Logged on as bryan@localserver, I'm trying to perform a backup using rsync on a remote host bryan@remoteserver.

I need the rsync connection to elevate privileges on the remote host using --rsync-path='sudo rsync', but I'm having problems, so have decided to simplify matters and just try to get the following working first:

bryan@localserver # ssh bryan@remoteserver 'sudo /usr/bin/whoami'

Once, I've cracked this, I should be able to get rsync working.

What I've done so far:

I've got ssh configured so that bryan@localserver can ssh to bryan@remoteserver using key instead of a password.

bryan@localserver # ssh bryan@remoteserver
bryan@remoteserver #

I've also configured bryan@remoteserver to be able to run /usr/bin/whoami as sudo, without a password in the sudoers file on remoteserver:

bryan   ALL=(ALL) NOPASSWD: /usr/bin/whoami

This works fine:

bryan@remotehost # sudo whoami
root

But from the local server:

bryan@localhost # ssh bryan@remoteserver 'sudo /usr/bin/whoami'
sudo: no tty present and no askpass program specified
Sorry, try again.
sudo: no tty present and no askpass program specified
Sorry, try again.
sudo: no tty present and no askpass program specified
Sorry, try again.
sudo: 3 incorrect password attempts

My complete sudoers file (minus the comments and blank lines) is below:

Defaults env_reset
Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
Defaults !requiretty
root    ALL=(ALL:ALL) ALL
bryan   ALL=(ALL) NOPASSWD: /usr/bin/whoami
%admin  ALL=(ALL) ALL
%sudo   ALL=(ALL:ALL) ALL

ssh -t from localserver solves the 'no tty present' error, but still prompts me for bryan@remotehost's password.

Can anyone please explain what the problem is?

localserver is Ubuntu 10.04 x64, remoteserver is Ubuntu 12.04 x64.