write a shell script to ssh to a remote machine and execute commands

Question

I have two questions    There are multiple remote linux machines  and I need to write a shell script which will execute the same set of commands in each machine   Including some sudo operations   How can this be done using shell scripting   When ssh ing to the remote machine  how to handle when it prompts for RSA fingerprint authentication     The remote machines are VMs created on the run and I just have their IPs  So  I cant place a script file beforehand in those machines and execute them from my machine

User · Answer

If you are able to write Perl code  then you should consider using Net  OpenSSH  Parallel   You would be able to describe the actions that have to be run in every host in a declarative manner and the module will take care of all the scary details  Running commands through sudo is also supported

User · Answer

You can follow this approach     Connect to remote machine using Expect Script  If your machine doesn t support expect you can download the same  Writing Expect script is very easy  google to get help on this  Put all the action which needs to be performed on remote server in a shell script  Invoke remote shell script from expect script once login is successful

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For this kind of tasks  I repeatedly use Ansible which allows to duplicate coherently bash scripts in several containets or VM  Ansible  more precisely Red Hat  now has an additional web interface AWX which is the open-source edition of their commercial Tower   Ansible  https   www ansible com   AWX https   github com ansible awx  Ansible Tower  commercial product  you will probably fist explore the free open-source AWX  rather than the 15days free-trail of Tower

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There are multiple remote linux machines  and I need to write a shell script which will execute the same set of commands in each machine   Including some sudo operations   How can this be done using shell scripting    You can do this with ssh  for example      bin bash USERNAME someUser HOSTS  host1 host2 host3  SCRIPT  pwd  ls  for HOSTNAME in   HOSTS    do     ssh -l   USERNAME    HOSTNAME     SCRIPT   done      When ssh ing to the remote machine  how to handle when it prompts for RSA fingerprint authentication    You can add the StrictHostKeyChecking no option to ssh   ssh -o StrictHostKeyChecking no -l username hostname  pwd  ls    This will disable the host key check and automatically add the host key to the list of known hosts  If you do not want to have the host added to the known hosts file  add the option -o UserKnownHostsFile  dev null   Note that this disables certain security checks  for example protection against man-in-the-middle attack  It should therefore not be applied in a security sensitive environment

User · Answer

This work for me   Syntax   ssh -i pemfile pem user name ip address  command 1   command 2  command 3       bin bash  echo              connecting to server and run commands in sequence              ssh -i    ssh ec2 instance pem ubuntu ip address  touch a txt  touch b txt  sudo systemctl status tomcat service

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Install sshpass using     apt-get install sshpass then edit the script and put your linux machines IPs  usernames and password in respective order  After that run that script  Thats it   This script will install VLC in all systems      bin bash SCRIPT  cd Desktop  pwd   echo -e  PASSWORD    sudo -S apt-get install vlc  HOSTS   192 168 1 121   192 168 1 122   192 168 1 123   USERNAMES   username1   username2   username3   PASSWORDS   password1   password2   password3   for i in    HOSTS       do      echo   HOSTS i        SCR   SCRIPT PASSWORD   PASSWORDS i         sshpass -p   PASSWORDS i   ssh -l   USERNAMES i     HOSTS i      SCR   done

User · Answer

This worked for me  I made a function  Put this in your shell script   sshcmd        ssh  1  2  3    sshcmd USER HOST COMMAND   If you have multiple machines that you want to do the same command on you would repeat that line with a semi colon  For example  if you have two machines you would do this   sshcmd USER HOST COMMAND   sshcmd USER HOST COMMAND   Replace USER with the user of the computer  Replace HOST with the name of the computer  Replace COMMAND with the command you want to do on the computer   Hope this helps

User · Answer

There is are multiple ways to execute the commands or script in the multiple remote Linux machines  One simple  amp  easiest way is via pssh  parallel ssh program     pssh  is a program for executing ssh in parallel on a number of hosts  It provides features such as sending input to all of the processes  passing a password to ssh  saving the output to files  and timing out   Example  amp  Usage     Connect to host1 and host2  and print  hello  world  from each      pssh -i -H  host1 host2  echo  hello  world    Run commands via a script on multiple servers      pssh -h hosts txt -P -I lt   commands sh   Usage  amp  run a command without checking or saving host keys     pssh -h hostname ip txt -x  -q -o StrictHostKeyChecking no -o PreferredAuthentications publickey -o PubkeyAuthentication yes  -i   uptime  hostname -f    If the file hosts txt has a large number of entries  say 100  then the parallelism option may also be set to 100 to ensure that the commands are run concurrently     pssh -i -h hosts txt -p 100 -t 0 sleep 10000   Options   -I  Read input and sends to each ssh process    -P  Tells pssh to display output as it arrives    -h  Reads the host s file    -H    user  host  port  for single-host    -i  Display standard output and standard error as each host completes   -x args  Passes  extra SSH command-line arguments    -o option  Can be used to give options in the format used in the configuration file   etc ssh ssh config      ssh config    -p parallelism  Use the given number as the maximum number of concurrent connections   -q Quiet mode   Causes most warning and diagnostic messages to be suppressed    -t  Make connections time out after the given number of seconds  0 means pssh will not timeout any connections       When ssh ing to the remote machine  how to handle when it prompts for   RSA fingerprint authentication    Disable the StrictHostKeyChecking to handle the RSA authentication prompt    -o StrictHostKeyChecking no   Source  man pssh

User · Answer

There are a number of ways to handle this   My favorite way is to install http   pamsshagentauth sourceforge net  on the remote systems and also your own public key   Figure out a way to get these installed on the VM  somehow you got an entire Unix system installed  what s a couple more files    With your ssh agent forwarded  you can now log in to every system without a password   And even better  that pam module will authenticate for sudo with your ssh key pair so you can run with root  or any other user s  rights as needed   You don t need to worry about the host key interaction  If the input is not a terminal then ssh will just limit your ability to forward agents and authenticate with passwords   You should also look into packages like Capistrano  Definitely look around that site  it has an introduction to remote scripting   Individual script lines might look something like this   ssh remote-system-name command arguments       so  for exmaple  ssh target mycorp net sudo puppet apply

[linux] write a shell script to ssh to a remote machine and execute commands

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