Mounted LUKS file turns into plaintext directory

I followed the CentOS instructions to create a Linux Encrypted Filesystem with dm-crypt.

This results in what appears to be an encrypted file mounted as a file system, when I checked losetup -l, mount -l and cryptsetup status secretfs, everything looked as would be expected.

losetup -l

mount -l

cryptsetup status secretfs

After restarting the computer, and without issuing any commands to losetup, cryptsetup and mount, the mounted (before restart) encrypted file (secretfs mounted at /mnt/secretfs) has turned into a normal plaintext folder, all files that existed in the mounted encrypted file, are readable at /mnt/secretfs without having to open the encrypted file and mount it.

losetup

cryptsetup

mount

secretfs

/mnt/secretfs

/mnt/secretfs

This was unexpected and appears to make mounting an encrypted file insecure, I would appreciate any guidance to ensure that mounting an encrypted file always requries the passphrase to view it's contents and those contents are not copied to an unencrypted location.

Script

#!/bin/bash

set -e

# encrypted disk
dd of=secretfs bs=20G count=0 seek=8
chmod 600 secretfs
losetup /dev/loop0 secretfs
cryptsetup -y luksFormat /dev/loop0
cryptsetup luksOpen /dev/loop0 secretfs
cryptsetup status secretfs
mke2fs -j -O dir_index /dev/mapper/secretfs
tune2fs -l /dev/mapper/secretfs
mkdir /mnt/secretfs
mount /dev/mapper/secretfs /mnt/secretfs


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