You can't use sudo to run ulimit like that. Instead, try $ sudo bash # ulimit -n 4096 # su jonypl $ ulimit -a (should show a raised limit on # of files) This is an awesome pain in the rear end, though, so you might want to find a way to raise this limit more permanently (e.g. by doing ulimit -n 4096 in /etc/rc.common, and rebooting; don't know if that works).