Created new blog for docker commands

site/posts/neat-docker-commands.md

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+---
+title: "Neat Docker commands"
+excerpt: "Docker does the do."
+date: "2022-01-22"
+---
+
+With the docker command below, you're able to create an Ubuntu shell with the files contained in the current working directory. This is neat for quickly testing out something like a shell script on a different version of Ubuntu, or just seeing if your C program compiles at all somewhere else.
+
+```
+docker run -it -v "$PWD:/workspace" -w /workspace ubuntu:20.04 /bin/bash
+```
+
+Another neat command gives you a `psql` shell in a postgres container. For example, if we were to have the `docker-compose.yml` file below,
+
+```yml
+version: "3.7"
+
+services:
+  postgres:
+    container_name: a-postgres-container
+
+    image: postgres:latest
+
+    environment:
+      POSTGRES_DB: ${POSTGRES_DB}
+      POSTGRES_USER: ${POSTGRES_USER}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
+
+    ports:
+      - "5432:5432"
+```
+
+Then we'd be able to execute what's below to be able to get that `psql` shell, as the user `postgres`.
+
+```
+docker exec -it a-postgres-container psql -U postgres
+```
+
+Not all containers support this, but sometimes you're able to create a bash shell within a container with the following, where `a-container` is the name of the container.
+
+```
+docker exec -it a-container /bin/bash
+```