how to run a script automatically in server soon after client system establish ssh connection with the server
for ex: suppose a user will logon to my computer from another system(connected via lan) using ssh connection. At that time, A script(python or shell) should be run automatically in my system to perform some validation?
How to run the script automatically in server system?
3 Answers
You can do so by adding the following parameter to your config file (/etc/ssh/sshd_config).
ForceCommand Forces the execution of the command specified by ForceCommand, ignoring any command supplied by the client and ~/.ssh/rc if present. The command is invoked by using the user's login shell with the -c option. This applies to shell, command, or subsystem execution. It is most useful inside a Match block. The command originally supplied by the client is available in the SSH_ORIGINAL_COMMAND environment variable. Specifying a command of “internal-sftp” will force the use of an in-process sftp server that requires no support files when used with ChrootDirectory.
An other option is to use the .ssh/rc files on a per user basis.
To use the ForceCommand method you just add ForceCommand /usr/bin/ownscript at the bottom of the file /etc/ssh/sshd_config (on the server).
The script looks like this:
#!/bin/bash
#Script file for ssh
#
#put your commands here
echo "test" > /tmp/test.txt
#
#exit by calling a shell to open for the ssh session
/bin/bash
Don't forget to chmod the script sudo chmod +x /usr/bin/ownscript
You can create a /etc/ssh/sshrc file. See man 8 ssh.
If you want this for a single user, use ~/.ssh/rc.
Here is a sample /etc/ssh/sshrc that will notify you via dbus when someone logs in on your machine. Don't forget to chmod +x:
#!/bin/bash
ip=`echo $SSH_CONNECTION | cut -d " " -f 1`
notify-send -u CRITICAL "SSH connection from ${ip}" "User $USER just logged in from $ip"
For execution of a script during logon, add it as a call from within the /etc/profile script. This is executed for every logon, not only for ssh logons.
