从字典字典中读取特定键值(Reading specific key values from a dictionary of dictionary)

 Dockerfile每个RUN指令都在不同的层中执行（如RUN文档中所述）。 
 
 您的Dockerfile有三条RUN指令。 问题是MySQL服务器只能在第一个启动。 在其他的，没有MySQL正在运行，这就是为什么你的mysql客户端连接错误。 
 
 要解决这个问题，你有2个解决方案。 
 
 解决方案1：使用单行RUN 
 
RUN /bin/bash -c "/usr/bin/mysqld_safe &" && \
  sleep 5 && \
  mysql -u root -e "CREATE DATABASE mydb" && \
  mysql -u root mydb < /tmp/dump.sql
 
 解决方案2：使用脚本 
 
 创建可执行脚本init_db.sh ： 
 
#!/bin/bash
/usr/bin/mysqld_safe &
sleep 5
mysql -u root -e "CREATE DATABASE mydb"
mysql -u root mydb < /tmp/dump.sql
 
 将这些行添加到Dockerfile ： 
 
ADD init_db.sh /tmp/init_db.sh
RUN /tmp/init_db.sh

Each RUN instruction in a Dockerfile is executed in a different layer (as explained in the documentation of RUN).
 
In your Dockerfile, you have three RUN instructions. The problem is that MySQL server is only started in the first. In the others, no MySQL are running, that is why you get your connection error with mysql client.
 
To solve this problem you have 2 solutions.
 
Solution 1: use a one-line RUN
 
RUN /bin/bash -c "/usr/bin/mysqld_safe --skip-grant-tables &" && \
  sleep 5 && \
  mysql -u root -e "CREATE DATABASE mydb" && \
  mysql -u root mydb < /tmp/dump.sql
 
Solution 2: use a script
 
Create an executable script init_db.sh:
 
#!/bin/bash
/usr/bin/mysqld_safe --skip-grant-tables &
sleep 5
mysql -u root -e "CREATE DATABASE mydb"
mysql -u root mydb < /tmp/dump.sql
 
Add these lines to your Dockerfile:
 
ADD init_db.sh /tmp/init_db.sh
RUN /tmp/init_db.sh