https://docs.services.mozilla.com/howtos/run-sync-1.5.html

Update the Server:

$ cd /path/to/syncserver
$ git stash       # to save any local changes to the config file
$ git pull        # to fetch latest updates from github
$ git stash pop   # to re-apply any local changes to the config file
$ make build      # to pull in any updated dependencies

Customize Firefox to use _your_ server

1. about:config
2. Search for services.sync.tokenServerURI
3. Replace the value with the sync server url that you have defined with a path of “token/1.0/sync/1.5, e.g. http://sync.example.com/token/1.0/sync/1.5

still Authentication is using Mozilla Servers now. so if you want to run a custom fxa-auth-server and fxa-content-server ^^ have fun:

 cd /pat/to/mozillasync
 git clone https://github.com/mozilla/fxa-auth-server/
 git clone https://github.com/mozilla/fxa-content-server/