Jeni's Musings

Just a few points of clarification and elaboration.

(1) Some of this stuff is more or less specific to debian: for other linux distributions the file locations or commands may differ. In particular, the /etc/init.d/XXX start/stop stuff is part of debian’s excellent daemon/service control.

(2) When the little find script is run, as intended, in /etc/cron.hourly/, each invocation causes entries to be written to /var/log/syslog and /var/log/auth.log; so in interpreting the logs, these entries need to be ignored (if the script isn’t run, they won’t be there - Catch-22). When we no longer need to run the script, it should be removed from /etc/cron.hourly/ AND /etc/crontab should be edited by putting a hash (#) to comment out the “hourly” line - otherwise cron will still write an entry to the syslog every hour.

(3) Jeni seems worried about ntp waking the disk up in the middle of the night: I’m not. ntp is very clever about setting the local clocks, according to their tendency to drift and so on. After a while, it settles to setting the clocks relatively rarely, and just sometimes this is in the small hours. If we really want to stop this, we could turn ntp off (at 23:00 say) and on again (at 07:00, say), as with fetchmail and exim4 in Jeni’s method.

(4) For the record, the exim4 activity every 30 minutes is the frequency set in /etc/default/exim4 (I tend to forget this location of some system-wide configuration files in debian). If we were happy about exim4 running its queue less frequently, we could edit this (and then restart exim4); but we probably want exim4 to run its queue at least every 30 minutes during the day (perhaps more frequently, Jeni?) so it’s much simpler just to turn exim4 off at night.

(5) It would be perfectly possible to run samba, maybe stopping it overnight, to allow the slug to participate in Windows networking. However, samba is awfully complicated (see Linus’ comment in http://lwn.net/Articles/71521/) and quite annoying to configure; and Jeni’s requirement is “perfectly” fulfilled by using the much more solid ssh and sftp, with suitable Windows tools like sftpdrive and webdrive.

The slug (Linksys NSLU2) is a marvellous little device: functional PC with wired ethernet and two usb ports, but no hard disk (“no moving parts”!), no video card nor output, no input connectors for keyboard nor mouse. It has a low power ARM CPU and not much RAM, but it chugs along very happily under debian doing quite sophisticated things like Jeni’s adaptive Bayesian spam filtering. It’s a perfectly adequate file server for a LAN, or light loading from the net. Kudos++ to the guys and girls at http://www.cyrius.com/debian/nslu2/ and http://www.nslu2-linux.org/ for getting linux (and debian in particular) running on it, thus freeing it into a general purpose, low-power-consumption machine. I see this as a real win-win for the open-source/free-software movement and Linksys. I feel sure that nowadays more NSLU2s are sold to be “hacked” to run linux than are left running the supplied Linksys software. Linksys honoured their obligation under the GPL to release the source of the linux code they’d changed, thus enabling the hacking. Of course, being evil capitalists (!) they kept something: the ethernet driver (of all things) is still proprietary; but I for one can live with that even though it’s irksome. Congratulations all round. I’ve configured two slugs so far, and I hope to do more.