In the /etc/security/limits.conf file I increase, for example, the number of
open file handles allowed for a process.

# grep nofile /etc/security/limits.conf
dan        soft       nofile   10000
dan        hard      nofile   20000

In an SSH session I can verify the limits are being applied:

$ ulimit -n
10000


If, however, I setup a cron job as this user:

$ crontab -l
* * * * *  /bin/bash -c "ulimit > /tmp/ulimits.txt"

If I then look at the output the limits are not being applied

$ grep "open files" /tmp/ulimits.txt
open files              (-n)      1024


A little poking around reveals that the vixie-cron RPM is missing the PAM config
file neccessary to have session limits applied. If I create a file

# cat > /etc/pam.d/cron <<EOF
#%PAM-1.0
auth       required     pam_stack.so service=system-auth
account    required     pam_stack.so service=system-auth
password   required     pam_stack.so service=system-auth
session    required     pam_stack.so service=system-auth
EOF

Restart the cron daemon

# /etc/init.d/crond restart


Then, wait for the job to run again it now picks up limits correctly

$ grep "open files" /tmp/ulimits.txt
open files              (-n) 10000

The lack of this PAM config is causing application jobs that would otherwise
work, to fail