Re: Help file system basics??

In article <57g2j9$5se_at_preeda.internex.net.au> srinivas_at_connexus.apana.org.au (Srinivas Kopparapu) writes:
>
>Hi all,
>I am an ORACLE DBA on VAX/VMS platform and moving into AIX/UNIX
>area. Could someone please explain the filesystem concept and
>mounting of filesystem in UNIX. (In VMS we do not have a similar
>concept) I would really appreciate any help or pointers in the
>right direction.
>
>Is there any book on AIX basics and administration?
>
>TIA
>
>Sri
>srinivas_at_connexus.apana.org.au

If you recall your VMS, there is a MOUNT command that makes a device available for processing. This comes from the old days when you might want to change disk packs in your rpr02 on RSTS/RSX pdp 11/34. Since the same requirement existed for unix (basically because it is a hardware problem), a similar command does similar things. The filesystem concepts on unix are arguably a little simpler than the similar concepts on VMS.

A filesystem is a method of organizing files. The equivalent of a VMS device:[directory...] is a mount point and directories under them, separated by slashes. The root of all directories is simply a slash. Under that, you can have files and directories, which look the same unless you add switches to the list command to show which are which. For example, on VMS you might have DUA1:[ORACLE7.ORACLE_CODE_ROOT71.RDMS], while the equivalent unix system might have /d01/oracle/product/7.0.16/rdbms. This could have d01 defined as a mount point, so that it would be mountable at that point, you could take the disk on or offline. On the disk, you have the directory oracle, under that product, under that 7.0.16, underthat rdbms. Any of those directories could have other directories and files in it, so you may wind up with a complicated directory tree. Most unix can display the mount points with the fstab command.

The two most important differences between VMS and unix are: in unix, everything is considered to be a file; and "the unix way" is to break problems into small, easily defined problems, then write simple, reuseable tools that can be strung together to solve future problems.

There are zillions of books on unix and shell programming, so go to a bookstore and buy a few. There is more commonality between unix than differences, mostly because most of the code base is the same, and many utilities are written in shell languages that are similar across the platforms. The big exception is that major vendors have written programs for their system administration, that are completely different. The IBM program is superior to most in that it lets you access the shell commands that it is generating to do the work, so you can look and see what it is doing. The best reference is, of course, the books that come with the system. The best way to learn unix is to sit down with those books you bought and work through the examples. If you are in the situation of being thrown into unix administration of Oracle sink or swim, you might consider Oracle 7 Administration and Management by Ault, as it has a lot of cookbook procedures for both VMS and unix. Tricks of the Unix Masters by Sage has some pretty trick unix stuff, The Unix Programming Environment by Kernighan and Pike is the classic. When you start getting comfortable with the environment, Unix Power Tools by Peek, et al, can give hours of enjoyment, and you can even call it work.

When all else fails, there is always the man command.

You might try:

man hier
man -k file

-- 
Joel Garry               joelga_at_rossinc.com               Compuserve 70661,1534
These are my opinions, not necessarily those of Ross Systems, Inc.   <> <>
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