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JVM Class Loading

classloader Configuration options Jvm/jre
bootstrap META-INF/ Class-Path of above jars JRE

System property: java.ext.dir. Default: $JAVA_HOME/jre/lib/ext

META-INF/ Class-Path of above jars

how to split and join large files


best and simplest way to split large file and join files

1. split large file in chunk of 1GB

split -b 1000m

above command will create files

unix how to change file date and timestamp


There are several several ways we can control the file timestamp on unix systems, touch command is useful to modify file to specific timestamp for:

1. access time

2. modified time

usage: touch option filename(s)


-a = modify only access time

-m = modify only modified time

-r = reference copy the timestamp from file1 to file2

-d = add specifc timestamp to file

-t = add specific timestamp same as -d option but with different format 

citrix receiver error configuration manager cannot be initialized

Citrix Receiver is getting an error "configuration manager cannot be initialized" when installing , re-installing on windows. 
Follow these steps to cleanup the registery before installing citrix receiver:
1. Start->Run->regedit
2. Edit->Find the following text
3. Right click and delete every occurance of this register

Apple MAC change or switch java version

By default JAVA is installed on mac at /System/Library/Java/JavaVirtualMachines
1. export JAVA_HOME and udpate PATH


$ export JAVA_HOME=$(/usr/libexec/java_home -v 1.7) ; export PATH=$JAVA_HOME/bin:$PATH


2. Check Java version from commandline



$ java -version

java version "1.7.0_17"

Java(TM) SE Runtime Environment (build 1.7.0_17-b02)

openssh ssh public and private keys setup and permission

In general one unix node can access another node, this can be configured using a common unix account on all the nodes with same username, password could be different on each machine, for security we prefer to keep access at user level on each node. Generally we provide sudo access for this user to higher level access on machines.
Step 1: Create account with same username on all unix machines
Step 2: Verify SSH  installation
- verify if SSH is installed on your machines. If SSH is not installed, you can install from

Python HTTP Basic Authentication Program

Python  HTTP Basic Authentication Program



Self Signed Certification Bypass keystore and validations

Ping SSL command line utilty:

New Line Characters at end of line

awk '{sub("$","\r\n"); printf("

Pattern Matching metacharacter Definitions

Pattern Matching metacharacter Definitions
Char. Definition
\ Use before any of the following characters to escape or null the meaning or it. \* \. \$ \+ \[ \]
^ Start matching at this point
$ End point of the match


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