Just wondered, if there is no real files in /proc, why does it show up as the highest space occupier on my server (this is an old Solaris 2.6):

#du -sk * |sort -rn |head
723555 proc
302662 usr
282955 opt
249259 export
209532 var
8568 tmp
5997 kernel
5019 sbin
3965 platform
2536 etc

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I would appreciate a quick response, Thanks.