Resize LV Swap space

Check out current size of volume group - is there enough space to extend the swap?

[root@sbt-centos ~]# vgs
  VG           #PV #LV #SN Attr   VSize  VFree
  vg_sbtcentos   1   3   0 wz--n- 99.51g    0 

 No free space on the VG.  So add another disk to the VG:-

[root@sbt-centos ~]# vgextend vg_sbtcentos /dev/sdb
  No physical volume label read from /dev/sdb
  Physical volume "/dev/sdb" successfully created
  Volume group "vg_sbtcentos" successfully extended


Check space has been added:-

[root@sbt-centos ~]# vgs
  VG           #PV #LV #SN Attr   VSize   VFree 
  vg_sbtcentos   2   3   0 wz--n- 100.50g 1020.00m


Check current swap size:-

[root@sbt-centos ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          1878        523       1354          0         28        184
-/+ buffers/cache:        310       1568
Swap:         4031          0       4031


Turn off the swap device:-

[root@sbt-centos ~]# swapoff -v /dev/vg_sbtcentos/lv_swap
swapoff on /dev/vg_sbtcentos/lv_swap
Resize the LV that the swap lives on:-

[root@sbt-centos ~]# lvresize -L +512M /dev/vg_sbtcentos/lv_swap
  Extending logical volume lv_swap to 4.44 GiB
  Logical volume lv_swap successfully resized

Recreate the swapspace on the extended swap LV (note the UUID has changed, if you use UUID in /etc/fstab you'll have to amend accordingly):-

[root@sbt-centos ~]# mkswap /dev/vg_sbtcentos/lv_swap
mkswap: /dev/vg_sbtcentos/lv_swap: warning: don't erase bootbits sectors
        on whole disk. Use -f to force.
Setting up swapspace version 1, size = 4653052 KiB
no label, UUID=3e5bd2cf-048e-4c8b-a631-a00ef6a5664a



And turn the swap device back on:-

[root@sbt-centos ~]# swapon -va
swapon on /dev/mapper/vg_sbtcentos-lv_swap
swapon: /dev/mapper/vg_sbtcentos-lv_swap: found swap signature: version 1, page-size 4, same byte order
swapon: /dev/mapper/vg_sbtcentos-lv_swap: pagesize=4096, swapsize=4764729344, devsize=4764729344


And finally, show the new swap space:-

[root@sbt-centos ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          1878        523       1354          0         28        184
-/+ buffers/cache:        310       1568
Swap:         4543          0       4543

Alternatively, if there's spare space on an LV it could be reduced and allocated to the swap LV.  See here http://linuxscrapbook.blogspot.co.uk/2014/02/reduce-lv-and-file-system.html