Folder permissions: "Permission denied (os error 13)"

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1

The Basics

  • Nextcloud Server version (e.g., 29.x.x):
    • 31.0.0
  • Operating system and version (e.g., Ubuntu 24.04):
    • `TrueNAS ElectricEel-24.10.2``
  • Web server and version (e.g, Apache 2.4.25):
    • dunno
  • Reverse proxy and version _(e.g. nginx 1.27.2)
    • ???
  • PHP version (e.g, 8.3):
    • 8.3.17
  • Installation method (e.g. AlO, NCP, Bare Metal/Archive, etc.)
    • TrueNAS app
  • Are you using CloudfIare, mod_security, or similar? (Yes / No)
    • No(?)

Summary of the issue you are facing:

Attempting to use a deduping app (Czkawka) to delete dplicate files in NextCloud’s /var/www/html/data/<username>/files folder fails with “Permission denied (os error 13)” error.

Steps to replicate it:

  1. run Czkawka on /storage (mapped to NextCloud’s /var/www/html/data/<username>/files–see comment below)
  2. select duplicate files to be deleted
  3. click the “Delete” button
  4. witness the error message: “Failed to delete file /storage/path/to/file/filename reason Permission denied (os error 13)”

Comments:

The NextCloud /var/www/html/data/<username>/files folder is actually mapped to TrueNAS’ /mnt/NextCloud/data/<username>/files folder, which, in turn, maps to Czkawka’s /storage folder. Thus, in Czkawka, search happens in /storage. As I was saying, search works fine, but deletion does not.

I thus examined who the owner of the /var/www/html/data/<username>/files folder is:

root@nas1[/mnt/NextCloud/data/dad]# ls -latr
total 36
drwxr-xr-x  5 apps     apps     11 Mar  7 16:53 files
drwxrwx---  4 www-data www-data  8 Mar  7 16:59 ..
drwxr-xr-x  2 www-data www-data  2 Mar  7 17:06 cache
drwxr-xr-x  7 www-data www-data  7 Mar  7 19:03 .
drwxr-xr-x  5 www-data www-data  5 Mar  7 19:03 files_trashbin
drwxr-xr-x  3 www-data www-data  4 Mar  7 19:18 files_versions
drwxr-xr-x 32 www-data www-data 32 Mar  8 18:13 uploads

The question is, then, should I run Czkawka as this apps user? Problem is, Czkawka cannot run as apps. What to do?

Refer to TrueNAS forum topic for more details.

2

You have to run it under the same user as the Nextcloud user. It looks like this is the user www-data in your case.

But if you delete something, it will be missing in the Nextcloud database and you will probably have to do a rescan with the occ command.

3

Thanks, I will attempt to run Czkawka as this user see if it even works, and report back.

Edit: just as I suspected, Czkawka does not run as www-data, just as it does not run as apps either: it crashes or it just simply stops!

4

Apologies! I take back what I said about the apps and www-data users: they are actually TrueNAS built-in users, so they do exist!

Regardless, it looks like Czkawka cannot be run as any of these users. Heck, I even attempted to run Czkawka as root, and it still does not run!