Description of problem:

In RHEL 6, we can start multiple instances of crond just by running command "crond" in a shell, even if the service is already running. Every cron job gets executed multiple times, function of the number of crond process running.

This is not necessarily a bug. Multiple instances were prevented on RHEL5 / vixie-cron (see additional info).

Version-Release number of selected component (if applicable):

cronie-1.4.4-7.el6.x86_64

How reproducible:

Always

Steps to Reproduce:
1. service crond is running from boot time
2. ps -ef |grep crond show the 1 instance running
3. as root, type crond in a shell
4. ps -ef |grep crond show the 2 instances running
  
Actual results:

Every job get executed multiple times.
This is function of the number of crond process.

Expected results:

It would be good to prevent running crond in a shell if the service is already started.

Additional info:

RHEL 5 (good behavior)
----------------------

[root@pom-demo-30 ~]$ rpm -qa |grep vixie-cron
vixie-cron-4.1-81.el5

1 crond process running :

[root@pom-demo-30 ~]# ps -ef |grep crond
root       474   445  0 13:55 pts/0    00:00:00 grep crond
root      2851     1  0  2012 ?        00:00:03 crond

Start of another crond process prevented :

[root@pom-demo-30 ~]# crond
crond: can't lock /var/run/crond.pid, otherpid may be 2851: Resource temporarily unavailable

Still 1 crond process :

[root@pom-demo-30 ~]# ps -ef |grep crond
root       548   445  0 13:55 pts/0    00:00:00 grep crond
root      2851     1  0  2012 ?        00:00:03 crond

RHEL 6
------

[root@pom302 ~]# rpm -qa |grep cronie
cronie-noanacron-1.4.4-7.el6.x86_64
cronie-1.4.4-7.el6.x86_64

1 crond process running :

[root@pom302 ~]# ps -ef |grep crond
root      1274     1  0 14:00 ?        00:00:00 crond
root      1885  1865  0 14:00 pts/0    00:00:00 grep crond

Start of another crond process is *not* prevented :

[root@pom302 ~]# crond
[root@pom302 ~]# 

[root@pom302 ~]# ps -ef |grep crond
root      1274     1  0 14:00 ?        00:00:00 crond
root      2010     1  0 14:00 ?        00:00:00 crond
root      2096  1865  0 14:00 pts/0    00:00:00 grep crond