This is quite a common task for Linux system administrators, when it is needed to execute some command or a local Bash script from a one Linux workstation or a server on another remote Linux machine over SSH.
In this article you will find the examples of how to execute a remote command, multiple commands or a Bash script over SSH between remote Linux hosts and get back the output (result).
This information will be especially useful for ones, who want to create a Bash script that will be hosted locally on a one Linux machine but would be executed remotely on the other hosts over SSH.
SSH: Execute Remote Command
Execute a remote command on a host over SSH:
$ ssh USER@HOST 'COMMAND'
Examples
Get the uptime of the remote server:
$ ssh root@192.168.1.1 'uptime'
Reboot the remote server:
$ ssh root@192.168.1.1 'reboot'
SSH: Run Multiple Remote Commands
In the most cases it is not enough to send only one remote command over SSH.
Much more often it is required to send multiple commands on a remote server, for example, to collect some data for inventory and get back the result.
There are a lot of different ways of how it can be done, but i will show the most popular of them.
Run multiple command on a remote host over SSH:
$ ssh USER@HOST 'COMMAND1; COMMAND2; COMMAND3'
– or –
$ ssh USER@HOST 'COMMAND1 | COMMAND2 | COMMAND3'
– or –
$ ssh USER@HOST << EOF COMMAND1 COMMAND2 COMMAND3 EOF
Examples
Get the uptime and the disk usage:
$ ssh root@192.168.1.1 'uptime; df -h'
Get the memory usage and the load average:
$ ssh root@192.168.1.1 'free -m | cat /proc/loadavg'
Show the kernel version, number of CPUs and the total RAM:
$ ssh root@192.168.1.1 << EOF uname -a lscpu | grep "^CPU(s)" grep -i memtotal /proc/meminfo EOF
SSH: Run Bash Script on Remote Server
The equally common situation, when there is some Bash script on a Linux machine and it needs to connect from it over SSH to another Linux machine and run this script there.
The idea is to connect to a remote Linux server over SSH, let the script do the required operations and return back to local, without need not to upload this script to a remote server.
Certainly this can be done and moreover quite easily.
$ ssh USER@HOST 'bash -s' < SCRIPT
Example
Execute the local script.sh on the remote server:
$ ssh root@192.168.1.1 'bash -s' < script.sh
