SSH and redirection

Question

Consider the following command

ssh aristotle sudo /bin/sh < test.sh

I want the redirection to apply to /bin/sh but it is consumed by sudo. Any ideas on how to achieve what I want?

Jonathan Gossage

Answer 1

Why not just copy over test.sh and then invoke it?

scp test.sh aristotle:/tmp/test.$$.sh
ssh aristotle sudo /bin/sh /tmp/test.$$.sh
ssh aristotle rm /tmp/test.$$.sh

The $$ is the PID of the process on the local machine, giving some degree of randomness so your file doesn't get clobbered.

Answer 2

Try this way:

ssh aristotle sudo /bin/sh -c "/bin/sh \\< test.sh"

Answer 3

houdini@www ~ % sudo "echo foo >> ~houdini/foo.$$"
sudo: echo foo >> ~houdini/foo.30055: command not found
houdini@www ~ % ls ~houdini/foo*
zsh: no matches found: ~houdini/foo*
houdini@www ~ % sudo -s "echo foo >> ~houdini/foo.$$"
houdini@www ~ % ls ~houdini/foo*
-rw------- 1 root root 4 Jul  8 20:16 /home/houdini/foo.30055
houdini@www ~ % sudo -i "echo foo >> ~houdini/foo.$$"
houdini@www ~ % ls ~houdini/foo*
-rw------- 1 root root 8 Jul  8 20:17 /home/houdini/foo.30055

Answer 4

I used ssh somehost sudo cat \< /etc/passwd with some success; try something like:

ssh aristotle sudo /bin/sh \< test.sh

Answer 5

Likely, sudo is prompting for a password and its trying to get it from your test.sh script.

There's two solutions.

First, you can assign NOPASSWD for your userid on the target system.

 your_username ALL=(ALL) NOPASSWD: ALL

Or second, you can ssh to the system and provide a password to sudo, then run it again and

$ echo "your_password" | ssh remote_host sudo -l
your_username@remote_host's password:
[sudo] password for your_username: 
User your_username may run the following commands on this host:
    (ALL) ALL
$ ssh remote_host sudo /bin/bash < test.sh
remote_host.example.com

Of course, you'll want to take precautions about your password appearing in your shell history (such as put it in a file only you have access to, then get the value from that file via cat or similar).

I strongly prefer the former, with SSH key-based authentication only, no passwords at all, and the private key residing on one system: my laptop (protected with a 16+ character passphrase).

Contents of my test.sh:

#!/bin/sh
hostname -f