Quick HOWTO: Reduce SWAP Partition Online without reboot in Linux

Recently I had a request to reduce the swap space and allocate that space to some other LV in one of our server.  Below is what I followed and it perfectly worked for me.  :)

Make sure you have enough physical memory to hold the swap contents. 

Now, turn the swap off:

# sync

# swapoff <YOUR_SWAP_PARTITION>

Now check the status

# swapon -s 

Then, Use fdisk command:

# fdisk <YOUR_HARDDISK_Where_SWAP_Resides>

List partitions with "p" commandFind Delete your partition with "d" commandCreate a smaller Linux-Swap partition with "n" commandMake sure it is a Linux-Swap partition (type 82) (Change with "t" command)Write partition table with "w" command

Run "partprobe" to update Filesystem table to kernel. (It is very important before proceeding further)

Then,

mkswap <YOUR_NEW_SWAP_PARTITION>

swapon <YOUR_NEW_SWAP_PARTITION> 

check to make sure swap is turned on

swapon -s 

Now you can use your free space to increase space for other Logical volumes (LV). 

Use fdisk command to create new partition, then 

# partprobe

# pvcreate <NEW_PARTITION_YOU_CREATED>

# vgextend <VG_TO_INCREASE> <YOUR_NEW_PV>

# lvextend -L  +SIZE_TO_INCREASE <LV_NAME> 

Note: It is extreme importance of syncing and turning the swap off before you change any partitions. If you FORGET TO DO THIS, YOU WILL LOST_DATA!!