i am not an experienced linux user, i only got this from reading other pages. this also worked for me. mabe you can use this at first if you dont have to do something complicated and just want an extra disk to expand the wifi pineapple memory
1. i make sure that the usb is in the correct format that can be read by the wifi pineapple. the FAT32 and the EXT3 /4 should be cleared at first.which one is suited for markIV
2. i then plug in the usb flash drive (or my wifi dongle with micro SD, both worked well with this procedure). the i type "lsusb" in the advance tab in wifi pineapple . it is like list all the recognized usb device i think. it should show 2 entries, one of which is your usb device.sometimes you have to wait 3 mins for it to be recognized. also, the usb LED light should be steady
3. then i type "mkswap /dev/sda" sometimes it is "mkswap/dev/sda1"
4. then i go to the USB tab in the wifi pineapple, the usb device should show with the available memory. example, if you plug in an 8gig stick, it should show up in that tab
5. then i put the "mkswap/dev/sda" command in the cron tab. i dont know, maybe to make sure that it does that during start up.
I did not mess with any settings at first, and everytime i do, i always keep a back up of the "before" settings and the "after" settings
sorry for the noob explanation. so far it works and i have 8 gig of storage in my wifi mark IV