Bash Sudo Command Not Found

Maybe it isn't installed? Open your package manager and install the sudo package.

It looks from http://www.turnkeylinux.org/redmine like Redmine, unlike Ubuntu, does not use sudo by default. What username are you using to SSH in? If it's root, then you don't need to use sudo, as everything you do when SSHed in to the Redmine system is done as root. If it's something else, like admin, then you could try using the su command to get a root shell in which to run commands as root.

First login to your root account. Then

$ apt-get install sudo

Add your existing user to group sudo

$ sudo adduser <user> sudo

You should then login as <user>, and the sudo command should be there.