I have very little experience with linux, so maybe this is a dumb question :)
I run Ubuntu 24.04 on a machine, and I had an old HDD in a usb-case which I mounted using fstab. Worked fine, but I decided it wasn't appropriate for my purpose and removed it (physically and from fstab).
But it still shows up in the file manager? What am I missing?
I could be wrong but I thought fstab only runs those commands on boot? If so you'll need to manually unmount using "umount" for now. It shouldnt be there next reboot
Are you saying the drive still shows up on the side as ejectable? Or the mount directory is still there?
If the latter what directory is it mounted to? May just be as simple as deleting that directory if its empty. (Assuming its like /media/xxx/ or /mnt/yyy/)
Check with lsblk command if anything is in those directories
fstab is just a config file so the computer knows what drives and storage volumes its supposed to have when it boots.
You can add and remove drives without ever editing fstab. Plugging something in should give you the option to mount it in your file explorer, and in the same place you should be able to "eject" it before disconnecting the actual cable.
My guess is this is in GNOME? If there isn't an eject button next to the mount name, that's just a "favorites" link that got added, and not the actual mount. Right-click to remove it if you don't need it anymore.
With all due respect, RTFM. Mount and umount are two sides of the same operational coin. You mount the drive to use it and unmount it when you're done. fstab is just a file system table used to remember and consistently apply the options used whether you're mounting the drives manually or telling the system to do it at boot.
Deleting a line from fstab is not the same as unmounting, it is just a shortcut to tell the system how you want that drive mounted when you or the system run the mount command. Mount directories (usually the folders in /media/ or /mnt/ ) also do not get automatically deleted just because you "yanked the drive". Again, those directories are just where your system is expecting to mount the drive. When the drive is mounted they will be the root path to its contents, when the drive is unmounted they will be empty but they still exist. If your planning on mounting the drive again leave them there. If you're not planning on mounting them again, delete them.
If you're not planning on regularly mounting a particular drive, it probably shouldn't be listed in fstab and you should just run the mount command with the appropriate options (again fstab is just a table for remembering those options for the mount command).
Many desktop Linux distros are also capable of automatically mounting new removable drives in such a way that the user can access them and doesn't have to worry about touching fstab or the mount directories.
For me at least, it's not that you're asking questions. I answered, so obviously I'm sympathetic to confusion in this area. I'm just trying to encourage you to seek your answers in the documentation and manuals FIRST. The way your question was worded led me to believe that you had not read the manuals at all and were simply copying snippets of code and commands from some random question and answer style forum that did not teach you anything about the fundamentals of what those commands and code actually did. That's fine too, lots of people started off that way, myself included. Reading the manuals gives you the context to step back and understand how those commands work and what they're really doing. If you do, you'll be much better able to troubleshoot your own problems, you'll be able to ask better questions in forums like this, and you'll get better and more useful responses.