Running Syncthing in a tmux Session

I run Syncthing to keep one of my KeePass databases in sync between multiple computers. (Here’s my “getting started” guide to using Syncthing.)

Before using tmux, I used to run Syncthing by opening a terminal and running syncthing -no-browser, then minimizing that terminal window for the day (the -no-browser flag tells Sycnthing not to launch the GUI dashboard in a browser tab). However, using tmux makes this flow a little smoother.

Our goal here is to run Syncthing “in the background”, so that we don’t have to keep a terminal window open with it running all the time. We also want to preserve the ability to easily stop Syncthing if we need to.

First, let’s install tmux. On macOS, I used Homebrew and ran brew install tmux. On Linux, sudo apt-get install tmux. Here’s “A Gentle Introduction to tmux” that I found helpful, but for this tutorial you’ll mostly be copying and pasting tmux commands into shell/bash functions.

Next, in your ~/.bash_profile or ~/.bashrc, add these two functions:

function ss {
  if tmux has-session -t synct 2>/dev/null; then
    echo "Syncthing session already started at http://127.0.0.1:8384/" >&2
    return 1
  fi
  
  echo "Starting up Syncthing at http://127.0.0.1:8384/"
  tmux new-session -d -s synct "syncthing -no-browser"
}

function se {
  if ! tmux has-session -t synct 2>/dev/null; then
    echo "No Syncthing session to end." >&2
    return 1
  fi
  
  echo "Stopping Syncthing and killing the tmux session"
  tmux send-keys -t synct C-c
}

To load these changes, run tmux source-file ~/.tmux.conf and then source ~/.bash_profile or source ~/.bashrc

Now you should be able to run ss in your terminal to Start Syncthing, and se to end Syncthing (“Syncthing End”).

(Thanks to @shello) who helped me add the conditionals and some unnecessary commands to the shell functions)

How I use these functions

So for me, when I boot up any of my computers, I just run ss in a terminal window. Syncthing runs in a tmux session, so I can either use that terminal window for something else or safely close it. If I need to stop Syncthing for any reason (which is rare) I can run se.

Appendix A: Some nice tmux settings if you’ll be using Vim and/or Neovim within tmux sessions

While we’re here, if you want to start doing any text editing with Vim or Neovim within tmux sessions, you may find these settings helpful. First, let’s create a tmux config file: touch ~/.tmux.conf. Enter this code into that file:

# in ~/.tmux.conf

# Neovim color help (https://github.com/neovim/neovim/issues/7764#issuecomment-411995268)
set -g terminal-overrides ',xterm-256color:Tc'
set -g default-terminal "tmux-256color"
set -as terminal-overrides ',xterm*:sitm=\E[3m'

# Set Neovim escape delay to 0 milliseconds (https://github.com/neovim/neovim/wiki/FAQ#esc-in-tmux-or-gnu-screen-is-delayed) 
set -sg escape-time 0

Appendix B: Simpler versions of the Syncthing shell functions

If the functions above are giving you problems, you can try these simpler versions I used at first:

# in ~/.bash_profile or ~/.bashrc
function ss {
  echo "Starting up Syncthing at http://127.0.0.1:8384/"
  tmux new-session -d -s synct
  tmux send-keys -t synct "syncthing -no-browser" Enter
}

function se {
  echo "Stopping Syncthing and killing the tmux session"
  tmux send-keys -t synct C-c
  tmux kill-session -t synct
}