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== Problem: Startup == #1988
Rainbow needs to be started before the first activity is started, so that it
can be ready to go when Sugar starts launching activities.
Presently:
The startup sequence looks something like:
1. `/etc/inittab' specifies that the default runlevel is 5.
2. Upon entering runlevel 5, the DBus system daemon is started with priority
22.
3. `/etc/inittab' specifies that `/sbin/olpc-dm' should be started on
runlevel 5.
4. `/sbin/olpc-dm' does some basic configuration of the terminal, language
environment, and the session (e.g. does a PAM login); then it logs in as
user `olpc' and runs `startx'.
5. `startx' runs `xinit' which reads through /home/olpc/.xinitrc, does some
further graphical configuration, and then exec's `sugar'.
6. `sugar' is a script that uses `dbus-launch' to start the DBus session daemon.
7. The session daemon, once started, runs its argument `sugar-shell' with
appropriate environment variables.
8. `sugar-shell' brings up Sugar.
NB: Blizzard suggests that the current startup is hackish and should be
changed.
* In particular, we should use something less vulnerable to
modification than .xinitrc to start up.
* Also, he said that rc-scripts are going away to be replaced by a
monolithic start script.
Plan:
In the first iteration, we will simply launch Rainbow via rc-script at a
higher priority than `messagebus'. Since `sugar-shell' presently records its
DBus session bus's address to a `session.info' file, we will simply read this
file to acquire access to the main DBus session bus.
Followup:
Ivan suggests that we use `init' to start and respawn Rainbow.
"Creating an Unkillable Process", Silas Brown, Linux Gazette #139, 2007
http://linuxgazette.net/139/brownss.html
gives a nice overview of how to do this in a hardened way.
In the longer term, we may want to make the session bus talk to Rainbow in
some other fashion, for example by enclosing `sugar-shell' in a security stub
or by bringing the session bus up entirely separately from X.
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