Docker - committed MySQL image not starting (data directory is unusable) - docker

Question

I used docker commit and now the container won't run properly. Should I:
specify a new data folder within the container, so it will get deleted when I delete the container
delete the host folder contents under /var/lib/mysql?
What I did was I started a Docker container:
docker run -p 33069:3306 --name some-mysql -e MYSQL_ROOT_PASSWORD=test -d mysql:8.0.26 mysqld --default-authentication-plugin=mysql_native_password
Configured some stuff like remote root login, inserted some data into it. Then I wanted to back it up and did:
docker commit -p 6b836bfdf062 backup-mysql8
Which went OK:
root#server:/home/user# docker images | grep mysql
backup-mysql8 latest 1effec593a03 45 minutes ago 514MB
Then I stopped and removed the old container. And tried to start a new one from the backup:
docker run -p 33069:3306 --name some-mysql -e MYSQL_ROOT_PASSWORD=test -d mysql:8.0.26 mysqld --default-authentication-plugin=mysql_native_password -d backup-mysql8
After a few seconds, it would just die.
root#server:/var/lib/mysql# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
13b17d3af8f7 mysql:8.0.26 "docker-entrypoint.s…" 21 minutes ago Exited (1) 21 minutes ago some-mysql
I looked at the logs:
docker logs 13b17d3af8f7
And found this:
2021-09-10T15:15:37.074480Z 0 [ERROR] [MY-013236] [Server] The designated data directory /var/lib/mysql/ is unusable. You can remove all files that the server added to it.
I used inspect and saw that this new host is using my host folder /var/lib/mysql, is that what this means?
docker inspect 13b17d3af8f7
The problem is that that folder on my host machine is already being used and I don't think it's used by the previous container.
root#server:/var/lib/mysql# ls -l
total 110652
-rw-r----- 1 mysql mysql 56 feb 13 2020 auto.cnf
-rw------- 1 mysql mysql 1676 feb 13 2020 ca-key.pem
-rw-r--r-- 1 mysql mysql 1112 feb 13 2020 ca.pem
-rw-r--r-- 1 mysql mysql 1112 feb 13 2020 client-cert.pem
-rw------- 1 mysql mysql 1680 feb 13 2020 client-key.pem
-rw-r--r-- 1 mysql mysql 0 iul 28 06:01 debian-5.7.flag
-rw-r----- 1 mysql mysql 291 feb 13 2020 ib_buffer_pool
-rw-r----- 1 mysql mysql 12582912 feb 13 2020 ibdata1
-rw-r----- 1 mysql mysql 50331648 feb 13 2020 ib_logfile0
-rw-r----- 1 mysql mysql 50331648 feb 13 2020 ib_logfile1
drwxr-x--- 2 mysql mysql 4096 feb 13 2020 mysql
drwxr-x--- 2 mysql mysql 4096 feb 13 2020 performance_schema
-rw------- 1 mysql mysql 1680 feb 13 2020 private_key.pem
-rw-r--r-- 1 mysql mysql 452 feb 13 2020 public_key.pem
-rw-r--r-- 1 mysql mysql 1112 feb 13 2020 server-cert.pem
-rw------- 1 mysql mysql 1676 feb 13 2020 server-key.pem
drwxr-x--- 2 mysql mysql 12288 feb 13 2020 sys
What and how to do it?

Answer 1

if you need persistent data stored, you should map /var/lib/mysql to a host folder instead.
e.g.
docker run -p 33069:3306 --name some-mysql -v ./mydata:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=test -d mysql:8.0.26 mysqld --default-authentication-plugin=mysql_native_password
Update:
docker inspect output just represent the section VOLUME ["/var/lib/mysql"] in Dockerfile.