UNOFFICIAL GUIDE: RUN SWAP OVER USB DRIVE IN PFSENSE

JonathanLee

I have an issue after reboot

It shows both now with the swapinfo command

Shell Output - swapinfo -kh
Device              Size     Used    Avail Capacity
/dev/gpt/swapUSB.eli     8.0G       0B     8.0G     0%
/dev/label/swap0     6.6G       0B     6.6G     0%
Total                15G       0B      15G     0%

It should only show /dev/gpt/swapUSB.eli for external swap because that is the only entry in the fstab file. However, both are being listed. the swap0 I only want for dump use coredumps because it is onboard ssd with the pfsense software swap would kill the drive faster. This was my issue before I couldn’t do coredumps on swapUSB because dump can’t use .eli so I wanted to separate swap from the coredumps location. For external usb based swap I want to use .eli to protect it from memory leaks so no one walks off with the drive with everything on it. I do not want to overload the onboard stuff because it is an SSD with pfsense.

dump on is correct thank you this does not use .eli it works does core dumps to that location. Weird that swapinfo shows both now that the labels are added. When is this checked what else loads the info into swap ?

DiagnosticsCommand Prompt
Shell Output - dumpon -l
label/swap0

jimp

The boot script should only be using swap entries listed in /etc/fstab/ so make sure swap0 isn't in fstab at all. The rc.dumpon script doesn't need an entry in fstab so long as the label exists.

JonathanLee

@jimp
I only have one entry in fstab what is weird after a reboot if I do swapinfo it shows both now.. I tested it did a crash and I do get coredumps now on the right drive and that is amazing !! If fstab lists one swap why is it now adding the swap0 to it and not just the swapUSB?

(Swapinfo showing 2 different swaps)

(What is listed in fstab)

Eli is loading also with the correct partition and encrypting on logs

JonathanLee

mer

@JonathanLee FreeBSD has this idea of "device withering".
If your swap partition is NOT mounted/in use, you will likely see a "/dev/da0p2" AND a "/dev/gpt/whateverlabelyougaveit".
Then the first exclusive reference (think mount) makes everything else disappear.
if you do "swapon /dev/da0p2" the /dev/gpt disappears.
If you do "swapon /dev/gpt/whatever" the /dev/da0p2 will likely disappear (not always since this is basically raw device)
Your swapinfo showing both /dev/gpt/swapUSB.eli and /dev/label/swap0 indicate to me they are on 2 different physical devices.
If they are not different physical devices, you have something very odd going on.

JonathanLee

Yes swapusb is a usb and the other is the SSD on the device itself. Two different devices, also .Eli is in use so dump can not use that device only swap can

JonathanLee

@mer I wonder if I do a cron job on it and swapon set it to be specific for usb if it would work, I opened a redmine as the current rc.dumpon does not include a if Eli and or if usb for situations like this. It was not closed right away so it could be fixed with a simple if else situation on the code.

JonathanLee

Fix is to set swapoff on the other drive with a cron job no code is adapted. I am going to update my unofficial guide

mer

@JonathanLee Keep in mind "swapoff" may not immediately free up swap space. I think items in swap need to wind up getting released (basically the VM system recognizes no longer needed) before the swap device is actually taken offline.

castleapp

The unofficial guide for running swap over a USB drive in pfSense explains how to configure a USB drive as swap space. While it can help with memory shortages, it risks reduced performance and potential wear on the USB drive due to frequent read/write cycles. Use cautiously and consider alternatives like increasing RAM.

JonathanLee

@castleapp your right. Again with how affordable usb sticks are why not have that hypothetical emergency gas tank. If you are worried about usb flash drive damage from overuse why not utilize a usb HDD for added longevity. Some systems can’t add memory as it is embedded. Merry Christmas

stephenw10

Hmm @castleapp's reply reads like chatgpt, i.e. spam incoming....

JonathanLee

@stephenw10 I agree it is a little bit off.

patient0

@stephenw10 I reported it as (possible) spam (category 'other) yesterday.