how to run multiple commands on a remote linux server using bash script

Question

I am currently writing the following script that logs into a remote server and runs couple of commands to verify the performance of the server and prints a message based on the output of those commands .But the ssh doesn't work and returns the stats of the server that hosts the script instead .

Script

#!/bin/bash
#######################
#Function to add hosts to the array
#the following function takes the ip addresses provided while the       script is run and stores them in an array
#######################
Host_storing_func () {
  HOST_array=()
  for i in $@ ;do
    HOST_array+=(${i});
  done
  #echo ${HOST_array[*]}
}

#######################
#Calling above function
#######################
Host_storing_func "$@"

############################################################
#Collect Stats of Ping,memory,iowait time test function
############################################################
b=`expr ${#HOST_array[*]} - 1 `
for i in `seq 0 $b` ;do
  sshpass -f /root/scripts/passwordFile.txt /usr/bin/ssh  student35@${HOST_array[${i}]}   <<   HERE
    echo `hostname`
    iowaittm=`sar 2 2|awk '/^Average/{print $5};'`
    if [ $iowaittm > 10 ];then
     echo "IO ==> BAD"
    else
     echo "IO ==> GOOD"
    fi
    memoryy=`free -m |grep Swap|awk '{if($2 == 0) print 0;else print (($4 /  $2 ) * 100)}'`
    if [ ${memoryy} < '10' ] ;then
     echo "memory ==> good"
    elif [[ "${memory}" -ge 0 ]] && [[ "${memory}" -le 10 ]];then
     echo "No Swap"
    else
     echo "memory ==> bad"`enter code here`
    fi
    ping -w2 -c2 `hostname` | grep "packet loss"|awk -F, '{print $3}'|awk -F% '{print $1}'|sed 's/^ *//'|awk '{if ($1 == 0) print "Yes" ;else print "No"}'
    HERE
done

Output : oc5610517603.XXX.com is the name of the source server

[root@oc5610517603 scripts]# ./big_exercise.sh 9.XXX.XXX.XXX 9.XXX.XXX.XXX
Pseudo-terminal will not be allocated because stdin is not a terminal.
oc5610517603.XXX.com 
IO ==> GOOD
No Swap
ping: oc5610517603.ibm.com: Name or service not known
Pseudo-terminal will not be allocated because stdin is not a terminal.
oc5610517603.XXX.com
IO ==> GOOD
No Swap
ping: oc5610517603.XXX.com: Name or service not known

Host_storing_func doesn't seem necessary; just use HOST_array=("$@") in its place. — chepner
– chepner, Commented Apr 2, 2018 at 17:19
Hi Biffen ,I made the change suggested by you it is helpful, but how do I fix the primary issue because the script is still being executed on the source server and not on remote. [root@oc5610517603 scripts]# ./big_exercise.sh 9.XXX.XXX.XXX 9.XXX.XXX.XXX Pseudo-terminal will not be allocated because stdin is not a terminal. oc5610517603.XXX.com IO ==> GOOD No Swap ping: oc5610517603.ibm.com: Name or service not known Pseudo-terminal will not be allocated because stdin is not a terminal. oc5610517603.XXX.com IO ==> GOOD No Swap ping: oc5610517603.XXX.com: Name or service not known — mourya nadella
– mourya nadella, Commented Apr 2, 2018 at 18:15

mourya nadella · Accepted Answer · 2018-04-03 20:22:10Z

1

thanks for checking the script , I figured out a way to solve the problem

It is the sshpass command that is causing issue , you just have to put the opening HERE in single quotes if you want to use variables with in the HEREdoc but if the variables are calculated before ssh then you don't have to put opening HERE in single quotes

sshpass -f /root/scripts/passwordFile.txt /usr/bin/ssh -T student35@${i} << 'HERE'

after I changed the sshpass command as above my script worked

answered Apr 3, 2018 at 20:22

mourya nadella

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1 Comment

Rakesh Gupta Over a year ago

Great. learned something new today! Glad that you figured it out. Best.

Rakesh Gupta · Accepted Answer · 2018-04-03 20:13:16Z

I have modified your script a bit.

As suggested by @chepner, I am not using the Host_storing_func. Heredocs for sshpaas are somewhat tricky. You have to escape every back-tick and $ sign in the heredoc.

Notice the - before the heredoc start, it allows you to indent the heredoc body. Also, try to avoid back-ticks when you can. use $(command) instead.

Hope it helps.

#!/bin/bash
#######################
#Function to add hosts to the array
#the following function takes the ip addresses provided while the       script is run and stores them in an array
#######################
array=( "$@" )
user="student35"

############################################################
#Collect Stats of Ping,memory,iowait time test function
############################################################

for host in ${array[@]}; do
    sshpass -f /root/scripts/passwordFile.txt /usr/bin/ssh -l ${user} ${host}  <<-HERE
    thishost=\$(hostname)
    echo "Current Host -> \$thishost";
    iowaittm=\`sar 2 2|awk '/^Average/{print \$5}'\`
    if [ \$iowaittm > 10 ]; then
        echo "IO ==> BAD"
    else
        echo "IO ==> GOOD"
    fi
    memory=\$(free -m | grep Swap | awk '{if(\$2 == 0) print 0;else print ((\$4 /  \$2 ) * 100)}')
    if [ \${memory} < '10' ] ;then
        echo "memory ==> good"
    elif [[ "\${memory}" -ge 0 ]] && [[ "\${memory}" -le 10 ]]; then
        echo "No Swap"
    else
        echo "memory ==> bad"\`enter code here\`
    fi
    ping -w2 -c2 \`hostname\` | grep "packet loss"|awk -F, '{print \$3}'|awk -F% '{print \$1}'|sed 's/^ *//'|awk '{if (\$1 == 0) print "Yes" ;else print "No"}'
    HERE
done

your script worked well for me , but I , made slight changes to my script and that worked for me

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