Named Volumes

Assignment

• Database upgrade with containers
• Create a postgres container with named volume psql using version 9.6.4
• Use Docker Hub to learn VOLUME path and versions needed to run it
• Check logs, stop container
• Create a new postgres container with same named volume using 9.6.5
• Check logs to validate
• (this only works with patch versions, most SQL DB's require manual commands to upgrade DB's to major/minor versions, i.e. it's a DB limitation not a container one)

Solution

~> docker container run -d --name psql -v psql:/var/lib/postgresql/data postgres:9.6.4
0b0ee853371be32b8a1bab44f651385cd89c20eb2c759651e0113cb9456e0837

~> docker container ls
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS        NAMES
0b0ee853371b        postgres:9.6.4      "docker-entrypoint..."   7 seconds ago       Up 5 seconds        5432/scp     psql

~> docker container logs -f psql
...
PostgreSQL init process complete; ready for start up.

LOG:  database system was shut down at 2017-10-01 11:04:59 UTC
LOG:  MultiXact member wraparound protections are now enabled
LOG:  database system is ready to accept connections
LOG:  autovacuum launcher started

~> docker container stop psql
psql

~> docker container run -d --name psql2 -v psql:/var/lib/postgresql/data postgres:9.6.5
98c249076a897879f3e87ede39eedc059e0dbd2ab83094677c6fc7d1331bf45e

~> docker container ls -a
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                PORTS               NAMES
98c249076a89        postgres:9.6.5      "docker-entrypoint..."   29 seconds ago      Up 27 seconds        5432/tcp            psql2
0b0ee853371b        postgres:9.6.4      "docker-entrypoint..."   5 minutes ago       Exited (0) About a minute ago            psql

~> docker volume ls
DRIVER              VOLUME NAME
local               psql

~> docker container logs psql2
LOG:  database system was shut down at 2017-10-01 11:09:15 UTC
LOG:  MultiXact member wraparound protections are now enabled
LOG:  database system is ready to accept connections
LOG:  autovacuum launcher started