add unison article

system/unison.rst

@@ -0,0 +1,195 @@
+Working directly on your server? How to backup and sync your dev environment with unison
+########################################################################################
+
+:date: 16/03/2011
+:tags: freebsd, unison
+
+I have a server running freebsd since some time now, and was wondering about
+the possibility to directly have a development environment ready to use when
+I get a internet connexion, even if I'm not on my computer.
+
+Since I use vim to code, and spend most of my time in a console while
+developing, it's possible to work via ssh, from everywhere.
+
+The only problem is the synchronisation of the source code, config files etc.
+from my machine to the server.
+
+Unison provides an interesting way to synchronise two folders, even over
+a network. So let's do it !
+
+Creating the jail
+=================
+
+In case you don't use FreeBSD, you can skip this section.
+
+.. code-block:: bash
+
+    # I have a flavour jail named default
+    $ ezjail-admin -f default workspace.notmyidea.org 172.19.1.6
+    $ ezjail-admin start workspace.notmyidea.org
+
+In my case, because the "default" flavour contains already a lot of interesting
+things, my jail come already setup with ssh, bash and vim for instance, but
+maybe you'll need it in your case.
+
+I want to be redirected to the ssh of the jail when I connect to the host with
+the 20006 port. Add lines in `/etc/pf.conf`::
+
+    workspace_jail="172.19.1.6"
+    rdr on $ext_if proto tcp from any to $ext_ip port 20006 -> $workspace_jail port 22
+
+Reload packet filter rules
+
+.. code-block:: bash
+
+    $ /etc/rc.d/pf reload
+
+Working with unison
+===================
+
+Now that we've set up the jail. Set up unison on the server and on your client.
+Unison is available on the freebsd ports so just install it
+
+.. code-block:: bash
+
+    $ ssh notmyidea.org -p 20006
+    $ make -C /usr/ports/net/unison-nox11 config-recursive
+    $ make -C /usr/ports/net/unison-nox11 package-recursive
+
+Install as well unison on your local machine. Double check to install the same
+version on the client and on the server. Ubuntu contains the 2.27.57 as well as
+the 2.32.52.
+
+Check that unison is installed and reachable via ssh from your machine
+
+.. code-block:: bash
+
+    $ ssh notmyidea.org -p 20006 unison -version
+    unison version 2.27.157
+    $ unison -version
+    unison version 2.27.57
+
+Let sync our folders
+====================
+
+The first thing I want to sync is my vim configuration. Well, it's already `in
+a git repository <http://github.com/ametaireau/dotfiles/>`_ but let's try to use
+unison for it right now.
+
+I have two machines then: `workspace`, the jail, and `ecureuil` my laptop.
+
+.. code-block:: bash
+
+    unison .vim ssh://notmyidea.org:20006/.vim
+    unison .vimrc ssh://notmyidea.org:20006/.vimrc
+
+
+It is also possible to put all the informations in a config file, and then to
+only run `unison`. (fire up `vim ~/.unison/default.prf`.
+
+Here is my config::
+
+    root = /home/alexis
+    root = ssh://notmyidea.org:20006
+
+    path = .vimrc
+    path = dotfiles
+    path = dev
+
+    follow = Name *
+
+My vimrc is in fact a symbolic link on my laptop, but I don't want to specify
+each of the links to unison. That's why the `follow = Name *` is for.
+
+The folders you want to synchronize are maybe a bit large. If so, considering
+others options such as rsync for the first import may be a good idea (I enjoyed
+my university huge upload bandwith to upload 2GB in 20mn ;)
+
+Run the script frequently
+=========================
+
+Once that done, you just need to run the unison command line some times when
+you want to sync your two machines. I've wrote a tiny script to get some
+feedback from the sync:
+
+.. code-block:: python
+
+    import os
+    from datetime import datetime
+
+    DEFAULT_LOGFILE = "~/unison.log"
+    PROGRAM_NAME = "Unison syncer"
+
+    def sync(logfile=DEFAULT_LOGFILE, program_name=PROGRAM_NAME):
+        # init
+        display_message = True
+        error = False
+
+        before = datetime.now()
+        # call unison to make the sync
+        os.system('unison -batch > {0}'.format(logfile))
+
+        # get the duration of the operation
+        td = datetime.now() - before
+        delta = (td.microseconds + (td.seconds + td.days * 24 * 3600) * 10**6) / 10**6
+
+        # check what was the last entry in the log
+        log = open(os.path.expanduser(logfile))
+        lines = log.readlines()
+        if 'No updates to propagate' in lines[-1]:
+            display_message = False
+        else:
+            output = [l for l in lines if "Synchronization" in l]
+
+            message = output[-1]
+            message += " It took {0}s.".format(delta)
+
+        if display_message:
+            os.system('notify-send -i {2} "{0}" "{1}"'.format(program_name, message, 
+                'error' if error else 'info'))
+
+    if __name__ == "__main__":
+        sync()
+
+This is probably perfectible, but that does the job.
+
+Last step is to tell you machine to run that frequently. That's what `crontab` 
+is made for, so let's `crontab -e`::
+
+    $ * */3 * * * . ~/.Xdbus; /usr/bin/python /home/alexis/dev/python/unison-syncer/sync.py
+
+The `~/.Xdbus` allows cron to communicate with your X11 session. Here is its
+content.
+
+.. code-block:: bash
+
+    #!/bin/bash
+
+    # Get the pid of nautilus
+    nautilus_pid=$(pgrep -u $LOGNAME -n nautilus)
+
+    # If nautilus isn't running, just exit silently
+    if [ -z "$nautilus_pid" ]; then
+    exit 0
+    fi
+
+    # Grab the DBUS_SESSION_BUS_ADDRESS variable from nautilus's environment
+    eval $(tr '\0' '\n' < /proc/$nautilus_pid/environ | grep '^DBUS_SESSION_BUS_ADDRESS=')
+
+    # Check that we actually found it
+    if [ -z "$DBUS_SESSION_BUS_ADDRESS" ]; then
+    echo "Failed to find bus address" >&2
+    exit 1
+    fi
+
+    # export it so that child processes will inherit it
+    export DBUS_SESSION_BUS_ADDRESS
+
+And it comes from `here <http://ubuntuforums.org/showthread.php?p=10148738#post10148738>`_.
+
+A sync takes about 20s + the upload time on my machine, which stay acceptable for 
+all of my developments.
+
+.. image:: images/unison.png
+    :alt: the notify osd notification
+