Add a new slave to a running pool and match the patch level.

# run the following commands on the new slave, replacing X.X.X.X with the IP of the existing pool's master:

MASTER_IP=X.X.X.X

ssh root@"$MASTER_IP" rpm -qa | sort > master-rpms.txt

rpm -qa | sort > local-rpms.txt

# determine the list of RPM versions present in master but not in the current host

comm -23 master-rpms.txt local-rpms.txt | tee updates.txt

# check the contents of the three files, especially updates.txt

# then feed it to yum update:

yum update $(cat updates.txt)