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:

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

lvs

returns:

  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   

Disable swapping for the associated logical volume:

swapoff -v /dev/mapper/vg01-swap

Reduce the LVM2 logical volume by 512 MB:

lvm lvreduce /dev/mapper/vg01-swap -L -512M

mkswap /dev/mapper/vg01-swap

swapon -va

cat /proc/swaps # free

returns:

Filename				Type		Size	Used	Priority
/dev/dm-1                               partition	4198396	0	-1

free -tm | grep -i swap

returns:

Swap:          4099           0        4099