Revision 18 as of 2007-03-16 16:50:19

Clear message


This spec discuss the inclusion and integration of a remote synchronization/storage/sharing solution in Edgy. The proposed solution is currently based on unison, although suitability of other tools (may be one of the version control systems, i.e. [ Mercurial]) should be considered.


Having a multiple computers configuration is more and more common everyday : one desktop at work, one desktop at home, one laptop. Keeping tracks of a given file or synchronization is often a real pain. Also, there's no easy way to share a file across the Internet if you don't have webserver and the knowledge of ftp/sftp.

Use cases

  1. Emma will soon fly to a conference in America with her whole new laptop. She wants to be sure that she can access all the necessary files that are on her home computer.
  2. Joe wants to share a 6 MB file with Jack. Unfortunately, his SMTP service will only allow mail messages that are less than 5 MB.
  3. William can never remember if a given file is on his laptop or desktop. Sometimes the file is on the desktop AND on the laptop, but he only wants the newest version.
  4. Sally has three computers, and wants a common home directory, including her Firefox extensions, and mail setup.


  • Decentralized model
  • 2 types of share public(no password)/private
    • A strong cryptography and security model - like SSH - for confidential data
    • A weak security model - read only - like anonymous ftp - for use case 2
  • Integration with the system file browser
  • On-demand file sharing and file synchronization
  • Display a list of available shares, their type and available actions


A special location in the file browser will show all nodes from LAN having files for sharing. Selecting a node will show all it's shares and right clicking a share will display a context menu with available actions (open, sync to, sync from)

Extended attributes or nautilus emblems should be used to mark folders for syncing/not syncing, public or private share, instead of the clumsy and incomprehensible Unison configuration files.

A configuration dialog would allow a default set of sync targets would enable a user to easily configure home dir syncing of things like firefox bookmarks/extensions (whole profiles, extensions, without caches!!!).

A configuration dialog could allow check box selection of what to sync between home folders (see above), and choose whether to sync video, music, or other large files. This could be bandwidth dependent, something which can be tested.

A wizard will allow a fast service setup enabling a default public share folder and default application synchronization (gaim, Firefox, evolution)


Existing solutions

  • ["iFolder"] , an open source solution from Novell would fit quite nicely.
  • [ Unison] a command line program that can keep multiple directories in sync. (even if there are changes on both) Works great, but would need a good nautilus extension (with a real gtk/gnome front end) to really make it amazing.

iFolder has disadvantages compared to Unison: it is less conservative in wiping data instead of adding new files. However, it is supported albeit semi-commercial, whereas Unison appears to be stagnant.

iFolder had a great disadvantages compared to Unison: you need the server part! In many use cases Ubuntu Linux is used just on the client side and the server side is some other GNU/Linux based distribution. Having a static build of Unison (for Linux, FreeBSD, Solaris) we will only need a valid ssh account on another computer.


  • based on openSLP [ info]

  • the "fshare" Service Agent will broadcast it's shares
  • the "fshare" User Agent will gather broadcasts from other "fshares".
  • the "fshare" application will make the information gathered by User Agent available at a "fshare://" location in the file browser.
  • Location "fshare://blinky" will display all shares provided by node "blinky". Depending of the share type opening a share will redirect the file browser to a scp:// or ftp:// location.

  • public file sharing is using ftp
  • private file sharing is using scp
  • File synchronization works on top of private file using unison

Data preservation and migration

Outstanding issues

BoF agenda and discussion

  • Added unison as existing solution
    • I use this program to keep my usb key in sync with a directory on my hard drive. This allows me to work on either and still sync the changes. The only minor issue is that if you change a non-text file on both directories you will have to decide which one to keep. It will not merge the differences. This program can keep complete backups if necessary and can merge more then two directories, in any order. Amazingly powerful it just needs a GUI and to be integrated into nautilus. -- PeterVanderKlippe DateTime(2006-04-24T13:23:53Z)

  • iFolder looks like a good product, but I think the enterprise mode server would be a bit much for Ubuntu's main purpose (though great for a server). The workgroup mode seems to be more appropriate, but it is not yet complete, according to Novell. It is also unclear how workgroup mode will work; to some extent it sounds like it will operate as extensions to chat clients and such. Also, a solution that can operate behind a firewall (and NAT) would be ideal, because, in my experience, many people are do not know how to modify the settings on their firewall/router (or can not because of their ISP). -- MatthewIsaacs DateTime(2006-04-27T01:16:14Z)

  • Unison seems like a good product. It currently works without the need for a central server, though it lacks a gui. A linux/Ubuntu gui could be modeled after gui for the windows version. The Unison FAQ points out some deficiencies that may arise in more complicated situations, such as sync loops and differences in timestamp granularity between different filesytems, and others. I'm not sure if iFolder has some of these problems or not. If Unison were used as a basis for the Ubuntu sync tool, some mechanism to handle this would probably have to be developed (though Unison does fail gracefully). -- MatthewIsaacs DateTime(2006-04-27T01:21:29Z)

  • Unison has a GUI, but not a great one. Unison is more ambivalent about filesystems than iFolder (which just takes charge in sometimes destructive ways).
  • Unison requires ssh login, and is relatively time consuming. iFolder syncs itself in the background with a saved login. Unison would need an unprivileged account with only access to the sync folder on the remote machine. iFolder watches the file system for changes and can sync more cleverly. A Unison daemon could run which watches inotify.
  • A lightweight http server could be use for file sharing instead of ftp allowing the use of webdav enabled applications

  • A further use case requiring something similar to iFolder enterprise mode would be: At work Anna has two computer (one laptop, one desktop) and a ssh account on the company's central server running a Unix-Like OS.The company sysadmin will not install any other software on the server. She wants to have it's application settings and documents synchronized (the newest version on each computer).

* Take a look at Conduit ( It does synchronization. Gshare handles file sharing already,