# mdconfig command issues



## bsaidus (Sep 23, 2022)

Hello.
I've created a memory disk file named fimage.img size 1GB.

```
dd if=/dev/zero of=/media/fimage.img bs=2048000

mdconfig -a -t vnode -f /media/fimage.img -u 2

mount /dev/md2 /mnt
```
All works fine but files and folders that exists before mounting md2 are disappeared after mounting .
Is there any option to make it possible merging the initial content of folder with the content of the mounted md2 !? 

Thanks


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## Alain De Vos (Sep 23, 2022)

Maybe,





						unionfs(8)
					






					www.freebsd.org
				



But it's dangerous ...


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## SirDice (Sep 23, 2022)

You can't mount md2, there's no partitioning on it and no filesystem. For all intents and purposes, it's a disk image. Treat is as a 'normal' disk. So partition and newfs(8) it (if you want UFS). 

You're trying to mount an empty disk (you wiped the whole thing with zeros).


```
root@molly:~/test # truncate -s 4G image.img
root@molly:~/test # ll
total 1
-rw-r--r--  1 root  wheel  4294967296 Sep 23 11:15 image.img
root@molly:~/test # mdconfig -a -f image.img
md0
root@molly:~/test # mount /dev/md0 /mnt/
mount: /dev/md0: Invalid fstype: Invalid argument
root@molly:~/test # gpart create -s gpt md0
md0 created
root@molly:~/test # gpart add -t freebsd-ufs md0
md0p1 added
root@molly:~/test # newfs /dev/md0p1
/dev/md0p1: 4096.0MB (8388528 sectors) block size 32768, fragment size 4096
        using 7 cylinder groups of 625.22MB, 20007 blks, 80128 inodes.
super-block backups (for fsck_ffs -b #) at:
 192, 1280640, 2561088, 3841536, 5121984, 6402432, 7682880
root@molly:~/test # mount /dev/md0p1 /mnt/
root@molly:~/test # ll /mnt/
total 8
drwxrwxr-x  2 root  operator  512 Sep 23 11:16 .snap/
root@molly:~/test # touch /mnt/helloworld
root@molly:~/test # ll /mnt/
total 8
drwxrwxr-x  2 root  operator  512 Sep 23 11:16 .snap/
-rw-r--r--  1 root  wheel       0 Sep 23 11:16 helloworld
root@molly:~/test # umount /mnt/
root@molly:~/test # mdconfig -d -u 0
```


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## bsaidus (Sep 23, 2022)

Eh, I just forget to write a full commands
Of course I've created a UFS fs for the md2 

```
newfs -O2 /dev/md2
```
After that I've mounted it and copied into it a folders and files.
But when I mount it in folder that initially contains files and folders, it masks that and display only content of /dev/md2


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## SirDice (Sep 23, 2022)

bsaidus said:


> But when I mount it in folder that initially contains files and folders, it masks that and display only content of /dev/md2


Yes, that's supposed to happen. What were you expecting to happen?


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## Alain De Vos (Sep 23, 2022)

It's called "overmounting".
If you want to see both you need to use the unionfs.


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