Server was working fine. I even verified Plex was running fine just moment before I initiated the reboot after installing the update to 7.3.3 from 7.3.2. After reboot (to complete the upgrade) I had my network share working but I got the "No Docker containers installed" on the Docker screen. I rebooted again just to see if that would fix it, but it did not.

I used the "Previous Apps" feature to reinstall the Dockers so they are working again aside from the things I installed from outside of the app store (those are listed and I can click "restore" but nothing happens). What I'm wondering is what happened and will it happen again?
Previous syslog shows Unraid creating a brand-new empty /mnt/cache/docker.img (20 GB) during the post-update boot. But why blank?

tower-diagnostics-20261015-2041.zip

On the first boot into 7.3.3, the cache pool mounted normally with both devices and all of its existing data. Then Docker started. It is set to use /mnt/cache/docker.img, and the log shows it found no file at that path, so it created a new, empty 20 GB image. That is why the Docker page was empty. Unraid only creates a new image when the configured file is missing. It never replaces an existing one, and the update itself does not delete or move files on your pools. So the old image was already missing from /mnt/cache before that boot, or it was somewhere else. Unfortunately the diagnostics only have the logs from after the update, so I can't see what happened before the reboot.

To help find out, please open a terminal and post the output of:

ls -la /mnt/cache

find /mnt -maxdepth 4 -name "*.img" -exec ls -la {} \;

If an older docker.img shows up anywhere, please don't delete it yet.

For the containers you didn't install from Apps: "Previous Apps" can't reinstall those. Their settings are still saved on the flash drive, though. Go to Docker > Add Container, open the Template dropdown and select each one under User templates. The fields fill in from your old settings. Check them, then click Apply. Their appdata is still there, so they should pick up where they left off.

Will it happen again? Only if the image file goes missing again. Nothing in the logs points to 7.3.3 causing this, and the second reboot used the new image normally. If it does happen again, please grab diagnostics before you reboot or reinstall anything. That way we have the logs from before it happened.

output of ls -la /mnt/cache

total 16192232
drwxrwxrwx 1 nobody users          58 Oct 15 20:41 ./
drwxr-xr-x 8 root   root          160 Oct 15 20:09 ../
drwxrwxrwx 1 nobody users          32 Sep 13  2025 Photos/
drwxrwxrwx 1 nobody users           6 Feb  4  2026 Videos/
drwxrwxrwx 1 nobody users         126 Oct 15 20:58 appdata/
-rw-r--r-- 1 nobody users 21474836480 Oct 16 08:08 docker.img

output of find /mnt -maxdepth 4 -name "*.img" -exec ls -la {} \;

-rw-r--r-- 1 nobody users 21474836480 Oct 16 08:11 /mnt/cache/docker.img

This looks like the new docker based on the date. Yeah I should have grabbed the diagnostics before I rebooted again. Maybe I'll reboot again now just to make sure I'm past whatever it was.

Thanks. That confirms the old docker.img no longer exists anywhere, so it was deleted, not moved or renamed.

This also explains why Plex was still working right before you rebooted. Docker runs from a loop-mounted image. If that file is deleted while Docker is running, the loop device keeps it open, so everything keeps working until the image is unmounted at the next reboot or Docker restart. So the file was most likely deleted at some point before the update, maybe even days earlier, and you only saw it on the update reboot. The update itself doesn't delete files on your pools.

I can't see what deleted it because the logs from before the update are gone. Unraid itself doesn't do it, and none of your installed plugins delete docker.img. Since the image was at the root of the cache pool, think about whether anything could have removed files there: a cleanup you did from the console or over SMB, a script, or another tool with access to /mnt/cache.

Rebooting again is fine. The new image is in place and the second boot used it normally.

I appreciate the help. It remains a mystery because I cannot think of anything I might have done that would likely have been the culprit. Something out of the ordinary that I recently did was use a python script to scan pull files from my music Share (read only) and analyzes them locally with an algorithm to assess track moods and then apply that metadata to the Plex via a MCP. I ran this from my Windows computer so since I have "access to /mnt/cache" I suppose the Python script does too. I don't see anything in the script that might do that. Maybe it was something a long time ago, I think the uptime was over 2 months before I rebooted.