Questions[filesystem](ubuntu)

I found a 6 GB IDE HDD in my basement. I want to plug it in and see what might be on it. The drive seems to be recognized in BIOS.

I can't find it in Ubuntu to view files, and Ubuntu is the only OS on that particular computer. I was wondering if Ubuntu has an equivalent to the Windows feature "My Computer", which lists all available drives/storage devices. Typically, My Computer shows C:, which can be opened to view all of your directories and files. At this point, it is very similar to Ubuntu's Home Folder.

How to view/select all available partitions of that drive or all available HDD's without formatting or tampering with the contents in any way?

In Windows there’re perhaps only a couple of important folders (by important I mean important in my logical picture of the Windows file system) in the installation drive (in my case C:\). Namely Program Files and Windows. I simply stay away from Windows folder and the “add remove program files” is good enough to handle the program files folder of Windows. Of course there’s a folder named Users where the users (who are not admins) can access only their folders.

Thus there’s a clear picture at some level in my mind of the Windows file system. In Ubuntu, when I reach the location /, there’s a huge list of folders, most of which I have no clue as to what they contain. The /bin folder seems to be the equivalent of the Windows folder in windows. The /usr folder seems like it’s the equivalent of the Users folder in Windows. But even the /home folder looks like it can fit the bill.

Please understand that I do understand, that Ubuntu (Linux) has a different character than that of Windows, i.e., there need not be exact equivalent of Windows functions, in Ubuntu. All I am looking for is a bit more clearer picture of the Ubuntu file system.

_{This question is a part of a bigger question which I am splitting up to make it more answerable. The original question can be found here:
http://sgsawant.wordpress.com/2012/05/17/whats-the-equivalent-of-add-or-remove-programs-in-ubuntu/}

How is the /tmp directory cleaned up? Is it automatic? If so, how frequently is it cleaned up?

I'm planning on selling a USB external hard drive that currently contains an old Ubuntu installation with stored passwords and banking information.

How can I securely erase the drive before selling it?

Is there a simple command to display the total aggregate size (disk usage) of all files in a directory (folder)?

I have tried these, and they don't do what I want:

• ls -l, which only displays the size of the individual files in a directory, nor
• df -h, which only displays the free and used space on my disks.