OPS145 Lab 2 Newversion

Multi-user systems

Linux was intended from its beginnings to be a multi-user system. A multi-user system allows multiple people to use it at the same time. That concept is hard to understand if you think of a computer as having one screen, one keyboard, and one mouse.

But originally systems like Unix (the Linux predecessor) were used as workstations by multiple people at once. They got around the problem of sharing one monitor and one keyboard by using dumb terminals. A dumb terminal might look like a computer but it isn't. It's just a screen plus a keyboard plus a serial port connection (like a slow network connection) to the actual computer (sometimes called a mainframe).

Other systems like Microsoft DOS (which eventually got a graphical interface and was then called Windows) had no such capabilities, and were much simpler. That made them the perfect choice for this new thing called a Personal Computer (PC). You didn't need much sysadmin training to put DOS on a PC.

For decades the mainframe was powerful enough to serve the needs of all the employees, but cheap enough that it wasn't going to get replaced with personal computers for each employee.

Eventually PCs got much cheaper, and since it was no longer financially viable to stick to mainframes: Microsoft took over the computer world with its DOS and later Windows operating systems.

Why terminals still exist

It turns out that when you create an operating system intended to be used by one user on their personal computer: you don't consider security or even multi-tasking performance as priorities.

In the 1980s and 1990s the entire world was plagued by viruses, blue screens of death, and abysmal server performance because the demand for IT increased exponentially but Unix was expensive, and Unix administrators were hard to find.

• Why terminals exist
• Linux is a natural multi-user system
• Types of things you can do in a terminal
• Look in home directory and subdirectories in Nemo and terminal (ls, ls -l, ls -l -h, cd, pwd)
• File not found, permission denied error exampls
• Create some text files in Xed, view them with cat
• Case sensitivity examples
• Download example files using firefox
• View a long text file in Xed, cat, less
• Plain text files vs doc files; plain text vs xls; file command
• Different image types, can't view in terminal, can check with file command
• Extensions mostly don't matter in linux
• Linux filesystem structure: one root, common directories