MaxStartups and MaxSessions configurations parameter for ssh connections?
- by Webby
I am copying the files from machineB and machineC into machineA as I am running my below shell script on machineA.
If the files is not there in machineB then it should be there in machineC for sure so I will try copying the files from machineB first, if it is not there in machineB then I will try copying the same files from machineC.
I am copying the files in parallel using GNU Parallel library and it is working fine. Currently I am copying 10 files in parallel.
Below is my shell script which I have -
#!/bin/bash
export PRIMARY=/test01/primary
export SECONDARY=/test02/secondary
readonly FILERS_LOCATION=(machineB machineC)
export FILERS_LOCATION_1=${FILERS_LOCATION[0]}
export FILERS_LOCATION_2=${FILERS_LOCATION[1]}
PRIMARY_PARTITION=(550 274 2 546 278) # this will have more file numbers
SECONDARY_PARTITION=(1643 1103 1372 1096 1369 1568) # this will have more file numbers
export dir3=/testing/snapshot/20140103
find "$PRIMARY" -mindepth 1 -delete
find "$SECONDARY" -mindepth 1 -delete
do_Copy() {
el=$1
PRIMSEC=$2
scp david@$FILERS_LOCATION_1:$dir3/new_weekly_2014_"$el"_200003_5.data $PRIMSEC/. || scp david@$FILERS_LOCATION_2:$dir3/new_weekly_2014_"$el"_200003_5.data $PRIMSEC/.
}
export -f do_Copy
parallel --retries 10 -j 10 do_Copy {} $PRIMARY ::: "${PRIMARY_PARTITION[@]}" &
parallel --retries 10 -j 10 do_Copy {} $SECONDARY ::: "${SECONDARY_PARTITION[@]}" &
wait
echo "All files copied."
Problem Statement:-
With the above script at some point I am getting this exception -
ssh_exchange_identification: Connection closed by remote host
ssh_exchange_identification: Connection closed by remote host
ssh_exchange_identification: Connection closed by remote host
And I guess the error is typically caused by too many ssh/scp starting at the same time. That leads me to believe /etc/ssh/sshd_config:MaxStartups and MaxSessions is set too low.
But my question is on which server it is pretty low? machineB and machineC or machineA? And on what machines I need to increase the number?
On machineA this is what I can find -
root@machineA:/home/david# grep MaxStartups /etc/ssh/sshd_config
#MaxStartups 10:30:60
root@machineA:/home/david# grep MaxSessions /etc/ssh/sshd_config
And on machineB and machineC this is what I can find -
[root@machineB ~]$ grep MaxStartups /etc/ssh/sshd_config
#MaxStartups 10
[root@machineB ~]$ grep MaxSessions /etc/ssh/sshd_config
#MaxSessions 10
