Mount can't find device in /etc/fstab

Why this error?

You probably forgot to tell mount where to mount your drive.

Linux uses device files (/dev/sda, /dev/sdb1, etc.). And unlike Windows drives (C:, D:, etc.), you cannot access them directly (cd /dev/sdb1 will inevitably fail, telling you that it is not a directory but a file). If you want to open a drive with mount, you need to provide a mountpoint. A mountpoint is a directory wherein your USB drive will be opened and where you will be able to access your files.

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Solution

1. Create a directory that you will use as the mountpoint for your drive:

   mkdir /mnt/mydrive
   

2. Mount your drive with this command:

   mount /dev/sdb1 /mnt/mydrive
   

   Note: If you don't know your drive's device file, you can run sudo fdisk -l or lsblk to identify the partition you're looking for.

3. Now if you run ls /mnt/mydrive, it should list your drive's files.

4. When you're done, don't forget to unmount your USB drive before removing it from the computer:

   umount /dev/sdb1
   

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More information about this error

/etc/fstab is a file in which you can associate a partition with a mountpoint, allowing you to run mount <device> instead of mount <device> <mountpoint>. This is why you get this confusing error.

fstab has many more uses like mounting a partition at boot time, etc. More information about fstab on the Arch Linux wiki