JSch: Run command after Multi-Level ssh

Question

I am using JSch to run some commands after multi-level ssh:

public static void main(String[] args) {

    String user="User0";
    String ip="IP0";
    int port=22;
    String password="Password0";
            JSch jsch= new JSch();
            Session session=null;
            ChannelExec channel=null;
            try {
                session=(jsch.getSession(user, ip, port));
                session.setConfig("StrictHostKeyChecking", "no");
                session.setPassword(password);
                session.connect();
                String dir=Reomte_DIR;  
                String cmd1=SomeComplexCommand;
                String cmd2=SomeMoreComplexCommand;
                channel = (ChannelExec) session.openChannel("exec");
                channel.setInputStream(null);
                channel.setCommand("ssh User1@IP1_PasswordLessLogin;ssh User2@IP2_PasswordLessLogin; "+cmd1+" ; "+cmd2+" ;");
                channel.setPty(true);
                channel.connect(4000);
                String res = null;
                    BufferedReader input = new BufferedReader(new InputStreamReader(channel.getInputStream()));
                    BufferedReader error = new BufferedReader(new InputStreamReader(channel.getErrStream()));
                    if ((res = error.readLine()) == null) {
                        res = input.readLine()+input.readLine()+input.readLine()+input.readLine();
                    } else {

                        res = "-1";
                    }
                System.out.println("result:"+res);

            } catch (JSchException e) {
                e.printStackTrace();
            }catch (IOException e) {
                e.printStackTrace();
            }finally {
                channel.disconnect();
                session.disconnect();
            }       
        }

but it doesn't give desired result.

Infact channel.getInputStream() hangs. If I remove multilevel ssh, everything works fine! Am i doing something wrong??

I got some hint from: Multi-level SSH login in Java and Multiple commands using JSch but i am not able to get my code running.

Your command is wrong, did you try it on command line at all first? — Martin Prikryl, Nov 05 '16 at 18:29

Martin Prikryl · Accepted Answer · 2016-11-05T18:36:03.440

Your command is wrong.

Your command will execute the first command ssh User1@IP1_PasswordLessLogin.

And then it will wait for it to finish before executing the second command.

The first ssh command never finishes, as it will forever keep waiting for user to type commands.
Even if the first ssh ever finished, the second ssh would be executed on the initial host, not one the IP1.

You need something like this:

ssh User1@IP1_PasswordLessLogin ssh User2@IP2_PasswordLessLogin "<cmd1> ; <cmd2>"

This tells the first ssh to execute the second ssh on the IP1; and the second ssh to execute the <cmd1> ; <cmd2> on the IP2.

JSch: Run command after Multi-Level ssh

1 Answers1