If you need to set up a passwordless SSH between multiple hosts, you can try the following script to do it automatically for you rather than manually copying the keys from one hosts to another.

The script needs an input file ip.txt that has server information for all hosts. The format of this file is:

ip.txt

Node_# IP_Address GW_Address FQDN
For example:
01 192.168.142.101 192.168.142.2 pnode01.purescale.ibm.local
02 192.168.142.102 192.168.142.2 pnode02.purescale.ibm.local
03 192.168.142.103 192.168.142.2 pnode03.purescale.ibm.local
04 192.168.142.104 192.168.142.2 pnode04.purescale.ibm.local

Create this ip.txt in your home directory. For root, it can be /root and for the user, it must be in the user’s home directory.

The script genSSH is as follows or download from here.

 
#Author : Vikram Khatri vikram [dot] khatri [at] us [dot] ibm [dot] com
#
# Purpose: Generate SSH keys
#

set +x

runrcmd()
{
     expect -c "
     set timeout 20
     spawn $1
     expect \"*assword:*\" { send \"$USERPW\r\" }
     expect \"(.*)\r\"
    " >> $LOGFILE
}

if [ $# -lt 4 ] ; then
    echo "Usage: $0 USER_NAME USER_PASSWORD USER_GROUP USER_HOME"
    echo "Usage: $0 root rootpassword root /root"
    echo "Usage: $0 db2psc userpassword db2iadm /home/db2psc"
    echo "Usage: $0 db2uat1 userpassword db2iuat1 /u01/home/db2uat1"
    exit 1
fi

USERNM=$1
USERPW=$2
USERGP=$3
USERHM=$4
SCHOME=/tmp
IPFILE=$HOME/ip.txt
KNOWN_HOSTS=$SCHOME/known_hosts
LOGFILE=$SCHOME/genSSH${USERNM}.log
SSH="/usr/bin/ssh -q -o StrictHostKeyChecking=no"
SCP="/usr/bin/scp -q -o StrictHostKeyChecking=no"

> $LOGFILE
> $KNOWN_HOSTS
############### Build server list from ip.txt #####
i=0
while read a b c d
do
  SHORTNM=${d%%.*}
  servers[$i]=$SHORTNM
  i=`expr $i + 1`
  echo Generate hosts keys for $SHORTNM
  ssh-keyscan $SHORTNM >> $KNOWN_HOSTS
  ssh-keyscan $d >> $KNOWN_HOSTS
  ssh-keyscan $b >> $KNOWN_HOSTS
  ssh-keyscan $b,$SHORTNM,$d >> $KNOWN_HOSTS
done < $IPFILE
echo "server list " ${servers[@]}

########################################################
for ((i = 0; i < ${#servers[@]}; ++i))
do
  server=${servers[$i]};
  echo Deleting ${USERHM}/.ssh on $server
  runrcmd "${SSH} $server \"rm -fr ${USERHM}/.ssh\""
  echo Generating private/public keys for ${USERHM}/.ssh on $server
  runrcmd "${SSH} $server \"ssh-keygen -t rsa -N '' -f ~/.ssh/id_rsa\""
  echo Sending known_hosts to the ${USERHM}/.ssh on $server
  runrcmd "${SCP} $SCHOME/known_hosts ${USERNM}@$server:${USERHM}/.ssh/known_hosts"
  echo Setting chmod 600 to ${USERHM}/.ssh/known_hosts on $server
  runrcmd "${SSH} $server \"chmod 600 ${USERHM}/.ssh/known_hosts\""
  echo Getting id_rsa.pub from ${USERHM}/.ssh on $server
  runrcmd "${SCP} ${USERNM}@$server:${USERHM}/.ssh/id_rsa.pub $SCHOME/${USERNM}.id_rsa.pub.$server"
done
> $SCHOME/authorized_keys.${USERNM}
for server in ${servers[@]};
do
  echo Combining id_rsa.pub from $server into authorized_keys
  cat $SCHOME/${USERNM}.id_rsa.pub.$server >> $SCHOME/authorized_keys.${USERNM}
  cat $SCHOME/${USERNM}.id_rsa.pub.$server >> $SCHOME/authorized_keys.${USERNM}
  echo Remove $SCHOME/${USERNM}.id_rsa.pub.$server
  rm -f $SCHOME/${USERNM}.id_rsa.pub.$server
done
echo Copying authorized_keys
for server in ${servers[@]};
do
  echo Copying authorized_keys of ${USERNM} to the $server
  runrcmd "${SCP} $SCHOME/authorized_keys.${USERNM} ${USERNM}@$server:${USERHM}/.ssh/authorized_keys"
  echo Setting chmod 600 to ${USERHM}/.ssh/authorized_keys on $server
  runrcmd "${SSH} $server \"chmod 600 ${USERHM}/.ssh/authorized_keys\""
  echo Remove $SCHOME/authorized_keys.${USERNM}
  runrcmd "${SSH} $server \"rm -f $SCHOME/authorized_keys.${USERNM}\""
done

Example: To set up passwordless SSH for root, run

 # ./genSSH root password root /root

The password in above is the root password and it must be same on all hosts that you are defining in /tmp/ip.txt

To setup passwordless for a user db2psc, login as db2psc and run

$ ./genSSH db2psc password db2iadm /home/db2psc

The password in above is the user password and it must be same on all hosts that you are defining in /tmp/ip.txt