Synchronous remote file editing using SSH and Git
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xeno

README.md

UN(DER)MAINTAINED: This tool is essentially no longer maintained. Its design had some serious flaws with respect to growing repsitory size, inefficient polling, and slow synchronization. I've created something better now called Mutagen that might interest the same crowd (and perhaps even more people).

xeno

Build Status

xeno allows you to edit files and folders on a remote system using the editor on your local machine. It synchronizes data using Git and SSH, making it robust to connection dropouts and easily allowing you to work offline. Best of all, it runs entirely in user-space, so you can set it up and use it without complicated kernel modules or administrative privileges.

Features and basic usage

To start editing a remote path over SSH, use:

xeno edit user@hostname:/the/path

xeno will clone the remote path locally and keep it in sync with the remote copy, or, if you are already in an SSH session1, you can do:

xeno edit /the/path

and it will have exactly the same effect!

1: For in-session launches, you must use `xeno ssh`, a VERY thin wrapper around SSH which monitors console output for initialization messages ([FAQ](https://github.com/havoc-io/xeno/wiki/FAQs#isnt-it-insecure-to-use-the-xeno-ssh-wrapper)).

Extended usage

To view help information, use

xeno --help

xeno uses a variety of subcommands to do its bidding (e.g. config, edit, ...). To view help information for a particular subcommand, use:

xeno SUBCOMMAND_NAME --help

xeno supports the following subcommands:

  • edit: Starts editing sessions
  • list: Lists active xeno sessions
  • resume: Resumes a xeno session (opens your editor on the local copy)
  • stop: Stops a xeno session and cleans up local/remote resources
  • sync: Manually synchronizes a xeno session with the remote copy
  • ssh: A pass-through to 'ssh' which monitors console output for session initialization (see FAQ).
  • config: Manages xeno configuration information
  • daemon: Starts and stops the xeno daemon

To keep consistency, if you use the xeno edit command on a local path outside of an SSH session, it will simply open the local path in your editor. Thus, it is often convenient to alias the xeno edit command as something like xen, and use the xen command as a way to consistently launch your editor, both locally and remotely.

Requirements

xeno has a very minimal set of system dependencies, in particular:

  • A POSIX-compliant operating system and shell
  • OpenSSH
  • OpenSSL
  • Git 1.7.6+

Most systems meet the POSIX, OpenSSH, and OpenSSL requirements out of the box, and Git is generally going to be installed on most systems of interest. These requirements apply to both ends of the editing connection, though on the client side only OpenSSH client is required, and on the server side only OpenSSH server is required.

If there are issues, please let me know. I'd like to make things work on as many systems and shells as possible (within reason).

Installation

Before using xeno, it is strongly recommended (though by no means essential) that you set up SSH connection multiplexing. This allows you to persist SSH connections and re-use them, and will make SSH, Git, and xeno much faster for you. Instead of trying to give instructions here, I'll point you to this awesome article by Rackspace which gives an overview of the process.

The xeno program is a portable shell script, so you can simply download it from here and put it somewhere in your path. For example:

cd SOMEWHERE_IN_YOUR_PATH/
wget https://raw.githubusercontent.com/havoc-io/xeno/1.0.5/xeno
chmod a+x xeno

OS X users can alternatively install xeno via Homebrew:

brew install https://raw.githubusercontent.com/havoc-io/xeno/master/packaging/osx/homebrew/xeno.rb

You also need to launch the xeno daemon on the local end if you want automatic synchronization (you do not need to run the daemon on the remote end). The xeno daemon must be run on a per-user basis. The edit (both locally and inside an SSH session) and resume commands will automatically launch the local daemon if it is not running. You can manually start the daemon using the xeno daemon command (e.g. if you restart your computer and then don't use xeno resume). This command will not start another daemon if one is already running, so it is advised that you simply put this into your shell initialization script.

Finally, if you want in-SSH launch capabilities, you will need to install the xeno script in your path on the remote end, and on the local end you need to do:

alias ssh="xeno ssh"

The xeno ssh command is just a pass-through to SSH, but it monitors SSH's console output for initialization tokens. If this is a little too tin-foil-hat-inducing for you, you can still use the local launch mechanism without losing any sleep. For more information, please see the FAQ on this topic.

Configuration

xeno's configuration is managed via the 'xeno config' command. To print the current configuration, use:

xeno config

Configuration values can be set with:

xeno config key value

Configuration values can be viewed with:

xeno config key

Configuration values can be cleared with:

xeno config key --clear

xeno supports the following configuration keys:

  • core.editor: The editor command to use. If not set, xeno will fall back to the EDITOR environment variable.
  • sync.interval: The period, in seconds, for the daemon to wait between checks for local changes. The default is 10.
  • sync.force: By default, the daemon only checks for changes on the remote when pushing local changes. If this is set to "true", xeno will check the remote for changes every time it checks the local copy.

Implementation

The best way to understand xeno's implementation is to simply read it. It's only about 1,300 lines of shell script, which is organized roughly as:

# Constants
# Utility functions
# Initialization
# Individual command implementations
# Main entry/command-dispatch point

When xeno is invoked, it will generate an out-of-work-tree Git repository on the remote machine to track and coordinate changes. It installs some hooks in the remote repository to do some comitting/merging on the remote end every time a push is received from the local end. xeno will then clone the remote repository and launch your local editor on the clone. The basic repository synchronization flow looks like:

------------------------------------------------------------------------
|                                                               Editor |
------------------------------------------------------------------------
                                  |
                                  |
----------------------------------|-------------------------------------
|                                 |                   Local Repository |
|                                \|/       (non-bare, edited directly) |
|                              <master>                                |
|                               |   /|\                                |
--------------------------------|----|----------------------------------
                                |    |
 1: Local changes are committed |    | 3. Remote changes are pulled
    and pushed to the remote's  |    |    back to the local working
    incoming branch             |    |    copy, keeping the local copy
                                |    |    as canonical with '-X ours'
                                |    |
--------------------------------|----|----------------------------------
|                               |    |               Remote Repository |
|                              \|/   |        (bare, out-of-work-tree) |
|                       <incoming>   |                                 |
|                               |    |                                 |
| 2. post-receive hook commits  |    |                                 |
|    the remote master and      |    |                                 |
|    merges the incoming        |    |                                 |
|    changes into master,       |    |                                 |
|    keeping the incoming       |    |                                 |
|    changes as canonical with  |    |                                 |
|    '-X theirs'                |    |                                 |
|                              <master>                                |
----------------------------------|-------------------------------------
                                  |
                                 \|/
------------------------------------------------------------------------
|                                                          Remote Path |
------------------------------------------------------------------------

Because the remote Git repository is outside of the work tree, you can use it to edit remote folders which may already be Git repositories without any conflicts. xeno also works for editing single remote files. Best of all, because it uses Git, it will safely merge changes to and from the remote, and if your local editor is Git-aware, it will show you which files have or haven't been synced to the remote.

xeno provides a variety of commands for starting, managing, resuming, and ending sessions. xeno is robust, and the daemon will continue trying to sync changes to the remote repository even if SSH access becomes temporarily unavailable. When the editing session is ended, xeno will automatically clean up all local and remote resources.

More Information

For more detailed information, please see the xeno wiki and FAQs.

IMPORTANT NOTE

Early prototype versions of xeno prior to 1.0.0 were written in Python, and are not compatible with versions 1.0.0+. If you still require access to the older Python versions, you can install the last one with:

pip install git+https://github.com/havoc-io/xeno.git@0.0.5

Please note however that the Python version is no longer developed, supported, or even recommended. The shell version is simpler and has much better test coverage.