Last summer, Carlos Villegas worked as part of the Google Summer of Code program to improve the debian Boot process. Part of his results were to identify what could be done to speed up the boot system. As can be seen from <URL:http://initscripts-ng.alioth.debian.org/soc2006-bootsystem/deliverable3.html>, the most effective single change was changing /bin/sh from bash to dash. The reason is that dash starts faster than bash, and the shell is started quite a lot of times during boot. Measurements showed that they run equally fast, so the improved boot time must be due to dash doing less work during initialization.
Ubuntu switched /bin/sh to dash several releases ago. I am not sure why, but suspect it was to speed up the boot. Debian Edu has been using dash as /bin/sh for several years now. The reason for switching was not boot speed, but the fact that bash loads libnss, which on a system using LDAP for NSS means all processes using /bin/sh would be linked to libldap in /usr/lib/, thus making it impossible to umount /usr/ during shutdown. Several Debian users use dash (popcon claim 18.57% have it installed and 5.50% used it last week), so most problems with bashism in shell scripts are already located and fixed. Switching to dash gave Carlos Villegas a 4 second (7.5%) speedup on his Etch test system. Such speedup would be very welcome in the generic Debian boot as well. To switch, the dash package need to be installed, and the debconf preseeding value to enable it need to be set: dash dash/sh boolean false Those wishing to switch back to bash can do so by running dpkg-reconfigure dash. Please consider making such switch a release goal or release target for Lenny. Happy hacking, -- Petter Reinholdtsen -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
