docker-composer wordpress asks installation whenever I reboot - wordpress

Question

Everything is fine until I reboot my Ubuntu host.
After reboot, the WordPress page shows the fresh installation page.
There are volumes properly mounted on the host's local directory.
I only have set docker.service to restart the Docker service when reboot.
There must be some mistake I am not aware of.
At least, what shall I do if this thing happens again?
I see all the files mounted on my host shows the latest modification time,
so it looks like the data is persistent...
(edited)
I also tried the external voume as #bilal said in the comment, but it didn't make any difference.
So, now I am thinking this may be related to the process while booting up. like, instead of stop&start, it somehow down/up. But I may be wrong.
version: '3.8'
services:
db:
container_name: $DB_CONTAINER
image: mariadb:latest
restart: always
volumes:
- wordpress_db_data:/var/lib/mysql:rw
environment:
MYSQL_RANDOM_ROOT_PASSWORD: 1
MYSQL_DATABASE: $DB_NAME
MYSQL_USER: $DB_USER
MYSQL_PASSWORD: $DB_PASSWORD
wp:
container_name: $WP_CONTAINER
image: wordpress:latest
depends_on:
- db
- cp
restart: always
volumes:
- wordpress_wp_data:/var/www/html:rw
environment:
WORDPRESS_DB_HOST: $DB_CONTAINER
WORDPRESS_DB_NAME: $DB_NAME
WORDPRESS_DB_USER: $DB_USER
WORDPRESS_DB_PASSWORD: $DB_PASSWORD
WORDPRESS_TABLE_PREFIX: $WP_TABLE_PREFIX
VIRTUAL_HOST: $VIRTUAL_HOST
VIRTUAL_PORT: $VIRTUAL_PORT
LETSENCRYPT_HOST: $VIRTUAL_HOST
LETSENCRYPT_EMAIL: $LETSENCRYPT_EMAIL
#LETSENCRYPT_TEST: 'true'
cp:
build: composer
container_name: ${COMPOSER_CONTAINER}
volumes:
- wordpress_wp_data:/app/wp-content:rw
command: composer install
networks:
default:
external:
name: nginx_proxy
volumes:
wordpress_wp_data:
name: wordpress_wp_data
wordpress_db_data:
name: wordpress_db_data
Here's my volume list
> docker volume ls
DRIVER VOLUME NAME
local wordpress_db_data
local wordpress_wp_data
Here's my docker.service
[Unit]
Description=Docker Application Container Engine
Documentation=https://docs.docker.com
After=network-online.target firewalld.service containerd.service
Wants=network-online.target
Requires=docker.socket containerd.service
[Service]
Type=notify
# the default is not to use systemd for cgroups because the delegate issues still
# exists and systemd currently does not support the cgroup feature set required
# for containers run by docker
ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
ExecReload=/bin/kill -s HUP $MAINPID
TimeoutSec=0
RestartSec=2
Restart=always
# Note that StartLimit* options were moved from "Service" to "Unit" in systemd 229.
# Both the old, and new location are accepted by systemd 229 and up, so using the old location
# to make them work for either version of systemd.
StartLimitBurst=3
# Note that StartLimitInterval was renamed to StartLimitIntervalSec in systemd 230.
# Both the old, and new name are accepted by systemd 230 and up, so using the old name to make
# this option work for either version of systemd.
StartLimitInterval=60s
# Having non-zero Limit*s causes performance problems due to accounting overhead
# in the kernel. We recommend using cgroups to do container-local accounting.
LimitNOFILE=infinity
LimitNPROC=infinity
LimitCORE=infinity
# Comment TasksMax if your systemd version does not support it.
# Only systemd 226 and above support this option.
TasksMax=infinity
# set delegate yes so that systemd does not reset the cgroups of docker containers
Delegate=yes
# kill only the docker process, not all processes in the cgroup
KillMode=process
OOMScoreAdjust=-500
[Install]
WantedBy=multi-user.target

Answer 1

you should use docker volumes for persistent storage what I understand is you mounted dir. See docker volumes for more information.
so your volume section should look like this.
volumes:
- ./wp_data:/var/www/html:rw
- wp_data:/wp_data{volume you want to persist}