Docker run command with -v flag puts container in Exited status - mysql

Question

I am trying to map a local directory /home/ubuntu/data to /var/lib/mysql folder in container by using -v flag but container's status becomes Exited (0) 1. However, if I don't use -v flag at all, container is Up but this is not what I want. What could be the reason? I see volume mount line is missing in event logs opposed to working example.
$ docker -v
Docker version 17.09.0-ce, build afdb6d4
Dockerfile
FROM ubuntu:16.04
RUN apt-get update \
&& DEBIAN_FRONTEND=noninteractive apt-get install -y mysql-server \
&& sed -i "s/127.0.0.1/0.0.0.0/g" /etc/mysql/mysql.conf.d/mysqld.cnf \
&& mkdir /var/run/mysqld \
&& chown -R mysql:mysql /var/run/mysqld
VOLUME ["/var/lib/mysql"]
EXPOSE 3306
CMD ["mysqld_safe"]
This is the which doesn't work.
$ docker run -i -t -d -v /home/ubuntu/data:/var/lib/mysql --name mysql_container mysql_image
Event logs.
2017-11-... container create 08b44c094... (image=mysql_image, name=mysql_container)
2017-11-... network connect 62bb211934... (container=08b44c094..., name=bridge, type=bridge)
2017-11-... container start 08b44c094... (image=mysql_image, name=mysql_container)
2017-11-... container die 08b44c094... (exitCode=0, image=mysql_image, name=mysql_container)
2017-11-... network disconnect 62bb211934... (container=08b44c094..., name=bridge, type=bridge)
Container logs.
$ docker logs -t mysql_container
2017-11-... mysqld_safe Logging to syslog.
2017-11-... mysqld_safe Logging to '/var/log/mysql/error.log'.
2017-11-... mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
This works without -v
$ docker run -i -t -d --name mysql_container mysql_image
Event logs.
2017-11-... container create 84993141... (image=mysql_image, name=mysql_container)
2017-11-... network connect 62bb2119... (container=84993141..., name=bridge, type=bridge)
2017-11-... volume mount 8c36b53d33... (container=84993141...7, destination=/var/lib/mysql, driver=local, propagation=, read/write=true)
2017-11-... container start 84993141... (image=mysql_image, name=mysql_container)
Container logs.
$ docker logs -t mysql_container
2017-11-... mysqld_safe Logging to syslog.
2017-11-... mysqld_safe Logging to '/var/log/mysql/error.log'.
2017-11-... mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
2017-11-... mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended

Answer 1

It's a little complicated but interesting case.
So how you can check what's happening? Use following command:
docker run -i -t -v /tmp/data:/var/lib/mysql mysql_image bash
Now you are inside container so let's try command:
mysqld_safe
And it's ending but let's look into /var/log/mysql/error.log
We see there:
2017-11-25T17:22:24.006180Z 0 [ERROR] InnoDB: Operating system error number 13 in a file operation.
2017-11-25T17:22:24.006211Z 0 [ERROR] InnoDB: The error means mysqld does not have the access rights to the directory.
2017-11-25T17:22:24.006221Z 0 [ERROR] InnoDB: Operating system error number 13 in a file operation.
2017-11-25T17:22:24.006229Z 0 [ERROR] InnoDB: The error means mysqld does not have the access rights to the directory.
2017-11-25T17:22:24.006237Z 0 [ERROR] InnoDB: Cannot open datafile './ibdata1'
Ok let's see how /var/lib/mysql looks without volume mapping:
root#4474b1cd4300:/var/lib/mysql# ls -lah
total 109M
drwx------ 5 mysql mysql 4.0K Nov 25 17:24 .
drwxr-xr-x 1 root root 4.0K Nov 25 17:13 ..
-rw-r----- 1 mysql mysql 56 Nov 25 17:13 auto.cnf
-rw-r--r-- 1 root root 0 Nov 25 17:13 debian-5.7.flag
-rw-r----- 1 mysql mysql 419 Nov 25 17:13 ib_buffer_pool
-rw-r----- 1 mysql mysql 48M Nov 25 17:13 ib_logfile0
-rw-r----- 1 mysql mysql 48M Nov 25 17:13 ib_logfile1
-rw-r----- 1 mysql mysql 12M Nov 25 17:13 ibdata1
drwxr-x--- 2 mysql mysql 4.0K Nov 25 17:13 mysql
drwxr-x--- 2 mysql mysql 4.0K Nov 25 17:13 performance_schema
drwxr-x--- 2 mysql mysql 12K Nov 25 17:13 sys
mysql:mysql is owner of that directory
We have a lot mysql specific files there
Let's see what we've got with volume mapping:
root#fca45ee1e8fb:/var/lib/mysql# ls -lah
total 8.0K
drwxr-xr-x 2 root root 4.0K Nov 25 17:22 .
drwxr-xr-x 1 root root 4.0K Nov 25 17:13 ..
Docker is mapping this directory as root user
Docker is mapping this directory into host so all files disappear because on host machine that directory is empty
How to get this work?
Change your command to:
CMD chown -R mysql:mysql /var/lib/mysql && if [ ! -c /var/lib/mysql/ibdata1 ]; then mysqld --initialize-insecure; fi && mysqld_safe
What's happening there?
chown -R mysql:mysql /var/lib/mysql - get back mysql:mysql owner
if [ ! -c /var/lib/mysql/ibdata1 ]; then mysqld --initialize-insecure; fi - recreate mysql files with root user without pass but only if files not already exists (required for next runs)
mysqld_safe - run mysql