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I have a 64-bit server running linux 3.x that reports "bash: fork: cannot allocate memory". This server has plenty of RAM (64G) and swap (128G) and I cannot see a particular process being the culript (no apparent memory leak).

I was not limited by "ulimit" as nothing was running under this shell, and the problem also existed as root. It is slightly complicated to debug a server when even typing top or cat /proc/whatever fires "bash: fork: cannot allocate memory" 95% of the time.

A few check I already did: - some memory was remaining (total allocated space less than swap space). - no ulimit - no clear issue, no messages in log, no messages in dmesg - virtual memory not exhausted (as far as I checked)

What should I check when I encounter this same problem again ? What can be the causes of no possible memory allocation apart ulimit / limited swap space / non exhausted virtual space ? Of course a reboot solved the issue (for now) but I am pretty surprised by this issue.

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  • Even ulimit -a shows unlimited to max user processes, virtual memory and file locks? (last 3 lines of the output). On my workstation for example, i have the max user processes (-u) 62636 and this could be a problem but a good way to limit the action of a fork bomb...
    – user34720
    Jan 5, 2015 at 22:45

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I believe the issue to be related to a Windows mount request gone bad. When the Unix forked process gets the message back from Windows, there appears to be a fumble of sorts.

This dominoes into other realms where resource "A" is requested directly or indirectly. I've seen it most recently with respect to VM related events.

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