There are a number of factors at play here:
1. Preinstallation (Linux does not have deals with major manufacturers so they are not generally installed by default on computers or even a choice when purchasing)
2. Familiarity (People use what they're used to don't like to migrate)
3. Software incompatibility (Some software will not run on Linux; this software might be highly desired or necessary for the users)
4. Perceived difficulty (Linux has origins in the programmer/hobbyist communities and the misconception that installing/running linux is difficult persists)
5. Lack of support (unless you are using an enterprise Linux [ex RHEL], there is no official corporate support. Trouble shooting must be done via wikis, forums, mailing lists etc.)
Widely used text-based operating system? Well, almost any Unix or Unix-like can be used in this way. X11 GUIs are an entirely optional application. Many Linux users only use the command line.
Operating systems using Linux are often found on servers, many popular sites' servers run Linux because of its stability and performance. Linux is also used by people wanting to learn how to build a kernel thru example, because Linux is open source, they can. Linux is also used by people who want to build a custom operating system for their needs.
In Linux the chmod command is used to set file permissions.
Usually a customized version of Linux.
Linus Torvalds was the principal engineer who created the Linux kernel, the chief component behind modern Linux operating systems used today such as Ubuntu, SUSE, or Fedora.
Absolutely. Very widely used. Actually, this very site runs on Linux...
No. Universities use Microsoft Windows.
The gtkpod software (See links below) is widely used for using an iPod with a Linux system.
Computer professionals that are running a dedicated webserver use dedicated Linux servers. Linux servers are currently the most widely used server operating systems in the world.
BIND is the default package for Domain Name service(DNS) in Linux based systems, one of the widely used DNS servers across the internet.
Tux is the unofficial but widely known mascot for the Linux kernel.
It's not really more vulnerable. Windows is more widely used so it has more viruses written for it.
Search Google with "jboss in Linux" for more info: Quote from jboss.org: JBoss, a free J2EE 1.4 certified application server, is the most widely used Open Source application server on the market. Unquote.
Yes, Linux can be used on a mainframe.
Widely used text-based operating system? Well, almost any Unix or Unix-like can be used in this way. X11 GUIs are an entirely optional application. Many Linux users only use the command line.
Linux hositng is cheaper because there is less data. Windows based hosting is more commonplace and widely used.
Computers need some kind of operating system; the most widely used is windows (from Microsoft). Other systems exist as well, such as Linux.