Title: Mount a folder on another folder | |
Author: Solène | |
Date: 22 May 2018 | |
Tags: openbsd70 openbsd | |
Description: | |
This article will explain quickly how to bind a folder to access it | |
from another path. It can be useful to give access to a specific | |
folder from a chroot without moving or duplicating the data into the | |
chroot. | |
Real world example: "I want to be able to access my 100GB folder | |
/home/my_data/ from my httpd web server chrooted in /var/www/". | |
The trick on OpenBSD is to use NFS on localhost. It's pretty simple. | |
# rcctl enable portmap nfsd mountd | |
# echo "/home/my_data -network=127.0.0.1 -mask=255.255.255.255" > | |
/etc/exports | |
# rcctl start portmap nfsd mountd | |
The order is really important. You can check that the folder is | |
available through NFS with the following command: | |
$ showmount -e | |
Exports list on localhost: | |
/home/my_data 127.0.0.1 | |
If you don't have any line after "Exports list on localhost:", you | |
should kill mountd with `pkill -9 mountd` and start mountd again. I | |
experienced it twice when starting all the daemons from the same | |
commands but I'm not able to reproduce it. By the way, **mountd** only | |
supports reload. | |
If you modify */etc/exports*, you only need to reload **mountd** using | |
`rcctl reload mountd`. | |
Once you have check that everything was alright, you can mount the | |
exported folder on another folder with the command: | |
# mount localhost:/home/my_data /var/www/htdocs/my_data | |
You can add `-ro` parameter in the */etc/exports* file on the export | |
line if you want it to be read-only where you mount it. | |
Note: On FreeBSD/DragonflyBSD, you can use `mount_nullfs /from /to`, | |
there is no need to setup a local NFS server. And on Linux you can use | |
`mount --bind /from /to` and some others ways that I won't cover here. |