Copying Existing Data¶

Titan provides lots of freedom for how you might populate data into a new repository. You might run some scripts to generate data, load data from a database dump, or replicate data into the container. Titan does not try to encode these database-specific mechanisms into the tool, but does provide some platform-agnostic capabilities for loading data. In this section, we show how you can copy data files from an existing database installation, either from a server or on your laptop.

Determining Database Files¶

Every database has some type of persistent data beneath it. For Titan, we rely on the docker image to tell us what data needs to be persisted. You can find out exactly what an image expects by running docker inspect <image> and look for the Volumes section. For example, docker inspect postgres:11 shows:

"Volumes": {
    "/var/lib/postgresql/data": {}
},

Most databases have a single directory for persistent data, but some may have more than one. For example, docker inspect mongo:latest shows:

"Volumes": {
    "/data/configdb": {},
    "/data/db": {}
},

This tells you what data is expected when running the container and (if there are multiple volumes)

Copying Data Into a Repository¶

The titan cp command is designed to copy this data into a running repository. To do this, first start a container running. Then, use the the titan cp command:

titan cp -s /path/to/postgres/data mypostgres

This will take data located on your latop and copy into that repository.

Warning

This command will stop and re-start any repository, which will interrupt any active connections.

:: warning:

The source data must not be changing at the time this command is run, or
else it will not result in a transactionally consistent snapshot. Be sure
to quiesce or shut down any database that may be writing to the source
data files prior to running the command.

Note

If your repository has multiple persistent volumes, you will need to use the -d destination parameter to specify where the data should go, such as titan cp -s /path/to/mongo/db -d /data/db mymongo. You may need to run multiple such commands if you need to migrate