The host machine is Ubuntu 20.10 Desktop with VirtualBox version 6.1.16. The guest machine was also Ubuntu 20.10 Desktop with the latest (6.1.16) VB Guest Additions. I was able to use shared folders (shared from Host to Guest) from the "normal" Ubuntu user in the guest machine, since this user was also in the group
vboxsf and the shared folder was mounted in the guest machine with permissions
drwxrwx--- root vboxsf.
Now, after I upgraded (using
do-release-upgrade) the guest machine to 21.04, I am no longer able to access the shared folder from the normal user in the guest machine, because the shared folder is mounted with permissions
drwxr-x--- root root in the guest.
I tried to re-install GAs, with no change.
Nothing has changed on the host machine and a "clone" of the same old (20.10) guest works as expected (shared folders are mounted with permissions
drwxrwx--- root vboxsf as normal).
Note: As a side note, I need to mention that clipboard sharing also stopped working for the guest that was upgraded to 21.04.