From 29b23bbcbc225bd0a1393b1a86aaac3bb2f8a721 Mon Sep 17 00:00:00 2001
From: Johannes Schauer Marin Rodrigues <josch@mister-muffin.de>
Date: Sun, 22 May 2022 02:57:01 +0200
Subject: [PATCH] document how to build on top of an existing tarball

---
 mmdebstrap | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mmdebstrap b/mmdebstrap
index cd35ddc..d11e0f2 100755
--- a/mmdebstrap
+++ b/mmdebstrap
@@ -6994,6 +6994,17 @@ As a docker/podman replacement:
     root
     $ rm chroot.tar
 
+You can re-use a chroot tarball created with mmdebstrap for further refinement.
+Say you want to create a minimal chroot and a chroot with more packages
+installed, then instead of downloading and installing the essential packages
+twice you can instead build on top of the already present minimal chroot:
+
+    $ mmdebstrap --variant=apt unstable chroot.tar
+    $ mmdebstrap --variant=custom --setup-hook \
+        'mmtarfilter "--path-exclude=/dev/*" < chroot.tar | tar -C "$1" -x' \
+        --customize-hook='chroot "$1" apt-get install --yes pkg1 pkg2' \
+        '' chroot-full.tar
+
 =head1 ENVIRONMENT VARIABLES
 
 =over 8