UNIX for Advanced & Expert Users

Linux !!!

The "default file system" for Linux; in general, is ext2 or ext3.

From above:

Most people would use fdisk or mount to see what filesystems are used on a Linux installation.

yes i know it but those commands shows all the file systems present in system. and i am not able to figure out which is "DEFAULT FILE SYSTEM"

'default file system' barely makes sense. The Linux OS is just one single file, the kernel, which doesn't even need to be in the file tree when the system boots. Often you'll find it in a special partition by itself. If you're asking about the root filesystem, it's the only one mounted on / .

there is default file system funda in Solaris thats why i am curious to know about it more...(which is UFS in solaris usually )

Linux has no default file system. You can compile your own kernel without any support for any filesystem; it will always panic, but still, it's possible. On the other hand I've seen Linux boot off an NTFS partition. It all depends on what you distribution thinks is important. Usually they have support for Ext2/Ext3 and ReiserFS. Some add JFS(2) and XFS to that. But in the end it comes down to which one is the best for the task at hand.