How to sudo su; then run command

Question

Can anyone help me to to solve following issue

i need to ssh to another server by e.g. ubuntu user which has permission to run sudo su fore sure then execute pm2 restart command

full command look like this

#!/bin/sh
CMD="sudo su; pm2 restart 0; pm2 restart 1; exit;"  
ssh -i somepemfile.pem [email protected] $CMD

for example i can run normally any command with sudo

CMD="sudo /etc/init.d/apache2 restart"  

but with sudo su case it somehow hang and do not response

Fidellas

Answer 1

Unless you have an unusual setup, you can't normally string su with other preceding commands like that. I would imagine it is running sudo su, then hanging in the root environment/session, because it's waiting for you to exit before preceding to the pm2 commands. Instead, I would consider something along the lines of this using the -c option:

CMD="sudo su -c 'pm2 restart 0; pm2 restart 1'"
ssh -i somepemfile.pem [email protected] "$CMD"

As suggested in another answer, it would also probably be useful to encapsulate the $CMD variable in quotes in the ssh call.

Somewise

Answer 2

su normally puts you in a sub shell which you can see by echoing the current PID (process id)

$ echo $$
94260
$ sudo echo $$
94260
$ sudo su
$ echo $$
94271

But to get around this you can pipe the commands you want to run to su like this

$ echo "whoami" | sudo su
root

And we run multiple commands

$ echo "uptime;whoami" | sudo su
11:29  up 8 days, 19:20, 4 users, load averages: 4.55 2.96 2.65
root

Now to make this work with ssh

$ ssh wderezin@localhost 'echo "uptime;whoami" | sudo su'
sudo: no tty present and no askpass program specified

Darn it, we need allocate a tty for the su command. Add the -t option which allocates a TTY during the remote execution.

$ ssh -t wderezin@localhost 'echo "uptime;whoami" | sudo su'
11:36  up 8 days, 19:26, 5 users, load averages: 2.97 2.97 2.76
root

Your command would look this

ssh -i somepemfile.pem [email protected] 'echo "pm2 restart 0; pm2 restart1" | sudo su'

Curly

Answer 3

Use -c option of su to specify the command

From man su

In particular, an argument of -c will cause the next argument to be treated as a command by most command interpreters. The command will be executed by the shell specified in /etc/passwd for the target user.

CMD="sudo su -c  \"pm2 restart 0; pm2 restart 1;\""

Cynical

This would be the answer for me but alas, su is passwordless but su -c is not. – Radley

Answer 4

You need to quote the expansion so that the entire string is parsed on the remote end.

ssh -i somepemfile.pem [email protected] "$CMD"

Otherwise, the expansion is subject to word splitting, and the remote shell gets a string which consists of the command sudo and the arguments su;, restart, 0;, pm2, restart;, 1;, and exit;. That is, ssh will escape the semicolons when it builds a single string from the separate arguments you pass.

However, that doesn't solve the problem of running pm2 in the shell started by sudo. That is addressed by ramki.

Luellaluelle