The logrotate script uses

kill -SIGALRM `cat /var/run/hudson.pid`

which works fine for the bash builtin, but fails for /bin/kill, which only accepts

usage: kill [ -s signal | -p ] [ -a ] pid ...
       kill -l [ signal ]

on CentOS 5.

Using kill -s SIGALRM would make both variants happy and increase portability.