How to access an external drive
All volumes on internal or external hard disks/thumb drives/DVDs etc. are mounted to the directory /Volumes by default. The boot volume itself is linked as a soft link here.

Example:

user$ cd /Volumes/
...
dr-xr-xr-x   2 user      admin  -     12936 23 Nov 16:45 Audio-CD
drwxrwx---  14 user      admin  -       544 27 Okt 09:43 ExternalDrive
lrwxr-xr-x   1 root      admin  -         1 23 Nov 07:59 MacintoshHD -&gt; /
drwx------   1 user      staff  -       296 21 Nov 07:56 NetworkShare
drwxrwx---  14 user      admin  -       544 14 Okt 16:22 ThumbDrive
...


To access your thumb drive you have to enter cd /Volumes/name_of_thumb_drive.