Raw Matter - Debian

Execute stuff from dhcpd.conf

nospam@example.com (Adrian von Bidder) — Sat, 29 Jan 2011 16:58:57 +0100

Since my NAS at home also acts as DHCP server, the obvious idea was to back up my PC and my laptop whenever they're switched on. Sadly, the documentation on how to do this from dhcpd.conf (instead of watching log files and reacting to log messages) is quite hidden, so here it is: I found the "execute" keyword (see the dhcp-eval manpage), and I found Tim Gustafson, which allowed me to pull it off (although, since I only have the two computers, I opted for a execute statement each and hardcoded the client IP in the call to the backup script. So I don't know if the address parsing stuff he does is correct.)

So the host statements for me look just like this:

  host laeggerli-wifi {
    hardware ethernet 00:22:69:aa:bb:cc;
    fixed-address 172.23.5.19;
    on commit {
      execute("/usr/local/sbin/dhcp-run-backup", "commit", "laeggerli");
    }
  }

And the script to start dirvish is similarly simple, except that it needs to fork to the background to make sure dhcpd is not blocked. The sleep 600 is based on the theory that if I'm on my way out in the morning and need to check mail quickly, that will be less than 10 min, whereas when I'm still online after 10 min, there's a good chance that the back up will go through. Obviously, this could be improved...

#! /bin/bash

# called by dhcpd.conf
# arguments:
#  $1 -> "commit" if called from dhcpd.conf, fork into background
#     -> "run"    if called internall from first instance
#  $2 -> client host

if [ "$1" == "commit" ]; then
    # fork to background
    $0 run "$2" >> /var/log/dhcpbackup.log 2>&1 &
    exit 0
fi

if [ "$1" != "run" ]; then
    echo error
    exit 1
fi

# figure out which host:

host="$2"
if [ "$host" != "laeggerli" -a "$host" != "faehrimaa" ]; then
    echo "Unknown host: $2"
    exit 1
fi

# did backup already run today?
d=`date +%Y%m%d`

if [ -d "/srv/backup/${host}_home/$d" ]; then
    exit 0
fi

# wait 10min before actually running the backup
# (if computer still runs after 10min, it'll likely run for longer...

sleep 600
ping -n -w 3 $host >/dev/null 2>&1 || exit 0

agentpid="/var/run/dirvish/ssh-agent-$host.pid"
[ -f "$agentpid" ] && \
    kill $(< "$agentpid") 2>/dev/null
mkdir /var/run/dirvish >/dev/null 2>&1
eval `ssh-agent` >/dev/null 2>&1
echo $SSH_AGENT_PID > "$agentpid"
ssh-add /etc/dirvish/ssh-key >/dev/null 2>&1

/usr/sbin/dirvish --vault ${host}_home
/usr/sbin/dirvish --vault ${host}_root

/usr/sbin/dirvish-expire --quiet --vault ${host}_home
/usr/sbin/dirvish-expire --quiet --vault ${host}_root

kill $SSH_AGENT_PID
rm "$agentpid"

(I don't claim any rights on any of it, it's trivial enough.)

Cyrus

nospam@example.com (Adrian von Bidder) — Tue, 04 Jan 2011 17:14:24 +0100

Just say no.

Filed under “Debian” since this is a Univention system which is based on Debian (still etch, though.) And what specifically annoyed me was today

That the mailbox list and the actual on disk files can get out of sync.
That this causes nice “System I/O error: %m” messages (the %m part is verbatim. Nice, isn't it?) in cyrquota, and similar messages in cyradm for “sam” commands.
That, while this can be fixed with a cyrrecover on the mailbox (a recursive recover on the parent doesn't bring back the mailbox, so I need to call cyrrecover on each affected mailbox separately), the output of cyrquota displays the mailbox as “domain!mailbox^name.folder” while cyrrecover expects “mailbox.name/folder@domain”
That the System I/O error causes cyrquota to stop, so I need to sit here and restart it countless times. (At least it seems to pick up where it stopped, so I don't have to wait that long until it comes to the next problem.)

I knew from other experiences that one shouldn't use cyrus, but it can't be said often enough... And since I usually don't use it, it amazes me anew every time I have to babysit an installation. While I don't have a similarly big installation to compare it, I've found Dovecot to be very nice. Admittedly it doesn't have that many features.

Order Your Debian Swirl Umbrella Now

nospam@example.com (Adrian von Bidder) — Sun, 12 Dec 2010 13:30:00 +0100

Ok, here we go: It seems that I'll receive the umbrella (big picture) in the first week of June, so I'm taking orders now. Please read this posting carefully if you want a Debian umbrella.

Update IV 2010-12-12: Orders are now processed via debian.ch, so just go over there for your Umbrella. I still have a very few umbrellas here in Basel, so if you want to pick one up locally you're still welcome.

About CHF 5 to 6 per umbrella will go to debian.ch (where it is held as official Debian money under the authority of the DPL.)

(Old version of this article removed. You're still welcome to send money to my bank account, but you won't get an umbrella in return.)

Tool: incron

nospam@example.com (Adrian von Bidder) — Sat, 20 Nov 2010 08:39:21 +0100

One in the “obvious, now that you mention it” category. The package description is good enough:

incron is an "inotify cron" system. It works like the regular cron but is driven by filesystem events instead of time events. This package provides two programs, a daemon called "incrond" (analogous to crond) and a table manipulator "incrontab" (like "crontab").

Where “filesystem events” is anything that is reported by inotify; see the inotify(7) manpage. I didn't test and/or use it since I stumbled on it while searching for something completely different, but it sure sounds useful. The important feature not mentioned in the package description: can it limit how often an event triggers a script execution? Reading the manpage, it doesn't appear so, but there's IN_NO_LOOP to “... disable monitoring events until the current one is completely handled (until its child process exits).” Which obviously opens up all kinds of race conditions. So I guess this tool needs to be used with care. Still, I guess a good candidate is monitoring /etc/aliases to run newaliases on change.

Debian Umbrella Arrived Today

nospam@example.com (Adrian von Bidder) — Tue, 15 Jun 2010 19:30:52 +0200

Update 20100618: Added Debconf info.

The famous Debian Umbrellas (big picture) have finally arrived, so I'm keen to get rid of them. Order yours now!

Information about Debconf: I'm not coming to Debconf. But Luca Capello was friendly enough to offer to carry some umbrellas. Coordination via the wiki, orders need to be placed before June 27th.

New Employer

nospam@example.com (Adrian von Bidder) — Thu, 03 Jun 2010 22:16:53 +0200

The joys of a new employer ... only 5min by bike to the office instead of 1h by train. And, of course, we're using Debian a lot, and I may do the odd bit of Debian work on company time. Like, right now, working with Klaus Zerwes on getting JWhoisServer uploaded. I hope more opportunities come up.

The Debian Umbrella: Soon.

nospam@example.com (Adrian von Bidder) — Wed, 26 May 2010 20:44:31 +0200

Update: I'm taking orders now.

I was planning to take orders for the Debian Swirl umbrella starting tonight, but a bit of research showed that shipping prices for parcels are insane (CHF 37 for europe), but it seems I can get away with sending this as a Swiss Post “Maxi Letter” instead, which would result in a shipping price of CHF 12.50 for four and CHF 24 for up to eight umbrellas (1kg or 2kg.) So now I'll go and look into getting some kind of flattish box to stay within the allowed dimensions before I can be sure this is possible. In any case, I expect the delivery in the first week of June.

Since I'll not be coming to Debconf, it would be nice if somebody could take some umbrellas to New York. I'm currently not travelling much, so I'd have to rely on a friendly volunteer. (I'm based in Basel, Switzerland; I am known to go to Zürich regularly.)

Yay! Debian Logo!

nospam@example.com (Adrian von Bidder) — Wed, 14 Apr 2010 19:02:08 +0200

Conditions for ordering: Not yet. The umbrella will be available ca. end of May, I'll give details about ordering it then. Information so far: CHF 25 per umbrella (ca. EUR 17 / USD 23), including ca. CHF 6 donation to Debian (via debian.ch); at least at first, I plan to ship in lots of 5 or more to save postage. International travellers should coordinate... (if you're close to Basel, Switzerland, you will obviously be able to get one directly as well.)

Update 2010-06-15: I got the umbrellas now, so you can order them.