The Treehouse Blog

Doug‘s recent gift of some 1-wire temperature sensors set me on the path to some more in-depth home monitoring.  The extent of home monitoring to this point had been the use of two relatively ancient AP9605 ^(ad) boards for the SmartUPSes ^(ad) in my network closet and office.  This combination provides SNMP-able power load and temperature readings that I graph using NetMRG.

Another home improvement project I have recently completed is having a water softener/conditioner installed.  This system has a built-in water meter, which just begs to be monitored.  While reading about home monitoring projects in general, I had read that some power meters output IR pulses that count energy usage.  I used my digital camera after dark to confirm that my meter does indeed appear to do this.  Between these two items, I clearly had a use for two counters.  The other monitoring goal I had was temperature and humidity information for my crawlspace.  The bottom of the insulation in my crawlspace seems to get wet in the summer from condensation, and I’d like to keep tabs on it.

The core of this project involves having a 1-wire network.  For the PC interface, I elected to get a LinkUSBi from iButtonLink.  I opted for the “scratch and dent” model to save a few bucks, and I have not even noticed any real cosmetic issues with it.  I setup the OWFS software on my firewall by recompiling Doug’s SRPM for EL6.  I’m using a phone distribution block ^(ad) to connect the multiple 1-wire devices back to the LinkUSBi.  The one gotcha I’ve noticed with this is that the 1-wire interface requires the correct polarity and the majority of RJ11/RJ12 phone patch cables are rollovers – they swap pins.  When a 1-wire device is connected with reversed polarity to the network, the LED on the LinkUSBi stays lit constantly and no devices can communicate.

The crawlspace temperature/humidity sensor I selected was the MS-TH from iButtonLink.  At $64 it seemed overly expensive, but with pricing other options including kits, it still appears to be the best value for a 1-wire humidity sensor.  I installed it on the beam in the crawlspace and ran a new CAT5e run to it from the network closet, patched into the 1-wire bus.  I wrote a script to strip the leading spaces that OWFS provides (WHY?) and graphed the sensors in NetMRG.

In the upcoming part 2, I’ll discuss the details of the 1-wire counter setup to provide power and water metering.

The desktop upgrade from Fedora 15 to Fedora 16 was about on par with the upgrade from 14 to 15.  Instead of the disaster that is Gnome 3, we’re instead greeted with GRUB 2 and new systemd quirks.

The main portion of the upgrade itself went smoothly.  No unexpected surprises from anaconda until the notice that the bootloader didn’t install right.

GRUB 2

So apparently Fedora 16 incorporates GRUB 2.  While its error messages seem far friendlier than GRUB classic, I really did not delve into all of its supposed benefits.  One downside is that when built with RAID support (which I seem to need since my /boot partition is mirrored), the core.img file ends up >32KiB, and thus does not fit in the post-MBR gap present on my drives.

To address this, I used a gparted live CD and resized and moved the first partition of each drive (which happen to be NTFS drives for my Windows 7 install, one of which was the system volume).  This provided a 2MiB gap between the MBR and first partition.  Booting back into the Fedora 16 rescue mode and using grub2-install on both drives successfully installed GRUB2 and, following a reboot, allowed Fedora 16 to load.

Unfortunately, these partition table and file system hijinks left Windows 7 with a bit of a problem, seeing as it would not boot.  The recommended method of using the Windows 7 installer’s “Startup Repair” feature was unsuccessful.  The “bootrec /fixboot” would not fix it, giving an “unsupported filesystem” error.  Using diskpart to set the Windows partition to active appears to resolve this, and the fixboot succeeds.  Naturally, I ran fixmbr at some point, which wiped out GRUB again, and thus it had to be reinstalled.  Success with booting both Windows 7 and Fedora 16 was then achieved.

NFS mount

The machine has one NFS share mounted via /etc/fstab.  After the upgrade, this would fail to mount during boot, but would have no difficulty being manually mounted after boot.  After researching a variety of wrong paths with various systemctl changes, the one I found to resolve this was “systemctl enable NetworkManager-wait-online.service”.

Update 1/8:

The upgrade of my HTPC wasn’t too painful.  Mucked with partitions to make room for GRUB2 ahead of time, had to change my lirc init script to not confuse systemd, disable screensaver in gnome 3 (yes, shouldn’t be using gnome to run mythtv – need to add that to the list), re-enabling services that weren’t automatically figured out from existing init scripts, switched mounts from /dev/md* to UUID-based to get the ordering right in the new boot sequence, mythtv ownership changes, etc, etc.

A while back I had to diagram interactions between components in a KRB5+LDAP+NFS4 system.  Instead of laying this out by hand, I went with GraphViz.  I think I had known of its existence, but when I forget what the name of it is, I tend to look up this diagram of Ender stories from Wikipedia.  The diagram I made is below, if you happen to have a Celerra laying around.  Recently, I’ve started playing with GraphViz again to do some stuff for my current job, but have found out that one thing it doesn’t really do are the directory-tree type layouts one expects to find in most file managers today.  Maybe they’ll add that as a different layout engine at some point.