Shell script to SSH into another server and execute a script there

Question

I have 6 servers in my testing environment. I want to write a script to stop the Tomcat server in all boxes by logging into one box instead of logging into each and every box.

Please help me with shell scripting, SSH and executing a script in all other boxes. I use SSH with a password and custom port number.

Answer 1

You should combine two related Ask Ubuntu answers, one for logging into SSH via specific port and one for running commands on remote server , into one script. Of course, you'd need to have some form of data-structure to hold server+port correspondence. That could be either bash associative arrays or with POSIX shell script - a case statement. Assuming your username on all hosts is the same, we could come up with something like this:

#!/bin/sh
# bar host has ssh server on port 22, while baz - on port 2222
host_port(){
    case "$1" in
        "bar") echo 22 ;;
        "baz") echo 2222 ;;
    esac
} 

# set positional parameters of script to hosts and iterate over them
set -- bar baz
for host ; do
    # command substitution will call function, 
    # function's return value will be the port number
    ssh ssh://username@"$host":"$(host_port "$host")" -t "systemctl stop tomcat"
done

Now, a giant disclaimer: This is just an example. I don't have 6 servers to test the script, so adapt it to your needs as necessary. If you have different usernames on each host, use another case statement

---

Side note on logging in: if you have private key, which is accepted by all 6 servers it will be easy to log-in just by adding -i ~/.ssh/id_rsa. Alternative to that would be to create a ~/.ssh/config file with key/password information for each host. This is described in Lekensteyn's answer. If you're not familiar with SSH keys (and I understand it's kinda confusing topic), you might wanna read ssh.com article on the topic.

Answer 2

You can use sshpass:

sudo apt install sshpass -y 

then you can execute command on remote server, for example

    #!/bin/bash
    # login info
    HOST='192.168.0.1'
    USER='user'
    PORT='2222'
    PASSWORD='password'
    # command
    sshpass -p $PASSWORD ssh -p $PORT $USER@$HOST touch 1.txt