Tmux

Installation

Tmux is available in the package manager of most Linux distributions. Install it using whatever is appropriate for your system (e.g. apt install tmux, dnf install tmux, pacman -S tmux, etc).

Shared Session Configuration

The idea behind this was to allow easy pair programming in a fairly secure way using a separate unprivileged account to host the session. I've used a combination of tmux, some bash scripts, and sudo to accomplish this environment. Please note that I don't add the shared user to the 'sshers' group so there is only local access to the account.

User Setup

Create a new user, I used "shared" for the user name as shown in the example below. This will also create the "shared" group.

useradd shared
password shared

Set some ridiculous password for the user as no one will be logging directly in.

Add any users that you want to participate in the shared environment to the shared group like so:

usermod -a -G shared <username>

Add this line to the /etc/sudoers to allow any user added to the shared group to be able to switch to it without a password:

%shared   ALL=(ALL) NOPASSWD: /bin/su shared -

Shared Session Setup

Switch to the shared user's account from a user that is a member of the shared group and create a .bin directory in their home.

mkdir /home/shared/.bin

Inside of that create a file "shared-tmux" with the following contents and make it executable. This is a simplified version of a more flexible shared tmux session script I found on the Arch Linux Wiki which has a ridiculous amount of very good information that I strongly recommend people reference with any questions.

shared-tmux script

I added the following to the shared user's .bashrc file so the shared session pops open automatically as soon as a user has opened a shell and it will drop them out of the user's account as soon as they leave tmux.

if [[ -z "$TMUX" ]]; then
  export PS1="\W\$(__git_ps1)\$ "
  shared-session
  # The following is needed because funny shit happens when the server drops
  reset
  exit
else
  export PS1="[\u@\h \W]\$(__git_ps1)\$ "
fi

I also created a small shell script to make it easier for users to make use of the shared session in /bin/shared. The contents are below, make sure to make it executable:

#!/bin/bash

sudo su shared -
clear
echo "Left shared environment"

VIM & Tmux

I made a few compromises on my vim and tmux configuration to work with a co-worker and tried to keep it simple at the same time, so I'm including their configuration.

Here is the tmux configuration for /home/shared/.tmux.conf. There are two configuration items that are relevant to the shared session configuration and should be included even if you don't use any of the rest of it. The two relevant configuration lines are the setw -g aggressive-resize on and the set-option destroy-unattached on.

Here is the vim configuration I use for /home/shared/vimrc, nothing specifically related to the shared session in this one.