Hello friends
I know all the command to reduce the lvm
umount /vg0
fsck -f /dev/volumegroup/lvm
resize2fs /dev/volumegroup/lvm
lvreduce /dev/volumegroup/lvm -L 400M

But when i fire the command
umount /dev/volumegroup/lvm
or
umount /vg0
Then i got the following error
root@localhost ~]# umount /dev/volumegroup/lvm
umount: /vg0: device is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))

This is the output of my /etc/fstab file
#
# /etc/fstab
# Created by anaconda on Mon Oct 11 00:04:01 2010
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=8e8d82b4-11e3-4d6d-8f7e-f0898e245329 / ext4 defaults 1 1
UUID=f6edbfd0-9d76-4669-9c66-7bd131a507ce /boot ext4 defaults 1 2
UUID=6a6455e7-0fbb-42d8-b7cc-717e89bcf62f swap swap defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
/dev/volumegroup/lvm /vg0 ext3 defaults 0 0

I think i must remove the following entry from /etc/fstab

/dev/volumegroup/lvm /vg0 ext3 defaults 0 0
Please guide me
Thanks & Regards
Rahul

Your fstab doesn't help, if we don't know what devices the UUIDs are connected to, but I suspect that your installation lives on the LVM, and you can't unmount your root partition while you're using it (for obvious reasons.) No worries; just boot from a livecd. Fedora's rescue cd mode will work just fine.

Try this steps:

1) fuser -vm /vg0


2) check autofs status -> service autofs stop


3) quotaoff /home


4) reboot

How does this help him, exactly? The OP has a process accessing the volume, which is why it couldn't be unmounted. Rebooting may do NOTHING, except restart the process, and waste time.