john.parnefjord.se Reflections & findings

I've been working with Nginx lately and spotted the error Too many open files in the error log. To deal with this I raised the number of files that the Nginx user (www-data) is allowed to open. By default only 1024 files are allowed to be opened. This may be checked by running these commands as user www-data:

ulimit -Hn
ulimit -Sn

The H and S refer to hard and soft values and the n switch to number of files. So to raise the limit a bit I added these lines in /etc/security/limits.conf:

www-data    hard    nofile    16384
www-data    soft    nofile    16384

The tricky part was to get the system to honour these values. For some reason the ulimit command still showed a value of 1024. The solution was to enable pam_limits in /etc/pam.d/su. I just uncommented the line:

session    required    pam_limits.so 

Changing this value didn't require a restart, I just logged in as www-data again. Running ulimit -a revealed the value 16384.