SQL Server Docker container immediately exiting

If you use the sudo command to create a folder outside of your home directory structure for use by Docker then that folder is going to be owned by the root user, e.g.:

$ sudo mkdir /var/mssql-data

$ ls -la /var/mssql-data
total 0
drwxr-xr-x   2 root  wheel    64B 26 May 11:31 ./
drwxr-xr-x  30 root  wheel   960B 26 May 11:31 ../

When you try to launch an SQL Server container using a volume mapping with that folder the container will fail to start – because the Docker backend process doesn’t have access – and you will see the "system directory could not be created" error message, e.g.:

$ docker run -e "ACCEPT_EULA=Y" -e "SA_PASSWORD=StrongPassw0rd" -p 1433:1433 -v /var/mssql-data:/var/opt/mssql --name sqlservercontainer -d mcr.microsoft.com/mssql/server:2019-latest
9d6bf76a91af08329ea07fafb67ae68410d5320d9af9db3b1bcc8387821916da

$ docker logs 9d6bf76a91af08329ea07fafb67ae68410d5320d9af9db3b1bcc8387821916da
SQL Server 2019 will run as non-root by default.
This container is running as user mssql.
To learn more visit https://go.microsoft.com/fwlink/?linkid=2099216.
/opt/mssql/bin/sqlservr: Error: The system directory [/.system] could not be created. File: LinuxDirectory.cpp:420 [Status: 0xC0000022 Access Denied errno = 0xD(13) Permission denied]

To correct the situation you need to give your own account access to the folder and then a container using that volume mapping will start successfully:

$ sudo chown $USER /var/mssql-data

$ docker run -e "ACCEPT_EULA=Y" -e "SA_PASSWORD=StrongPassw0rd" -p 1433:1433 -v /var/mssql-data:/var/opt/mssql --name sqlservercontainer -d mcr.microsoft.com/mssql/server:2019-latest
3b6634f234024e07af253e69f23971ab3303b3cb6b7bc286463e196dae4de82e