Mount and access external media
Once Raspberry Pi OS is installed and running, a default 'pi' user is created. I have a SSD drive in USB 3.0 enclosure plugged in. Every time after booting up, it is mounted under /media/pi/label.
I have another user foo, as there are several users for this box and I don't wait to use the default 'pi'. And I added user foo in root group for root group privilege.
Problem: I can't go to /media/pi to access the SSD drive
To find the problem, first thing:
~$ ls -l /media drwxr-x---+ 2 root root 4096 Jun 21 14:19 pi
So it looks all good, root group has r-x access. However there is a '+' at end of the permission. What is it? Maybe something hidden there. I found the answer by searching online. We need the ACL tool getfacl/setfacl to find out:
~$ <code>sudo apt-get install acl</code> ~$ getfacl /media/pi # file: media/pi # owner: root # group: root user::rwx user:pi:r-x group::--- mask::r-x other::---
Now it is clear. Group members don't have any access right. The r-x is just the mask. So to grant access to group members:
~$ sudo setfacl -m g:root:rx /media/pi ~$ getfacl /media/pi
# file: pi # owner: root # group: root user::rwx user:pi:r-x group::--- group:root:r-x mask::r-x other::---
Now user foo in group root is able to access /media/pi and the mounted external SSD drive under it.