Vivek H Nayee Linux commands

JAVA Installation on Linux.

noreply@blogger.com (Vivek H Nayee) — Sun, 17 May 2015 18:01:00 +0530

Easy steps for installing JAVA in Linux:

For JAVA you need to install jdk.

You can get the jdk in different ways depending on the OS you are using.

Also need to say that “openjdk” & “oracle java” refers to different things for installation.

Depending on your requirement you can install any one or both.

For various flavors of linux refer below passage: install the “openjdk” package.

JDK 7

Debian, Ubuntu, etc.

On the command line, type:

$ sudo apt-get install openjdk-7-jre

The openjdk-7-jre package contains just the Java Runtime Environment. If you want to develop Java programs then install the openjdk-7-jdk package.

Fedora, Oracle Linux, Red Hat Enterprise Linux, etc.

On the command line, type:

$ su -c "yum install java-1.7.0-openjdk"

The java-1.7.0-openjdk package contains just the Java Runtime Environment. If you want to develop Java programs then install the java-1.7.0-openjdk-develpackage.

JDK 6

Debian, Ubuntu, etc.

On the command line, type:

$ sudo apt-get install openjdk-6-jre

The openjdk-6-jre package contains just the Java Runtime Environment. If you want to develop Java programs then install the openjdk-6-jdk package.

Fedora, Oracle Linux, Red Hat Enterprise Linux, etc.

On the command line, type:

$ su -c "yum install java-1.6.0-openjdk"

The java-1.6.0-openjdk package contains just the Java Runtime Environment. If you want to develop Java programs then install the java-1.6.0-openjdk-develpackage.

BSD Port

For a list of pointers to packages of the BSD Port for DragonFly BSD, FreeBSD, Mac OS X, NetBSD and OpenBSD, please see the BSD porting Project's wiki page.

Now you can check the installed package by issuing a command:

“Java –version”. It will show you the version and the java you have installed in your system.

[P.S: “-” is single hyphen prefix to version.]

For installing the Oracle based java you can directly download the binary file from the official site of oracle. Based on the taste of installation as per user you can download the rpm or any file.

[In case of reference for downloading the source jdk SE files: http://www.oracle.com/technetwork/java/javase/downloads/index.html ]

Here I refer to a binary package of jdk as I find it very easy for installation process. Also the “tar.gz” will work. All you need is the extracted folder.

For bin file:

Go to the downloaded directory of bin file. Mostly “.bin” files are executable, but you can check it using the command “ls -la” and see the permissions. If it is not executable, change the privileges by executing the command

$ chmod +x jdkfilename.bin

Then execute the file using command:

$ su –c “sh jdkfilename.bin”

You will get the extracted folder under the present working directory.

[For ubuntu you have to use “sudo” instead of “su -c”.]

For tar.gz file:

Go to the downloaded directory of bin file. Execute the following command to extract the contents.

$ su –c “tar –zxvf jdkfilename.tar.gz”

You will get the extracted folder under the present working directory.

Once you have the extracted directories copy that jdk directory to place where you want to run java from. Here I am keeping it in the “/usr/local/”.

Also check first the bin folder in the extracted folder of jdk. Then we need to change the default java location for system using the command:

(I am writing the following commands assuming you have logged in as root)

Step 1:

# update-alternatives –install “java” “/usr/local/jdk1.6.0_31/bin/java” 1

[

If you already have openjdk installed in the system you can write as follows

# update-alternatives –install “/usr/bin/java” “java” “/usr/local/jdk1.6.0_31/bin/java” 1

]

The main aim is set and run the default java as the one which we have installed in the directory.

Step 2:

Now we set the new java as default by using command:

# update-alternatives –set java /usr/local/jdk1.6.0_31/bin/java

[P.S: “--” is two hyphen prefix to “set” & “install”.]

Step 3:

Similar to above steps we have to update the javac alternatives as follows.

# update-alternatives –install “javac” “/usr/local/jdk1.6.0_31/bin/javac” 1

[

If you already have openjdk installed in the system you can write as follows

# update-alternatives –install “/usr/bin/javac” “javac” “/usr/local/jdk1.6.0_31/bin/javac” 1

]

Now set the javac alternative with:

# update-alternatives –set javac /usr/local/jdk1.6.0_31/bin/javac

Now you can check the installed version by executing the command:

Java –version

Javac –version

Now to update and switch between two versions of java you have installed, use the following command:

# update-alternatives –config java

This will allow you to switch between the existing java versions in you system.

[note the 2 “-” hyphens prefix to “config” in above command]

Now for setting the environment variables you can edit the “environment” file or the “.bash_profile” as follows.

[Location & name of environment file varies as per os, generally its “/etc/environment” & “/.bash_profile”.]

Using “vi” editor you can edit the files.

[use command:

# cd

#vi .bash_profile

]

Add the lines:

JAVA_HOME=/usr/local/jdk1.6.0_31

JRE_HOME=/usr/local/jdk1.6.0_31/jre

Path=……..$JAVA_HOME:$JRE_HOME

And you are ready to go.

The environment variable changes are reflected automatically and dynamically, but if they are not reflected then just log out and log in again.

Review: Using the “openjdk” is very easy. Just execute the “yum install” command to install the package. Or you can also use the graphical tool for desktop version. [example “synaptic software manager” in ubuntu.]

If you are using Oracle version, just download the “bin” or “tar.gz” file. Extract it, copy it the desired location. Then update the alternatives & set the environment variables.

You are ready to roll with the java now.

Vivek H Nayee.

Linux administration basic commands

noreply@blogger.com (Vivek H Nayee) — Tue, 28 Apr 2015 18:10:00 +0530

Linux Newbie Administrator Guide

A walk through of the commands we use most often in practical environment for Linux.

Press <Tab> to see the listing of all available command (on your PATH).

On my small home system, it says there are 2595 executables on my PATH.

Many of these "commands" can be accessed from your favourite GUI front-end (probably KDE or Gnome) by clicking on the right menu or button.

They can all be run from the command line. Programs that require GUI have to be run from a terminal opened under a GUI.

Legend:

<> = single special or function key on the keyboard. For example <Ctrl> indicates the "control" key.

italic = name of the file or variable you probably want to substitute with your own.

fixed width = in-line Linux commands and filenames.

Special Note, Must Read:

LINUX IS CASE-SENSITIVE.

For example: Apache, APACHE and aPache are three different commands.

Also my_filE, my_file, and my_FILE are three different files.

Your user login name and password are also case sensitive. (This goes with the tradition of UNIX and the "c" programming language being case sensitive.)

Filenames can be up to 256 characters long and can contain letters, numbers, "." (dot), "_" (underscore), "-" (dash), plus some other not recommended characters.

Files with names starting with "." are normally not shown by the ls (list) or dir commands. Think of these files as "hidden". Use ls -a (list with the option "all") to see these files.

"/" is an equivalent to DOS "\" (root directory, meaning the parent of all other directories).

Under Linux, all directories appear under a single directory tree (there are no DOS-style drive letters).

In a configuration file, a line starting with # is a comment.

Below are the links for

Linux essential shortcuts and sanity commands

Common Linux commands for system info

Basic operations

File (de)compression

Process control

Basic administration commands

Package/Software installation

Accessing drives/partitions

Network administration tools

VI editor tips and tricks.

noreply@blogger.com (Vivek H Nayee) — Sat, 25 Apr 2015 11:48:00 +0530

Few tips & tricks on using VI editor.

Operation Modes:

While working with vi editor you would come across following two modes:

Command mode: This mode enables you to perform administrative tasks such as saving files, executing commands, moving the cursor, cutting (yanking) and pasting lines or words, and finding and replacing. In this mode, whatever you type is interpreted as a command.

Insert mode: This mode enables you to insert text into the file. Everything that's typed in this mode is interpreted as input and finally it is put in the file

IMPORTANT:

Here are the key points to your success with vi:

You must be in command mode to use commands. (Press Esc twice at any time to ensure that you are in command mode.)

You must be careful to use the proper case (capitalization) for all commands.

You must be in insert mode to enter text.

Refer to shortcuts and commands.

Vivek H Nayee.