Converting one file system to another (ext2,ext3,ext4,xfs ) without formatting or removing data in CentOs and RHEL.

Once we opt for a filesystem, it cannot be changed easily – especially if we already have files on it.  
But it is possible to do so using the tool Fstransform.

Fstransform only supports the common filesystems on Linux: ext2, ext3, ext4, ReiserFS, JFS, and XFS. The Windows filesystems NTFS, MS-DOS, and FAT32 are explicitly excluded.

For Fstransform to convert the filesystem, the partition must have at least five percent free space. The more free space available, the more smoothly the conversion will work.

For converting an almost full partition to the XFS filesystem. The hard disk should have at least 10 percent free space available .

For installing Fstransform you will need to install EPL repository .

To install EPL repository in CentOS.

1.Login to the server as root user.

2.At the command prompt ,type the following command to update the server.

   yum -y update 

3.To install the EPEL repository ,type the following command.

   yum -y install peel-release

4. To verify that the EPEL repository has been added ,type the following command:
   
   yum repolist

5.A line similar to the following line should appear in the list of repositories:

  " epel Extra Package for Enterprise Linux  6- x86_64 "

Now install Fstransform using below command 

yum install -y fstransform

 convert a particular file system use the below command .

 fstransform /dev/sdb1 ext4