How can I configure SQL Server Docker to create database files in a custom host directory on Linux Mint?

Below is some guidance to resolve your issue and clarify what’s happening.

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1. Understanding the File Path Issue

When you run SQL Server in a Docker container, SQL Server only “sees” the container’s internal filesystem. Your create‐database statement’s FILENAME path must be a path inside the container where SQL Server has proper permissions. In your statement, you’re using a Linux host directory (e.g.,
/home/blank/Documentos/Cursos/SQL MaxiPrograma/Unidad 3 - Construccion Dbs/), which SQL Server in Docker cannot access unless you explicitly mount it into the container.

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2. Using Bind Mounts Correctly

To have your MDF and LDF files created in your desired host directory, you need to bind mount that directory into the container. For example, if you want your database files to reside where SQL Server expects (such as /var/opt/mssql/data), you can start your container like this:

BASHCopied
docker run -e "ACCEPT_EULA=Y" -e "SA_PASSWORD=YourStrong@Passw0rd" \
-p 1433:1433 \
-v "/home/blank/Documentos/Cursos/SQL MaxiPrograma/Unidad 3 - Construccion Dbs/:/var/opt/mssql/data" \
--name sqlserver -d mcr.microsoft.com/mssql/server:2019-latest

This command maps your host folder to /var/opt/mssql/data inside the container. Then, when you create a database, use the container’s path:

SQLCopied
USE MASTER;
GO
CREATE DATABASE MundoPokemon2 ON
(
    NAME = 'MundoPokemon2-data',
    FILENAME = '/var/opt/mssql/data/MundoPokemon2.mdf',
    SIZE = 10MB,
    MAXSIZE = 500MB,
    FILEGROWTH = 10MB
)
LOG ON
(
    NAME = 'MundoPokemon2-log',
    FILENAME = '/var/opt/mssql/data/MundoPokemon2.ldf',
    SIZE = 10MB,
    MAXSIZE = 500MB,
    FILEGROWTH = 10MB
);

This ensures SQL Server writes to a directory it can access, and that directory is your desired host folder via the bind mount.

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3. Permissions and Ownership Inside the Container

Even if you change the host folder permissions or owner to “mssql,” they won’t affect the container unless that directory is mounted. In the container, SQL Server runs as the “mssql” user and expects the target directory to have appropriate permissions. The bind mount above makes sure that the folder /var/opt/mssql/data inside the container is your host folder—but remember to set the proper Linux permissions on your host folder so that Docker can mount it with read/write access. For example:

BASHCopied
sudo chown -R <your-docker-user>:<your-docker-user> "/home/blank/Documentos/Cursos/SQL MaxiPrograma/Unidad 3 - Construccion Dbs/"
sudo chmod -R 770 "/home/blank/Documentos/Cursos/SQL MaxiPrograma/Unidad 3 - Construccion Dbs/"

Depending on your distribution and Docker setup, you might need to tweak these commands.

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4. Why Is /var/opt/mssql/data Empty?

When you see Azure Data Studio indicating that the database files are located at admin:///var/opt/mssql/data, it refers to the SQL Server container’s internal file system. If you are not mounting a host folder to /var/opt/mssql/data, then changes inside the container will not be visible on your host. Once you bind mount the directory, any changes or new files inside the container’s /var/opt/mssql/data will show up in your host folder (and vice versa).

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Summary

• Mount your desired host directory into the container (commonly at /var/opt/mssql/data).
• Use the container’s path (e.g., /var/opt/mssql/data/MundoPokemon2.mdf) in your SQL CREATE DATABASE statement.
• Ensure proper permissions on the host folder so that Docker can mount and SQL Server can write to it.
• The /var/opt/mssql/data path shown in Azure Data Studio is inside the container; without a mount, you won’t see those files on your host.

Following these steps should solve the "Access is denied" error and help you work with database files in your desired directory.