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Let's imagine that we have 8Gb of RAM on server. I'm mounting /dev/shm with 4Gb on board.

mount -o remount,size=4G /dev/shm

Will this memory be strictly reserved for shared memory or if /dev/shm is empty this memory could be used by regular applications (web server, php etc.)?

PS:Sorry for my English.

I'm asking it because I've just checked df -h and found tmpfs 6.0G 0 6.0G 0% /dev/shm on 8Gb RAM sever. I don't know who made this setup, but it seems to me awful.

Thank you!

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up vote 2 down vote accepted

No, it's not 'reserved'. It only uses as much RAM as needed. By default (if you don't specify size) it will be 50% the total RAM size.

You only need to worry if you're consistently filling it.

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@Javier, hello! Thank you for your answer. Please, could you tell me when I can read about it? – Kirzilla Apr 21 '10 at 12:01

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