I have tried different OSes and found 'root' or 'Administrator' account in every system. Which is usually disabled by default. So what is purpose of this account? Why would we need this account? At what time it is created in any OS? If a 'root' account is necessary then why it is necessary, at what time OS use it?

closed as too broad by Anthon, Archemar, Networker, John WH Smith, jordanm Apr 2 '15 at 13:16

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    Read the wikipedia article on superuser. – Anthon Apr 2 '15 at 8:32
  • okay but that doesn't explain why root is necessary? OS can give all permissions to normal user for system task. – Osama Bin Omar Apr 2 '15 at 8:35
  • to keep it very short: root is used to separated management task (adding a disk or network interface) from user task (editing a document). – Archemar Apr 2 '15 at 8:42
  • @OsamaBinOmar Because if there was no separation between normal users and a root user, anybody accessing the system could access the kernel and subsequently control the hardware. You don't want that to happen do you? Especially not on a server where different users share resources. Your attempt of asking a good question is not really being successful. – Valentin Bajrami Apr 2 '15 at 8:46
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    @OsamaBinOmar Yes and I have used many a OS that do not have any destinction between "normal users" and root/superuser. As long as you don't care about, or don't have the time or knowledge to implement some level of security mechanism (e.g MSDOS) you can leave out the destnction. But I rather work unpriviliged when I don't have to, preventing my mistakes from escalating. – Anthon Apr 2 '15 at 8:53

That you found a root or Adminstrator account in every OS you looked at is just coincidence (or maybe a result of being new to this all). You don't need that kind of super-user in an OS and many OS don't have such a user or any concept of user at all. e.g. MSDOS.

If you (as the OS manifacturer) want to prevent all programs from doing everything without restriction, you need some way to require and allow privileges. There are many ways of doing this (flipping a switch on the front panel of a computer, inserting a card, logging in with super-user credentials).

The checks for this should be build into the OS. But the actual activation can be made depending on the circumstances. At install time, at activation at the users site, whatever is convenient, (or what the customer expects).

Not having a super-user (or other means to limit access to potentially destructive operations) can be considered user unfriendly as there is nothing between starting a (downloaded) program and it wiping your whole disk.

You don't need such a super-user, but once the mechanism is there (and correctly installed) you are better of using it. But then in order to elevate the privileges when circumstances require it you need some mechanism to check whether you are allowed to do get this "elevation". Logging in as root does the trick and is software only. If every computer in the world would have a switch on the front of the machine for super-user mode (not so secure if someone has physical access to your computer), or a secure-card slot and corresponding card, that could be used as a generic mechanism as well (but it would be difficult to download such a secure-card together with the installable ISO of your Linux, and thus less convenient).

  • I think any "serious" OS would have the concept of a superuser. – Faheem Mitha Apr 2 '15 at 15:30
  • @FaheemMitha I don't agree I have worked with serious OSes (OSen?) that had no concept of users (one of them only had users when you added a network interface and the corresponding ROM to the machine). On the other hand not every OS with a superuser concept can be considered serious. – Anthon Apr 2 '15 at 17:33
  • Ok, examples of such "serious" OSes? :-) Presumably not MS DOS. – Faheem Mitha Apr 2 '15 at 17:55
  • @FaheemMitha Acorn MOS allowed for plugable filesystems drivers (in ROM) as well as dual processor support (one 6502 for IO and a 6502/Z80/MC68000 or NS32016 for programs); DESQview/X which unfortunately lost out against Windows 3 – Anthon Apr 2 '15 at 19:17
  • I suppose Faheem meant to (correctly) observe that "serious" OSes invented after the 1980s would have the concept of a superuser. Indeed, the concept of a superuser originates from OSs developed before that time. Rationalising about ancient and obsolete systems serves little purpose, unless your purpose is solely to remind everybody that you're older and more experienced than the rest of us. – Lightness Races in Orbit Jan 22 '18 at 18:38

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