"Out of space" error trying to delete an empty pool

TrueNAS General
1

This is my very first foray into TrueNAS and ZFS, so forgive me if I sound really stupid.

I installed TrueNAS SCALE 25.04.1 onto a new Beelink ME mini PC with a 64GB eMMC for the OS and a pair of 4TB NVMe SSDs for data last week, and have been playing around with it for a few days in a mirror configuration. Then a third 4TB stick arrived in the mail, and I decided to switch to a RAIDZ1 configuration instead. Since I haven’t actually migrated any data to the device, I would like to delete the existing pool and start over.

However, when I deleted my toy datasets from the pool and then tried to remove the pool, I got the following error message: “[EZFS_NOSPC] cannot remove /dev/disk/by-partuuid/(ID deleted): out of space”. Upon closer inspection, the root dataset on the device appears to be hosting about 32MB of system data. This could be the reason I can’t delete the pool anymore, but I can’t seem to find a way to get around it. Googling uncovered advices to turn off snapshot, replication, tasks, apps, instances, etc., but this is clearly not the right advice since I haven’t tried to run any of those on this server yet.

How can I revert this system to just the OS volume plus three free SSDs, short of reinstalling from scratch?

2

Set the system dataset back to the boot pool, perhaps?

1 Like
3

I checked System->Boot, and the boot pool appears to be already on the eMMC drive. Nevertheless, when I go back to the Datasets screen, the sole dataset remaining, which is associated with the disk I’m trying to reclaim, has a mark under “Roles” that says it is being used as the “System Dataset.” I cannot find any way to move the System Dataset in the manuals for 25.04. (I do see a relevant page for 13.0, but the screen being referenced does not seem to exist in 25.04.)

4

TrueNAS GUI, go System, Advanced, Storage, hit Configure button. It brings up window. You select a different pool and the system moves it.

image
image494×284 2 KB

1 Like
5

Thank you! This did the trick. I don’t know how the system dataset got moved to the data pool–I wouldn’t put it past myself to have done it without understanding what I was doing–but in any case, this was what I was looking for. I’ve managed to delete the old pool, set up a new pool, and am now starting to populate a share volume.

6

It’s moved there automatically when you create your first data pool.