I accidentally wrote to a delete file through the loop device.
OS: Ubuntu 20.04
Here is my scenario:
1 - I created a RAW image file:
# qemu-img create -f raw sda.img 10G
2 - I created partiton with sfdisk dump:
# sfdisk sda.img < sda.dump
3 - I mounted the image through loop device (loop18):
# losetup -f --show -P sda.img
I get this:
# lsblk /dev/loop18
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
loop18 7:18 0 10G 0 loop
└─loop18p1 259:0 0 9,8G 0 part
4 - I deleted the image file (accidentally):
# rm sda.img
5 - I copied the backup image to the partition:
# dd if=sda1.img.bak of=/dev/loop18p1 status=progress
There was no error. The dd command worked fine.
The losetup command indicates the image file is deleted:
# losetup /dev/loop18
/dev/loop18: [2049]:1972579 ( (deleted))
I wrote randomly data to the partition for test (ctrl+C):
# dd if=/dev/urandom of=/dev/loop18p1 status=progress
146953728 octets (147 MB, 140 MiB) copiés, 4 s, 36,7 MB/s^C
327621+0 enregistrements lus
327621+0 enregistrements écrits
167741952 octets (168 MB, 160 MiB) copiés, 5,10425 s, 32,9 MB/s
Why did it work ? Is it safe for my ext4 file system of my Ubuntu OS ?
Thanks.
