Check Apache Stack Limit

Apache worker processes inherit their stack size from the system’s ulimit settings, and a misconfigured limit can cause segfaults or unexpected crashes under load. The command below pulls the actual stack limit from the kernel’s per-process view, so you see exactly what the running httpd process is using rather than what a shell session reports.

The Command

grep stack /proc/$(ps -fu nobody | grep httpd | awk '{ print $3 }' | tail -n 1)/limits

What It Does

1. ps -fu nobody lists all processes owned by the nobody user (the typical Apache worker user).
2. grep httpd filters to the Apache daemon processes.
3. awk '{ print $3 }' extracts the PID column.
4. tail -n 1 grabs the last PID (a representative worker).
5. grep stack /proc/<PID>/limits reads the kernel’s recorded resource limits for that process and prints the stack line.

Example Output

Max stack size                 8192                 8192                 bytes

The three columns are the soft limit, the hard limit, and the unit. A value of 8192 means 8 KiB, which is the common default. If you see unlimited, the process has no stack cap.

When to Check This

• After a segfault or SIGSEGV in a mod_php or mod_perl handler.
• When comparing a production host against a staging host that behaves differently.
• Before raising ulimit -s in an init script or systemd unit to confirm the change actually propagated to the worker.

• SysAdmin

• Bash
• SysAdmin