This is a perl one liner that will append text to the beginning of a file. PS It edits the file in place so please backup your file first before running. perl -i -ple 'print q{PUTYOURTEXTHERE} if $. == 1; close ARGV if eof' myfilename

This example will first cd into the directory that you want to start searching from. It will descend into each sub directory counting the number of entries(files or dirs) and print it out to the command line. The last step sort the output. cd /mydir; perl -MFile::Find -e 'find({wanted=>sub {},no_chdir=>1,postprocess=>sub {my $wc = `ls $File::Find::dir | wc -l`;chomp($wc);print "$wc\t$File::Find::dir\n"; }}, ("."));' | sort -n

The semi colon aka -> ; ; is the lisp comment character example: (print "Hello World\n") ; this prints the standard Hello World