what do these names stand for 7375

Variable data. Traditionally Unix has been arranged so that andusr could be mounted read-only, so logfiles and other writable stuff had to be somewhere that could be mounted writable. Thusvar to hold things that couldn't be on read-only filesystems while the system was running.

Nobody's sure where the "user" reference came from. Traditionallyusr is where the bulk of the system software's installed. Back in the day when disks were small and reliability not so good, the root filesystem (and directories likebin,sbin etc.) was kept down to the minimum needed to actually boot the system.usr was a seperate filesystem on a different, larger disk, and got mounted during the boot process. The idea was that in an emergency you could boot the system and get to a single-user command prompt even ifusr wasn't available.

Related to this is the "bin" vs. "sbin" directories. Traditionallybin (andusr-bin etc.) have contained dynamically-linked versions of programs.sbin by contrast was where statically-linked versions of critical programs (that needed to work even when libc.so had been hosed) were put. Canonically the boot process would use the "sbin" versions so problems with system libraries wouldn't keep the box from booting, and "bin" would then be slipped into the path.

"Etcetera". Config files.

Pseudo-directory for process information.

Initial ramdisk. Not used during operation.

Optional software. This is a Sun oddity.

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