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====== Ubuntu - Swap - Reduce Swap on an LVM2 Logical Volume ======

Sometimes it can be prudent to reduce swap space after installation.

For example, say you downgraded the amount of RAM in your system from 1 GB to 512 MB, but there is 2 GB of swap space still assigned.

  * It might be advantageous to reduce the amount of swap space to 1 GB, since the larger 2 GB could be wasting disk space.

You have three options: 

  - remove an entire LVM2 logical volume used for swap, or
  - remove a swap file, or
  - reduce swap space on an existing LVM2 logical volume. 

----

===== Determine the name of the swap logical volume =====

<code bash>
lvs
</code>

returns:

<code bash>
  LV       VG   Attr       LSize  Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  backup   vg01 -wi-ao----  3.72g                                                    
  home     vg01 -wi-ao---- 11.86g                                                    
  opt      vg01 -wi-ao----  1.86g                                                    
  root     vg01 -wi-ao----  3.86g                                                    
  sharewiz vg01 -wi-ao----  9.86g                                                    
  srv      vg01 -wi-ao---- 90.86g                                                    
  swap     vg01 -wi-ao----  4.00g                                                    
  usr      vg01 -wi-ao----  3.86g                                                    
  var      vg01 -wi-ao----  6.86g   
</code>

----

===== Reduce an LVM2 swap logical volume =====

Disable swapping for the associated logical volume: 

<code bash>
swapoff -v /dev/mapper/vg01-swap
</code>

----

Reduce the LVM2 logical volume by 512 MB: 

<code bash>
lvm lvreduce /dev/mapper/vg01-swap -L -512M
</code>

----

===== Format the new swap space =====

<code bash>
mkswap /dev/mapper/vg01-swap
</code>

----

===== Enable the extended logical volume =====

<code bash>
swapon -va
</code>

----

===== Test that the logical volume has been reduced properly =====

<code bash>
cat /proc/swaps # free
</code>

returns:

<code bash>
Filename				Type		Size	Used	Priority
/dev/dm-1                               partition	4198396	0	-1
</code>

----

===== Show your free swap space =====

<code bash>
free -tm | grep -i swap
</code>

returns:

<code bash>
Swap:          4099           0        4099
</code>