How to Use Swap in Ubuntu ?

You can always create swap file

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by imaginestudio repository

To add more swap space. This is not same (in every aspect) as swap partition but it will be easy and dynamic.

Change /media/fasthdd/swapfile.img to anything you like, for example it can be /swap.img as well. /media/fasthdd/swapfile.img is just example filename, if you are using this one then of course there must be directory /media/fasthdd/ with enough free space for your new swap file.

Use any of terminal applications to run commands. All command should be run with root privileges, to do this you can either add sudo to beginning of every command or run sudo bash before running commands.

1. Create empty file:
This file will contain virtual memory contents so make file big enough for your needs. This one will create 1Gb file which means +1Gb swap space for your system:

dd if=/dev/zero of=/media/fasthdd/swapfile.img bs=1024 count=1M  

If you want to make 3Gb file then change count value to count=3M. See man dd for more information.

2. Bake swap file:
Following command is going to make "swap filesystem" inside your fresh swap file.

mkswap /media/fasthdd/swapfile.img  

3. Bring up on boot:
To make sure that your new swap space is activated while booting up computer you should add it to filesystem configuration file /etc/fstab. Add it to end of file, this is recommended because other filesystems (at least one that contains swap file) must be mounted in read-write mode before we can access any files.

# Add this line to /etc/fstab  /media/fasthdd/swapfile.img swap swap sw 0 0  

4. Activate:
You can either reboot your computer or activate new swap file by hand with following command:

swapon /media/fasthdd/swapfile.img  

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If everything goes well

you should see that more swap space is available for use. You can use following commands to check your new swap and confirm that it is active:

cat /proc/swaps    Filename                           Type       Size    Used    Priority    /media/fasthdd/swapfile.img        file       8388604 2724    -1    grep 'Swap' /proc/meminfo    SwapCached:         4772 kB    SwapTotal:       8388604 kB    SwapFree:        8355812 kB  

How add new/otherJava Versions in linux

 just download the java( tar.gz files) which you want  install in linux

extract that  for example:

I have downloaded the Jdk1.7.tar.gz for 64 bit,placed on the opt/local

follow:

ln -s jdk1.7.0 newjava

then edit the  profile file and add the following linesat bottom

vi /etc/profile

export JAVA_HOME=/opt/local/newjava
export PATH=$PATH:$JAVA_HOME/bin
export CLASSPATH=.:$JAVA_HOME/jre/lib:$JAVA_HOME/lib:$JAVA_HOME/lib/tools.jar

How do I cleanup temp files Ubuntu?

Ubuntu software packaging system can accumulate unused packages or temporary files. These temporary files, also called caches, contain package files from all of the packages that you have ever installed. Eventually, this cache can grow quite large. Removing them allows you to reclaim space on your computer's hard drive for storing your documents, music, photographs, or other files.

To clear the cache you can use either the clean or the auto-clean op for a command-line program called apt-get. The clean command will remove every single cached item, while the auto-clean command only removes cached items that can no longer be downloaded (these items are often unnecessary).

To run clean go to Applications --> Accessories --> Terminal and Type

    $ sudo apt-get clean

and it will ask password and give the password

packages can also become unused over time. If a package was installed to assist with running another program- and that program was subsequently removed-you no longer need the supporting package. You can remove it with autoremove

Terminal and Type

    $ sudo apt-get autoremove

it will remove the unnecessary packages.