in this example we will use a 4gb usb
3gb for storage an 1 gb for swap

on any linux operation system format your usb to ext4 for both 3gb and 1 gb partition.
then go to wifi pineapple web interface, on usb tab change every thing with the fallowing code lines.

config global automount
       option from_fstab 1
       option anon_mount 1

config global autoswap
       option from_fstab 1
       option anon_swap 1

config mount
       option target   /usb
       option device   /dev/sda1
       option fstype   ext4
       option options  rw,sync
       option enabled  1
       option enabled_fsck 0

config swap
       option device   /dev/sda2
       option enabled  1

then ssh to your pineapple or on the web interface, advance tab execute command part past the fallowing command.

mkswap /dev/sda2

and you will see something like this:

Setting up swapspace version 1, size = 1002032 kB
no label, UUID=97996185-a731-4d1e-92d8-1017fdb3603e

Now reboot your wifi pineapple

for verification run the command free
and your line beginning with swap word should look like this

Swap: 974844 0 974844

or any number else depending on you size chosen but not

Swap: 0 0 0