---
tags: 🛠 tools
---

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background-size: cover !important;
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background-attachment: fixed !important;
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h1 {
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justify-content: center;
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# 🐳 Docker

:::info
:information_source: **Disclaimer**

This note is for **`controller`** level so that this note doesn't contain any in-depth information. The purpose of this note is for quick referencing and explain **how to use** the tool in simple language.
:::

:::info
:link: **Further Reading**
- Docker documentation: https://docs.docker.com/
- `@LearnXinYminutes/docker`: https://learnxinyminutes.com/docs/docker/
:::

<hr>

:::success

:information_source: **Conventions**

- `$variable`: In the codeblocks below, the term started with `$` sign is the terms that need to be filled with your values. (*Eg: `$name` would be replaced by `postgres`*)
- `[optional]`: An optional field, it could be replaced or be omitted
- `(term1|term2)`: An option group, you have to chose between values inside the brackets
- `[term1|term2]`: An optional group, you have to chose between values inside the brackets or omit the group.
- The codeblocks have the line number would be **followed step by step**
- The codeblocks don't have line number would be treated as ***an option group***
:::

## Common commands

Docker has 2 types of commands:

docker ($mc|$ac) [--$option [$value]] [$action] $value

Eg:

docker image ls

- **Management commands** (`mc`)
- There are the major commands such as
`builder`, `buildx`, `compose`, `config`, `container`, `context`,
`manifest`, `network`, `node`, `plugin`, `scan`, `secret`, `service`,
`stack`, `swarm`, `system`, `trust`, `volume`
- **Action commands** (`ac`)

## UseCase: How to deploy Postgres Image on Docker

1. We firstly need to fetch the postgres image if the local machine doesn't contain it.
**Note:** Postgres requires the authentication password, so that we have to define it as an environment variable with `-e` option.

    docker run -e -d POSTGRES_PASSWORD=$password postgres

:::spoiler ❓ *What if I don't attach the password into the command?*

    docker run postgres

Result:

    Error: Database is uninitialized and superuser password is not specified.
       You must specify POSTGRES_PASSWORD to a non-empty value for the
       superuser. For example, "-e POSTGRES_PASSWORD=password" on "docker run".

       You may also use "POSTGRES_HOST_AUTH_METHOD=trust" to allow all
       connections without a password. This is *not* recommended.

       See PostgreSQL documentation about "trust":
       https://www.postgresql.org/docs/current/auth-trust.html

:::
2. When the container is runned successfully, we will check it's name with **`docker ps`**
Result:

    CONTAINER ID   IMAGE      COMMAND                  CREATED         STATUS         PORTS      NAMES
    bc9bf443024c   postgres   "docker-entrypoint.s…"   3 minutes ago   Up 3 minutes   5432/tcp   gracious_mccarthy

3. And now we start to run the postgres with container's CLI

    docker exec -it "gracious_mccarthy" bash

- `-i`: ***Interactive***, allows you to interact with the shell
- `-t`: ***TTY***, give the output as a normal terminal

We are in the postgres container bash shell now, let open the postgres CLI `psql` and try some commands.

    root@bc9bf443024c:/# ls
    bin   dev                         etc   lib    media  opt   root  sbin  sys  usr
    boot  docker-entrypoint-initdb.d  home  lib64  mnt    proc  run   srv   tmp  var
    
    root@bc9bf443024c:/# su postgres
    
    postgres@bc9bf443024c:/$ psql
    psql (14.2 (Debian 14.2-1.pgdg110+1))
    Type "help" for help.

    postgres=# \conninfo
    You are connected to database "postgres" as user "postgres" via socket in "/var/run/postgresql" at port "5432".
    postgres=#