Docker NFS persistent volume, wordpress error 'Unable to connect to the filesystem.'

General
,
1

My issue:
I’m not able to install any wordpress plugins, I get this error Unable to connect to the filesystem. Please confirm your credentials. This seems like a permissions issue, or something to do with the NFS bind. There are no errors.

I’m able to upload media without a problem.

I’m probably just doing something wrong, or I don’t understand how this docker image works. I hope someone can point me in the right direction. Or give me an suggestion on how to run this stack with a persistent volume for wordpress.

My goal:
Running this stack on a docker swarm (raspberry pi’s) with a persistent volume using NFS. So the wordpress container can run on any node in the cluster. Same goes for the mysql container.

Information
Docker-compose.yml

version: '3.2'

services:
   db:
    image: mariadb
    volumes:
      - db_data:/var/lib/mysql
    environment:
       MYSQL_ROOT_PASSWORD: somewordpress
       MYSQL_DATABASE: wordpress
       MYSQL_USER: wordpress
       MYSQL_PASSWORD: wordpress

   wordpress:
    image: wordpress
    depends_on:
       - db
    volumes:
      - wp_content:/var/www/html
    ports:
       - "80:80"
    environment:
       WORDPRESS_DB_HOST: db:3306
       WORDPRESS_DB_USER: wordpress
       WORDPRESS_DB_PASSWORD: wordpress
       WORDPRESS_DB_NAME: wordpress

volumes:
  db_data:
    driver_opts:
      type: "nfs"
      o: "addr=192.168.1.245,nolock,soft,rw"
      device: ":/vol/mysql"
  wp_content:
    driver_opts:
      type: "nfs"
      o: "addr=192.168.1.245,nolock,soft,rw"
      device: ":/vol/wordpress"

nfs-server export file

/vol *(rw,sync,no_subtree_check,insecure,all_squash,anonuid=0,anongid=0)

File permissions in /vol

drwxrwxrwx  4 root     root     4096 Mar 10 14:59 .
drwxr-xr-x 26 root     root     4096 Mar 10 10:00 ..
drwxr-xr-x  5      999      999 4096 Mar 10 15:18 mysql
drwxrwxrwx  5 www-data www-data 4096 Mar 10 15:17 wordpress

File permissions in /vol/wordpress

drwxrwxrwx  5 www-data www-data  4096 Mar 10 15:17 .
drwxrwxrwx  4 root     root      4096 Mar 10 14:59 ..
-rw-r--r--  1 www-data www-data   235 Mar 10 15:26 .htaccess
-rw-r--r--  1 www-data www-data   420 Nov 30  2017 index.php
-rw-r--r--  1 www-data www-data 19935 Jan  1 20:37 license.txt
-rw-r--r--  1 www-data www-data  7425 Jan  9 02:56 readme.html
-rw-r--r--  1 www-data www-data  6919 Jan 12 06:41 wp-activate.php
drwxr-xr-x  9 www-data www-data  4096 Feb 21 22:09 wp-admin
-rw-r--r--  1 www-data www-data   369 Nov 30  2017 wp-blog-header.php
-rw-r--r--  1 www-data www-data  2283 Jan 21 01:34 wp-comments-post.php
-rw-r--r--  1 www-data www-data  3088 Mar 10 15:17 wp-config.php
-rw-r--r--  1 www-data www-data  2808 Mar 10 15:17 wp-config-sample.php
drwxr-xr-x  5 www-data www-data  4096 Mar 10 15:42 wp-content
-rw-r--r--  1 www-data www-data  3847 Jan  9 08:37 wp-cron.php
drwxr-xr-x 19 www-data www-data 12288 Feb 21 22:09 wp-includes
-rw-r--r--  1 www-data www-data  2502 Jan 16 05:29 wp-links-opml.php
-rw-r--r--  1 www-data www-data  3306 Nov 30  2017 wp-load.php
-rw-r--r--  1 www-data www-data 38883 Jan 12 06:41 wp-login.php
-rw-r--r--  1 www-data www-data  8403 Nov 30  2017 wp-mail.php
-rw-r--r--  1 www-data www-data 17947 Jan 30 11:01 wp-settings.php
-rw-r--r--  1 www-data www-data 31085 Jan 16 16:51 wp-signup.php
-rw-r--r--  1 www-data www-data  4764 Nov 30  2017 wp-trackback.php
-rw-r--r--  1 www-data www-data  3068 Aug 17  2018 xmlrpc.php
2

The problem still inside to container, seems you do not have permission to write on.
try to enter in -it on your Wordpress container and try to write a file on the /var/www/html with the user: www-data
If you cannot, this probably depend from nfs who do not permit it.
Ping back me if you still to have problem.

3

Running this command to get inside the container docker exec -it --user www-data 2901c1629537 bash

Then I ran this command www-data@2901c1629537:~/html$ mkdir -p /var/www/html/dockerforum
As you can see the owner of the file is root, but it should be www-data.
Output of ls -la

www-data@2901c1629537:~/html$ ls -la
total 220
drwxrwxrwx  6 www-data www-data  4096 Mar 11 12:27 .
drwxr-xr-x  1 root     root      4096 Mar  5 14:45 ..
-rw-r--r--  1 www-data www-data   235 Mar 10 20:27 .htaccess
drwxr-xr-x  2 root     root      4096 Mar 11 12:27 dockerforum
-rw-r--r--  1 www-data www-data   420 Nov 30  2017 index.php
-rw-r--r--  1 www-data www-data 19935 Jan  1 20:37 license.txt
-rw-r--r--  1 www-data www-data  7425 Jan  9 02:56 readme.html
-rw-r--r--  1 www-data www-data  6919 Jan 12 06:41 wp-activate.php
drwxr-xr-x  9 www-data www-data  4096 Feb 21 22:09 wp-admin
-rw-r--r--  1 www-data www-data   369 Nov 30  2017 wp-blog-header.php
-rw-r--r--  1 www-data www-data  2283 Jan 21 01:34 wp-comments-post.php
-rw-r--r--  1 www-data www-data  2808 Mar 11 12:20 wp-config-sample.php
-rw-r--r--  1 www-data www-data  3088 Mar 11 12:20 wp-config.php
drwxr-xr-x  5 www-data www-data  4096 Mar 11 12:24 wp-content
-rw-r--r--  1 www-data www-data  3847 Jan  9 08:37 wp-cron.php
drwxr-xr-x 19 www-data www-data 12288 Feb 21 22:09 wp-includes
-rw-r--r--  1 www-data www-data  2502 Jan 16 05:29 wp-links-opml.php
-rw-r--r--  1 www-data www-data  3306 Nov 30  2017 wp-load.php
-rw-r--r--  1 www-data www-data 38883 Jan 12 06:41 wp-login.php
-rw-r--r--  1 www-data www-data  8403 Nov 30  2017 wp-mail.php
-rw-r--r--  1 www-data www-data 17947 Jan 30 11:01 wp-settings.php
-rw-r--r--  1 www-data www-data 31085 Jan 16 16:51 wp-signup.php
-rw-r--r--  1 www-data www-data  4764 Nov 30  2017 wp-trackback.php
-rw-r--r--  1 www-data www-data  3068 Aug 17  2018 xmlrpc.php

I think this has to do with the all_squash,anonuid=0,anongid=0 in the nfs export.

4

you understand well.
you should modify export parameters:

(rw,all_squash,anonuid=33,anongid=33)

Have a good day.
Let me know if will works.

5

Yes, thank you that worked. I still had to add the insecure option to the NFS export. I think because docker connect from a really high port.

I also made 2 separate exports, 1 for mysql and 1 for wordpress. The mysql image uses user 999, and the wordpress image uses user 33. Thanks for your help.