From da4a29c615fac6baa401c3aa1aea49c681dbd260 Mon Sep 17 00:00:00 2001
From: Michele Cereda <cereda.michele@gmail.com>
Date: Tue, 27 Sep 2022 23:32:35 +0200
Subject: [PATCH] Added howto to mount files as virtual file systems

---
 .../mount files as virtual file systems.md    |  3 ++-
 knowledge base/raspberry pi os.md             | 21 ++++++++++++++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/knowledge base/mount files as virtual file systems.md b/knowledge base/mount files as virtual file systems.md
index 2639e8f..4b54433 100644
--- a/knowledge base/mount files as virtual file systems.md	
+++ b/knowledge base/mount files as virtual file systems.md	
@@ -14,7 +14,8 @@ mkfs.ext4 'path/to/file'
 mkdir 'mount/point'
 
 # Mount the file system.
-sudo mount -t 'ext4' 'path/to/file' 'mount/point'
+# The 'loop' option is optional.
+sudo mount -t 'ext4' -o 'loop' 'path/to/file' 'mount/point'
 ```
 
 Prefer `truncate` to `dd` to let the file expand dynamically and be resized (both larger or smaller) without damaging data with `losetup` and `resize2fs`.
diff --git a/knowledge base/raspberry pi os.md b/knowledge base/raspberry pi os.md
index 2de5c70..2f4a6c6 100644
--- a/knowledge base/raspberry pi os.md	
+++ b/knowledge base/raspberry pi os.md	
@@ -1,6 +1,25 @@
 # Raspberry Pi OS
 
-## Let it run containers
+1. [Store files on the SD even when the overlay file system is active](#store-files-on-the-sd-even-when-the-overlay-file-system-is-active)
+2. [Make it able to run containers](#make-it-able-to-run-containers)
+   1. [Kernel containerization features](#kernel-containerization-features)
+   2. [Firewall settings](#firewall-settings)
+3. [Sources](#sources)
+
+## Store files on the SD even when the overlay file system is active
+
+The files just need to be stored on a different file system from `/`. You can partition the SD and use that, or create a file and mount it as a virtual file system:
+
+```sh
+truncate -s '6G' 'file'
+mkfs.ext4 'file'
+mkdir 'mount/point'
+sudo mount -t 'ext4' -o 'loop' 'file' 'mount/point'
+sudo chown 'user':'group' 'mount/point'
+touch 'mount/point/new-file'
+```
+
+## Make it able to run containers
 
 ### Kernel containerization features