What are the default values of nproc in RHEL5 and RHEL6 and why are they different?

Environment

• Red Hat Enterprise Linux 6

Issue

• Why are the default values of nproc in RHEL6 different from RHEL4 and RHEL5?
• Where are the default soft limits of open process threads set in RHEL6?

Resolution

• In Red Hat Enterprise Linux 4 and 5, the default value of nproc is half of kernel.threads-max

# sysctl -a | grep threads-max
kernel.threads-max = 33024
    
# ulimit -u
16512

• While in Red Hat Enterprise Linux 6, the default value is not based on kernel.threads-max

# sysctl -a | grep threads-max
kernel.threads-max = 47819
       
# ulimit -u
1024

• Instead, the value is set to 1024 in /etc/security/limits.d/90-nproc.conf

    *          soft    nproc     1024

Root Cause

• Default limit for number of user's processes is used to prevent accidental fork bombs
• For more information: This content is not included.This content is not included.https://bugzilla.redhat.com/show_bug.cgi?id=432903

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