From 677b1d980ba3445a013fa83c4e3306bcea508da0 Mon Sep 17 00:00:00 2001
From: Pierre HUBERT <pierre.git@communiquons.org>
Date: Sat, 7 Dec 2024 23:09:31 +0100
Subject: [PATCH] Add README

---
 README.md | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index e6a72ac..c12163e 100644
--- a/README.md
+++ b/README.md
@@ -1,13 +1,22 @@
 # Docker migration helper
+This repo contains a `Dockerfile` that can helps you in performing your Docker images migration.
 
-## Test
-Create an outdated database
+This repository will:
+
+* Perform a temporary copy the old database
+* Initialize a new empty database with the default user / password couple provided as environment variables (`POSTGRES_USER` and `POSTGRES_PASSWORD`)
+* Run `pg_upgrade` from the copy of the old database to the new database
+* Replace the old database with the new one
+* Move the copy of the old database as sub-directory of the new database (in `old_db` directory, to allow rollback in case of failure)
+
+## Perform the migration
+Create an outdated database:
 ```bash
 mkdir test-db
 docker run --rm --name testdb -u 1000 -e POSTGRES_PASSWORD=password -v $(pwd)/test-db:/var/lib/postgresql/data -it postgres:16
 ```
 
-Perform the migration:
+Perform the migration (you need to replace `POSTGRES_USER` and `POSTGRES_PASSWORD` with the credentials of the root user of the database):
 ```bash
-./build.sh && docker run -u 1000 -e POSTGRES_USER=postgres -e POSTGRES_PASSWORD=password -v $(pwd)/test-db:/db --rm -it pierre42100/postgresmig:16to17
-```
\ No newline at end of file
+docker run -u 1000 -e POSTGRES_USER=postgres -e POSTGRES_PASSWORD=password -v $(pwd)/test-db:/db --rm -it pierre42100/postgresmig:16to17
+```