TrueNAs: ElectricEel-24.10.0.2
Hello,
I have described my problem with reinstalling apps in a new pool in the German-speaking part of the forum after I had deleted an old pool for apps because it was no longer accessible and was offline.
Maybe the solution is simply to restore the config and/or the debug that was saved before the action.
Here is the English translation from the German forum section: (Please look at the pictures there! Thank you)
Question what is best to do? I am a relative beginner in TrueNas with little Linux experience … 
Translate:
TrueNAs: ElectricEel-24.10.0.2
Hello,
now that my old pool (RAIDZ1 | 3 wide | 3.64 TiB) from nas4free is mounted correctly and the shares are also working, I dared to try the apps (here NextCloud).
And unfortunately it didn’t quite work although it worked on the first day.
I had an additional ssd (120 GB) installed from the start and this was also listed as “Unused Disks” under “Storage”.
So it went on:
New pool created (Pool_Apps) → As stripe with the 120GB ->> So point 1+2 and 8 when creating → Pool_Apps ok!
Selected in the apps → Nextcloud → Setup install Pool → here selection Pool_Apps → Install → Settings when installing → Admin name+password → Host → Redis password → Database password → cronjob (was like this in an example) → Certificates (from TrueNas - selection) → and finally selected the GPU configuration for me because of amd gpu
because not nVidia → install
Displayed as running in apps and opened via the Web UI. Entered user and password and I was in the Nextcloud.
Calendar and contacts installed and after a lot of fiddling got the links to work so that Evolution synchronizes with Nextcloud
synchronized.
Everything was great until then.
Now late yesterday TrueNas started to “scrub” the Pool_1 after 2.5 hours (about 2.30 a.m.) it was done without errors.
Since I mainly use the NAS alone, it is usually not on all the time, so I shut it down.
Then in the evening I wanted to check some things with Nextcloud, but the pool for apps, Pool_Apps, was offline in Storage.
Datasets only shows my data pool Pool_1. In Dasboard, nothing is displayed under Storage.
Nothing is installed under Apps.
Errors that, I can’t remember where they were displayed over all, are always almost like this, sometimes more sometimes less:
middlewared.service_exception.CallError: [EFAULT] Failed to stop docker service: [EFAULT] Failed to umount dataset: Dataset Pool_Apps/ix-apps not found <<
Mounting the ssd by hand probably didn’t work either because everything stayed as it was.
Then I had the idea to delete the pool Pool_Apps. During the action I saw no messages:
Storage → Pool_Apps → Export/Disconnect → In the pop-up window, check all boxes and enter the Pool_Apps →
Action executed.
The Pool_Apps pool was deleted according to the message …
BUT unfortunately not, everything is as it was.
Well, I thought, let’s leave it as it is and create a new app pool.
This only goes so far that I can create the pool Pool_Apps (Pool_Apps does not work because it exists …) and install Nextcloud again in the new pool.
The app or other apps cannot be installed because I cannot select a pool other than the old deleted pool Pool_Apps under Apps because there is a red message at the top left of Configuration in Apps:
Error In Apps Service → Window pops up when touched:
Application(s) have failed to start:
Failed to umount ‘Pool_Apps/ix-apps’: [EFAULT] Failed to umount dataset Dataset Pool_Apps/ix-apps not found
The bell at the top right also shows:
Critical
Failed to configure docker for Applications: Missing “Pool_Apps/ix-apps/docker, Pool_Apps/ix-apps/app_configs, Pool_Apps/ix-apps/truenas_catalog, Pool_Apps/ix-apps/app_mounts” dataset(s) required for starting docker.
Critical
Failed to configure docker for Applications: Missing “Pool_Apps/ix-apps/truenas_catalog, Pool_Apps/ix-apps/app_mounts, Pool_Apps/ix-apps/app_configs, Pool_Apps/ix-apps/docker” dataset(s) required for starting docker.
Critical
Pool Pool_Apps state is OFFLINE: None
==> So installing apps does not work.
What did GNU say and why did this behavior occur?
Does it do any good since no other pool except the data pool (Pool_1) is installed and the unmounted, deleted but visible APP pool (Pool_Apps) is still “visible” to restore the config of the TrueNas? Or even restore the debug? Both were backed up before the action.
But I would need instructions on what to do first and how, step by step … I have no idea about either, especially as I don’t want to kill my data pool.
Or who has a better solution?
Thanks in advance and see also pictures, maybe it helps … 
Pictures in the German thread, please see link at the beginning of this thread! 
