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Hi i heave heard that what ever we put on /dev/shm will be moved to ram disk.

I am having a situation where /dev/shm is 3 GB and / (5GB) became 100%,only file using that much space is /dev/shm resulting in reboot

i just mounted it by specifying it as tmpfs without specifying any size.

Can this cause files put into /dev/shm to appear on HDD rather than on ram resulting in disk becoming full.

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2 Answers 2

/dev/shm uses the shmfs filesystem, which uses VMM memory to simulate a disk volume.
If you have a swap file or partition, and try to populate the shmfs beyond what free memory you have available, it will swap.

Needless to say, you don't want this to happen; this is why shmfs is only 50% of your physical memory by default.

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but i am having 50GB ram space with 100% free space for swap only 5GB is allocated to / but for some reason / is 100% and /dev/shm using tmpfs file system consuming 3GB. –  kevin Jan 29 '13 at 12:59
    
So your problem probably lies elsewhere. What has increased usage in / ? –  mtm Jan 29 '13 at 14:00

I believe it will only drastically slow down your system.

More info here

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i am having enough ram,currently i am facing 100% / usage.i am using /dev/shm for saving DB sessions which became 3GB.Can there be any reason for disk to be used instead of ram? –  kevin Jan 29 '13 at 12:46

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