Ubuntu sets the environment variable and takes effect immediately (take Ubuntu12.04 as an example)

The Ubuntu Linux system contains two types of environment variables: System environment variables and user environment variables. System environment variables are valid for all system users, and user environment variables are only valid for current users. Modifying user environment Variables

User environment variables are usually stored in the following file:

~/.profile

~/.bash_profile or ~./bash_login.

~/.bashrc

The above files are not recommended for use in Ubuntu 10.0 versions. System Environment Variables

System environment variables are generally saved in the following file:

/etc/environment

/etc/profile

/etc/bash.bashrc

/etc/profile and/ETC/BASH.BASHRC are not recommended for use in Ubuntu version 10.0. Adding environment Variables

If you want to add a path to the $path, you can do so (modify/etc/profile) as follows:

sudo vi/etc/profile

In the inside add:

java_home=/usr/jdk1.6.0_25
export java_home
path= $PATH: $JAVA _home/bin
export PATH
classpath=.:$ Java_home/lib
Export CLASSPATH

You can add multiple paths of your own, separated by colons. When the environment variable is changed, it will take effect the next time the user logs on, and if you want to take effect immediately, execute the following statement:

Source/etc/profile

It should be noted that it is best not to put the current path "./" Into the path, which may be subject to unexpected attacks.

Other files are modified in the same way, it should be noted that/etc/environment does not need to use export to set environment variables, other profile files need.

A more detailed description can be referred to here.

Of course, if you want to use the text Editing tool to modify the environment variables, you can use the root permission to open the Modify save directly with the text editor

You can also use the normal user rights to copy files to the desktop, and so on, with root rights cover back

#/etc/profile:system-wide Profiles file for the Bourne shell (SH (1))
 # and Bourne compatible shells (Bash (1), Ksh (1) , Ash (1), ...).
     
 if[-D/ETC/PROFILE.D]; Then
   fori in/etc/profile.d/*.sh;do
     if[-R $i] then
       . $i
     fi
   done
     
 java_home=/usr/hadoop/ jdk1.6.0_25
 export java_home
 path= $PATH: $JAVA _home/bin
 export PATH
 classpath=.: $JAVA _home/lib
 export CLASSPATH
     
   unseti
 fi
     
 if["$PS 1"]; then
   if["$BASH"] then
     # the file BASH.BASHRC Already sets the default PS1.
     # ps1= ' \h:\w\$ '
     if[-F/ETC/BASH.BASHRC] then
       ./etc/bash.bashrc
     fi
   else
     if["' id-u '"-eq0] ; Then
       ps1= ' # '
     else
       ps1= ' $ '
     fi
 fi fi

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