Persisting databases with named volumes on Windows with docker compose

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With all things containers I refer to my good friend Andrew Pruski. Known as dbafromthecold on twitter he blogs at https://dbafromthecold.com

I was reading his latest blog post Using docker named volumes to persist databases in SQL Server and decided to give it a try.

His instructions worked perfectly and I thought I would try them using a docker-compose file as I like the ease of spinning up containers with them.

I created a docker-compose file like this which will map my backup folder on my Windows 10 laptop to a directory on the container and two more folders to the system folders on the container in the same way as Andrew has in his blog.

version: '3.7'
services:
    2019-CTP23:
        image: mcr.microsoft.com/mssql/server:2019-CTP2.3-ubuntu
        ports:  
          - "15591:1433"
          - "5022:5022"
        environment:
          SA_PASSWORD: "Password0!"
          ACCEPT_EULA: "Y"
        volumes: 
          - C:MSSQLBACKUPKEEP:/var/opt/mssql/backups
          - C:MSSQLDockerFilesdatafiles:/var/opt/sqlserver
          - C:MSSQLDockerFilessystem:/var/opt/mssql

and then from the directory I ran

docker-compose up -d

This will build the containers as defined in the docker-compose file. The -d runs the container in the background. This was the result.

The command completed successfully but as you can see on the left the container is red because it is not running. (I am using the Docker Explorer extension for Visual Studio C

I inspected the logs from the container using

docker logs ctp23_2019-CTP23_1

which returned

This is an evaluation version. There are [153] days left in the evaluation period.
This program has encountered a fatal error and cannot continue running at Tue Mar 26 19:40:35 20
19
The following diagnostic information is available:
Reason: 0x00000006 Status: 0x40000015 Message: Kernel bug check Address: 0x6b643120
Parameters: 0x10861f680
Stacktrace: 000000006b72d63f 000000006b64317b 000000006b6305ca
000000006b63ee02 000000006b72b83a 000000006b72a29d
000000006b769c02 000000006b881000 000000006b894000
000000006b89c000 0000000000000001
Process: 7 – sqlservr
Thread: 11 (application thread 0x4)
Instance Id: e01b154f-7986-42c6-ae13-c7d34b8b257d
Crash Id: 8cbb1c22-a8d6-4fad-bf8f-01c6aa5389b7
Build stamp: 0e53295d0e1704ae5b221538dd6e2322cd46134e0cc32be49c887ca84cdb8c10
Distribution: Ubuntu 16.04.6 LTS
Processors: 2
Total Memory: 4906205184 bytes
Timestamp: Tue Mar 26 19:40:35 2019
Ubuntu 16.04.6 LTS
Capturing core dump and information to /var/opt/mssql/log…
dmesg: read kernel buffer failed: Operation not permitted
No journal files were found.
No journal files were found.
Attempting to capture a dump with paldumper
WARNING: Capture attempt failure detected
Attempting to capture a filtered dump with paldumper
WARNING: Attempt to capture dump failed. Reference /var/opt/mssql/log/core.sqlservr.7.temp/log/
paldumper-debug.log for details
Attempting to capture a dump with gdb
WARNING: Unable to capture crash dump with GDB. You may need to
allow ptrace debugging, enable the CAP_SYS_PTRACE capability, or
run as root.

which told me that …………. it hadn’t worked. So I removed the containers with

docker-compose down

I thought I would create the volumes ahead of time like Andrew’s blog had mentioned with

docker volume create mssqlsystem
docker volume create mssqluser

and then use the volume names in the docker-compose file mapped to the system folders in the container, this time the result was

ERROR: Named volume “mssqlsystem:/var/opt/sqlserver:rw” is used in service “2019-CTP23” but no declaration was found in the volumes section.

So that didnt work either ??

I decided to inspect the volume definition using

docker volume inspect mssqlsystem

I can see the mountpoint is /var/lib/docker/volumes/mssqlsystem/_data so I decided to try a docker-compose like this

version: '3.7'
services:
    2019-CTP23:
        image: mcr.microsoft.com/mssql/server:2019-CTP2.3-ubuntu
        ports:  
          - "15591:1433"
          - "5022:5022"
        environment:
          SA_PASSWORD: "Password0!"
          ACCEPT_EULA: "Y"
        volumes: 
          - C:MSSQLBACKUPKEEP:/var/opt/mssql/backups
          - /var/lib/docker/volumes/mssqluser/_data:/var/opt/sqlserver
          - /var/lib/docker/volumes/mssqlsystem/_data:/var/opt/mssql

and then ran docker-compose up without the -d flag so that I could see all of the output

You can see in the output that the system database files are being moved. Thatlooks like it is working so I used CTRL + C to stop the container and return the terminal. I then ran docker-compose up -d and

I created a special database for Andrew.

I could then remove the container with

docker-compose down

To make sure there is nothing up my sleeve I altered the docker-compose file to use a different name and port but kept the volume definitions the same.

version: '3.7'
services:
    2019-CTP23-Mk1:
        image: mcr.microsoft.com/mssql/server:2019-CTP2.3-ubuntu
        ports:  
          - "15592:1433"
          - "5022:5022"
        environment:
          SA_PASSWORD: "Password0!"
          ACCEPT_EULA: "Y"
        volumes: 
          - C:MSSQLBACKUPKEEP:/var/opt/mssql/backups
          - /var/lib/docker/volumes/mssqluser/_data:/var/opt/sqlserver
          - /var/lib/docker/volumes/mssqlsystem/_data:/var/opt/mssql

I ran docker-compose up -d again and connected to the new container and lo and behold the container is still there

So after doing this, I have learned that to persist the databases and to use docker-compose files I had to map the volume to the mountpoint of the docker volume.

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