Archive for September 2009
Show limits of a running process in Linux
A rather simple but often asked question was put forward to me today: How can I see the maximum amount of file descriptors my running process can open? (without killing the process!)
Typically one would say ‘check ulimit -n’ but lets say that a thread-driven or event-driven application like varnish or lighttpd is configured with an arbitrary amount of open file descriptors and you want to verify that they have taken effect before the application crashes.
A simple way to check this (atleast on Linux 2.6.26-1 or later) is to run:
svr1:~# awk '/Max open files/{ print $4}' /proc/$(pgrep -n lighttpd)/limits
1024
As you can see the above command returned the value of max open files for the running process. This means you can be sure that your lighttpd or varnish application will not suddenly die after being starved of file descriptors!
I have included the entire output of the limits table for the lighttpd process for completeness:
svr1:~# cat /proc/$(pgrep -n lighttpd)/limits Limit Soft Limit Hard Limit Units Max cpu time unlimited unlimited ms Max file size unlimited unlimited bytes Max data size unlimited unlimited bytes Max stack size 8388608 unlimited bytes Max core file size 0 unlimited bytes Max resident set unlimited unlimited bytes Max processes 5824 5824 processes Max open files 1024 1024 files Max locked memory 32768 32768 bytes Max address space unlimited unlimited bytes Max file locks unlimited unlimited locks Max pending signals 5824 5824 signals Max msgqueue size 819200 819200 bytes Max nice priority 0 0 Max realtime priority 0 0 Max realtime timeout unlimited unlimited us
Error: Device 0 (vif) could not be connected. Hotplug scripts not working
Are you running Xen / “xm create” and you get this error?
Try this (RHEL/CentOS): service haldaemon start
- and have a nice day!
