Reference only. No concepts explained here — for the why behind any command, see 01 Theory, 02 Terraform, or the 03/04 Lab pages.

POSTGRESHELP LABS · REFERENCE

Command reference — every command used, by tool

Every command run across topics 01–12, with what each flag actually does. Read cmd = command, colored flag = option/argument, right column = plain-English meaning.

Git

Command	Flag	Meaning
git init	—	Turns the current folder into a Git repository (creates `.git/`).
git config user.name "..."	--global	Sets the author name for commits. `--global` applies it to every repo on this machine, not just this one.
git config user.email "..."	--global	Sets the author email for commits — shows up in `git log` and GitHub.
git config --list	—	Prints all active config values, so you can confirm name/email were actually set.
git remote add origin <url>	—	Links this local repo to a remote (GitHub) named `origin` — the default name, not a keyword.
git add .	.	Stages every changed/new file in the current folder for the next commit. `.` means "here and below."
git status	—	Shows what's staged, what's changed but unstaged, and what's untracked — your pre-commit sanity check.
git commit	-m "msg"	`-m` = message. Passes the commit message inline as a string, instead of opening your default editor to type one.
git branch	-M master	`-M` = move/rename (force). Renames the current branch to `master`, overwriting if that name exists.
git push	-u origin master	`-u` = set upstream. Pushes to `origin`'s `master` branch and remembers that pairing, so future `git push`/`pull` need no arguments.
git pull	—	Fetches remote commits and merges them into your current branch, in one step.
ssh-keygen	-t ed25519 -C "email"	`-t` = key type/algorithm. `-C` = comment, usually your email, to label the key on GitHub.
ssh [email protected]	-T	`-T` = disable pseudo-terminal. Tests SSH auth against GitHub without opening a shell.

Terraform

Command	Flag	Meaning
terraform init	—	Downloads the providers your config needs and sets up the local backend. Run once per new/changed config.
terraform validate	—	Checks your `.tf` files are syntactically correct and internally consistent. Fully offline.
terraform fmt	—	Auto-rewrites your files into Terraform's canonical formatting.
terraform plan	—	Shows exactly what would change if you applied — a dry run. Always read this before `apply`.
terraform apply	—	Actually creates/updates real AWS resources to match your config. Prompts for a typed `yes`.
terraform import	<addr> <id>	Maps a real AWS resource onto a resource block already in your config — writes state only.
terraform -version	—	Prints the installed Terraform version and resolved provider versions.

AWS CLI

Command	Flag	Meaning
aws --version	—	Confirms the CLI is installed and on PATH.
aws configure	—	Interactively writes your access key, secret key, default region, and output format to `~/.aws/`.
aws sts get-caller-identity	—	Returns the IAM identity your current credentials resolve to.
aws ec2 describe-vpcs	--vpc-ids <id>	Looks up details for one specific VPC by ID.

Ansible

Command	Flag	Meaning
ansible --version	—	Shows the installed Ansible core version and the Python interpreter.
ansible-galaxy collection install	community.postgresql	Downloads a collection — extra modules not in Ansible core.
ansible-galaxy collection list	—	Lists every collection currently installed.
ansible-playbook <file>.yml	--syntax-check	Parses the playbook's syntax without connecting to any host.
ansible-playbook <file>.yml	—	Actually runs the playbook against the hosts in your inventory.

Liquibase

Command	Flag	Meaning
liquibase --version	—	Confirms Liquibase is installed and on PATH.
liquibase validate	—	Checks the changelog file(s) are well-formed — no DB connection changes made.
liquibase status	—	Connects to the target DB and lists which changesets haven't been applied yet.
liquibase update	—	Applies every pending changeset, in order, and records each in `DATABASECHANGELOG`.

PostgreSQL / psql

Command	Flag	Meaning
psql --version	—	Confirms the PostgreSQL client is installed.
psql	-h <host> -U <user> -d <db>	`-h` host, `-U` user, `-d` database.
java -version	—	Confirms the JDK is installed — a hard dependency for Liquibase.

System / Linux (install & file handling)

Command	Flag	Meaning
sudo dnf install -y <pkg>	-y	Auto-confirm install via the Amazon Linux/RHEL/Fedora package manager.
wget <url>	—	Downloads a file from a URL into the current directory.
tar	-xzf <file> -C <dir>	`-x` extract, `-z` gzip, `-f` file, `-C` target directory.
ln -s <target> <link>	-s	Creates a symbolic shortcut pointing at the target.
curl	-L -o <file> <url>	`-L` follows redirects, `-o` saves to a named file.
find <dir>	-maxdepth 2 -name <pat>	Limits search depth; matches a filename pattern.
mkdir	-p <dir>	Creates the folder (and missing parents) without erroring if it exists.
code	--install-extension <id>	Installs a VS Code extension from the command line.

PowerShell — audit what's installed / configured (Windows)

Command	Flag	Meaning
Get-Command terraform	—	Confirms `terraform.exe` is on PATH. Errors if not installed.
Get-Command git	—	Same PATH check, for Git.
git config user.name	--global	Prints just the configured commit author name.
git config user.email	--global	Prints just the configured commit author email.
git config --list	--global --show-origin	`--show-origin` adds which config file each setting came from.
Get-Command aws	—	Confirms the AWS CLI is on PATH.
aws configure list	—	Shows which profile is active and where each credential value is read from.
Get-Command psql	-ErrorAction SilentlyContinue	Checks if `psql` is on PATH without printing an error if missing.
Get-Service -Name postgresql*	—	Lists any locally installed PostgreSQL Windows service. Empty = no local server.
Get-ItemProperty	HKLM:\...\Uninstall\* \| where DisplayName -like "PostgreSQL"	Registry check — catches an MSI-installed PostgreSQL even with a stopped service.
Test-NetConnection	-ComputerName localhost -Port 5432	Checks if anything is listening on Postgres's default port.
$env:Path -split ';'	—	Prints every folder on PATH — pipe to `Select-String terraform` to isolate one tool.
whoami	—	The current Windows user — distinct from the Git author or AWS IAM identity.

Appendix — other commands worth learning

Not used in this project yet, but commonly needed the moment things go wrong or the project grows.

Git

git log --oneline — compact commit history
git diff — see unstaged changes
git stash — shelve changes temporarily
git rebase -i — rewrite/squash commit history
git revert <hash> — undo a commit safely

Terraform

terraform destroy — tear down everything managed
terraform state list — list tracked resources
terraform state show <addr> — inspect one resource's state
terraform taint <addr> — force recreation on next apply
terraform workspace new <name> — isolate state per environment

Ansible

ansible all -m ping — ad-hoc connectivity check
ansible-playbook --check — dry run, no changes made
ansible-vault encrypt <file> — encrypt secrets at rest
ansible-inventory --list — dump the resolved inventory

Liquibase

liquibase rollback <tag> — revert to a tagged point
liquibase rollbackCount <n> — undo the last N changesets
liquibase diff — compare two databases' schemas
liquibase generateChangeLog — reverse-engineer a changelog

AWS CLI

aws s3 ls — list buckets/objects
aws iam list-users — list IAM users
aws rds describe-db-clusters — inspect Aurora clusters
aws logs tail <log-group> --follow — stream CloudWatch logs

psql & Linux ops

\l \ \dt \ \du — list DBs / tables / roles
EXPLAIN ANALYZE <query> — see the real query plan
pg_dump / pg_restore — backup and restore
systemctl status <service> — check a service's state
journalctl -u <service> -f — tail a service's logs

PowerShell / Windows

winget list — every winget-installed package + version
Get-Package — broader installed-software inventory
Get-NetTCPConnection -LocalPort 5432 — what's bound to that port
Get-Service | Where-Object Status -eq 'Running' — all running services
$env:JAVA_HOME / $env:AWS_PROFILE — check an env var's value