Linux performance tools graph

Thanks to http://www.brendangregg.com/linuxperf.html

Creating maven repository from Gradle dependencies (upload on local artifactory)

1)      Take back-up of $USER_HOME/.m2/repository  folder and perform 'gradle install'

>> gradle install

2)      ‘gradle install’ will build file ‘build/poms/pom-default.xml’ 
        Note: Skip the gradle install step, if you already have 'pom' file.

3)      To download the all the dependencies with the following  Maven command using ‘pom-default.xml’.  (Internet proxy settings must be correctly set in $USER_HOME/.m2/settings.xml )

>> mvn dependency:copy-dependencies -Dmdep.copyPom=true -Dmdep.useRepositoryLayout=true -Dmdep.addParentPoms=true

Note: Need maven-dependency-plugin:2.9 or above for “addParentPoms” to work.

4)      The entire dependency files will be downloaded in $USER_HOME/.m2/repository, which can be directly uploaded into the artifactory.

    

Parameter substitution in Linux shell

 Following the  table of parameter substitution in shell based on if parameter is set / empty (‘null’) / or unset:

+--------------------+----------------------+-----------------+-----------------+

|                    |         Set          |   Empty('null') |      Unset      |

+--------------------+----------------------+-----------------+-----------------+

| ${parameter:-word} | substitute parameter | substitute word | substitute word |

| ${parameter-word}  | substitute parameter | substitute null | substitute word |

| ${parameter:=word} | substitute parameter | assign word     | assign word     |

| ${parameter=word}  | substitute parameter | substitute null | assign word     |

| ${parameter:?word} | substitute parameter | error, exit     | error, exit     |

| ${parameter?word}  | substitute parameter | substitute null | error, exit     |

| ${parameter:+word} | substitute word      | substitute null | substitute null |

| ${parameter+word}  | substitute word      | substitute word | substitute null |

+--------------------+----------------------+-----------------+-----------------+

${parameter-substitute_value} --> Use substitute only if parameter is 'not set' 

${parameter:-substitute_value} --> Use substitute when parameter is 'not set' and also when parameter is set but empty ('null')

Adding environment from external/workspace file into the Jenkins pipeline

// Reading workspace inside pipeline script file using 'readProperties or readFile', 

def props = readProperties file: 'tempFiles/env.properties'

// Adding environment into the Jenkins:
props.each { name, val ->

   println "Exporting to Jenkins environment: " + name + "="  + val

   env."$name" = "$val"

}

Steganography - hiding data within JPG file

The data file must be a ZIP file ('data.zip') and image.jpeg is a image file.

# The data file must be a ZIP file ('data.zip') and 'image.jpeg' is a image file.

>> cat image.jpeg data.zip  > test.jpg

To see the content of jpg having image + data file

>> unzip -t test.jpg

To extract content from jpg having image + data file

>> unzip test.jpg

Defrag MYSQL database

Over a period of time, "mysql" tables usually get fragmented. It degrades the performance of "mysql-server" significantly.

You may also find it worth your while to defragment your database tables regularly if you are using VARCHAR fields: these variable-length columns are particularly prone to fragmentation.

To defragment tables manually from command-line using mysqlcheck

Run the following command by replacing USER & PASS values:

mysqlcheck -Aos -u <user> -p <password>

Parallelise your build using make

If you're running a multiprocessor system (SMP) with a moderate amount of RAM, you can usually see significant benefits by performing a parallel make when building code. Compared to doing serial builds when running make (as is the default), a parallel build is a vast improvement. To tell make to allow more than one child at a time while building, use the -j switch:

make -j4; make -j4 modules