Innumerable. Remember that any program on Linux can be launched from the command line, so there are as many commands as there are programs.
There are many websites where one can learn about fdisk and many other Linux commands including Linux Help, Tuxfiles, Computer Hope, Linux Questions and Linux Solved.
useradd
utilities is nothing but predefined commands in linux
Linux and Unix and their variants have several different ways of locating files. each of the below commands can be used to locate files.findlocatewheriswhich
No. Linux is a free, open-source version of UNIX. Many of DOS's commands were based on UNIX commands, but the underlying operating system is much more powerful than DOS.
Many Linux users find the command line quicker than using the Graphic User Interface (GUI).
Depending on the OS and setup, they can be different. Look at the commands: info and man
There are many sources for this subject however one of the best are the cyberciti site. This site shows an extensive view of different operating systems run by Linux and allows the person to explore the site in great detail.
bash by default is configured to store the last 500 commands. You can configure it to store as many as you want, limited only by practicality and size, to whatever you want by setting the environment variable HISTFILESIZE to a different number.export HISTFILESIZE=2000
ls
There are no standardized commands for backing up a Linux system. Backup methods can range from dd to RAID to one of various backup utilities.
Yes. Just about everything to do with Linux on the command line is case sensitive, including commands and file names.