I have 4 hard drives. On the first one I have my operating system, that's fine. The others are empty with ext4 file systems. When I try to mount those with thunar (and xubuntu) it mounts those with root owner. Why?
Because they are still owned by root. You need to chown the new partitions.
You'll want to make sure the partitions are mounted, if you want to mount them at boot, then ensure they are set up in /etc/fstab.
The basic syntax for chown being
sudo chown user:group /path/to/partition
so if you're user/group is bert and the partition is mounted at /mnt/tmp then
sudo chown bert:bert /mnt/tmp
If you want to also deal with the access permissions for the partitions then chmod is you're friend.
To make the partition read/write/execute for user and group then
sudo chmod 770 /mnt/tmp
An excellent source of information for chmod - including a graphic representation tick box - http://ss64.com/bash/chmod.html
I found a permissions problem that cause Thunar to mount everything as root. There is a directory
/media/<username>/ that Thunar will attempt to use to mount volumes as your user. If this volume is not owned by you, it appears that Thunar reverts back to mounting volumes as root in locations such as
To fix this problem, just change the ownership of the directory in question to yourself:
sudo chown `whoami`:`whoami` /media/`whoami`/