So actually you just want to mount a drive and use it as your steam library which is nothing to do with steam.
Before adding the mount to your fstab you should have mounted it manually then added it to fstab. So you’re sure it works.
First off make a mount point in your system it could be in your /mnt, /run/media, or /home. Let’s take /mnt (hope you have this folder physically in your / partition) because you already used that.
Make a folder using sudo mkdir /mnt/<your mount folder name>(If you already have done this you can skip this step).
Now you have got ownership of this folder otherwise your normal use won’t be able to read/write to this folder because at the moment it’s owned by your root user. You can do this using the below command. sudo chown -R <your user name>:<your user group name> /mnt/<your mount folder name> Ex:sudo chown -R shamshiel:shamshiel /mnt/<your mount folder nam>
Now you have to assign the permission for the folder. Like 777 (full read/write all), 755 (read/write/execute to the user and read/execute to the group and other), and 744 (read/write/execute to the user and read permission only to the group and other). Recommend using 744 and you can use the below command. sudo chmod -R 744 /mnt/<your mount folder name>
Do a ls -l /mnt this should show your mount folder named with the assigned permissions and it should look like this drwxr-r-r. Ex:drwxr-r-r 5 sinux sinux 4096 Sep 5 15:05 sinux1 ← This is one of my mount points.
Now you can add you mount point to fstab best use it like shown below. UUID=<your drives UUID> <your mount point folder name> ext4 noatime,x-systemd.automount,x-systemd.device-timeout=10,x-systemd.idle-timeout=1min 0 2
why use like this? answer below.
You should use systemd-automounts to mount external drives. That way it doesn’t matter if they are connected or not. It won’t impact your boot and you won’t have to manually mount them later. – @dalto
Now do a sudo mount -a to make sure there are no errors. If there’s none then do a reboot of the system and check if the drive is available in your file manager. Like below.
Now try to use this as your steam library. It should work.
And your drive seems to be owned by the root user group because your chown -R shamshiel /mnt/EVO850 is missing the user group. It should be sudo chown -R shamshiel:shamshiel /mnt/EVO850 and then sudo chmod -R /mnt/EVO850.