Heh, of definitions.. pointless waste of time ;-) What i ment to say was that while Linux was based on the concepts of Mimix (which in turn was based on UNIX System V, which was derived from UNIX Time-Sharing-System Seventh Fifth Edition), it is an 'alike' implimentation and not 'Unix' internally...
Actually this is completely backwards -
Not only is Linux not based on minix, the differences in basic design philosophy between linux and minix were sharp enough to spawn a famous usenet thread on the disagreement between Linus T and Andrew Tannenbaum, the CS professor who wrote minix. According to Tannenbaum, Linux was designed all wrong, Linus was crazy, and he would have given him an F - meanwhile, 10 years later, Linux is moving into the data center, while minix is still an obscure academic toy.
IIRC, Linus referred to Maurice J Bach "The design of the unix operating system" while writing Linux - it was true that he borrowed the minix filesystem briefly just to quickly get something up and running, but discarded it early on, as soon as the ext filesystem was ready.
By the way, that was ext, not ext2, which came after xiafs -
just as linux is 'almost posix compliant' but not 'posix'.
The original unix was not posix either, so I'm not sure what that has to do with anything....
The internals that make linux != unix.
There are just as many difference in unix internals between different flavors of unix as there are between bsd and linux - both of which I consider unix. (but not "UNIX (TM)" which is completely a legal matter, not a technical one)
owell, i agree 'unix' by now has become a pop-art term for anything that looks, feels or smells like 'UNIX' type systems, thus almost become interchangable, however it's worth remebering that linux is 'only' a unix-alike and not a re-implimentation of unix.
It was a clean room re-implementation of unix in that Linus wanted a unix-like OS, but did not have access to the AT&T code - so he started with Bach and began buiding from scratch.
There's really nothing "pop-art" about it - There are some basic characteristics that signify a unix heritage, and are well known to those who grok the unix nature. I apologize for insulting the intelligence of those folk here, but for the sake of the newbies I'll enumerate a few of the characteristic signs of unix - no single one of these signs defines unix, but if you meditate on the whole picture, I believe you will eventually be enlightened.
1. Unix has a multiuser, client/server design 2. The Unix process model; init is the father of all processes 3. Each process has it's own protected environment 4. New processes creation is via fork, or fork/exec 5. Each process has a process id, a parent process, and a controlling tty 6. Processes become daemons by disconnecting from their controlling tty 7. Job control via nice, signals and foreground/backgrounding facilities 8. Each user has a unique user id and belongs to one or more a groups 9. There is a unique superuser with uid 0, not subject to normal limits. 10 Filesystem characteristics - quotas, hard/soft links, directory files 11 Files - The dir links inodes to filenames, inodes contain all other info 12 Filesystem layout - "/", transparent mount points, no "drive letters". 13 Overall filesystem hierarchy - /dev, /bin, /tmp, /var, /usr 14 Runlevels are an inherent facility - BSD has 3, SYSV has 7
Some other facts and features generally associated with unix while much less common in the whole non-unix world.
1. Generally recognizable as either SysV-ish or BSD-like 2. Generally includes a mail delivery system, c compiler, and debug tools 3. Philosophy of many small tools from which to build big tools 4. The native file sharing protocol is nfs, an open standard 5. Remote multiuser shell access via 'r' commands, secure shell, etc 6. Remote multiuser GUI access via network transparent X protocol 7. Generally standards-based, even if not open source
