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Category: computers

Broken Time Machine

Published August 14, 2010

This is not good.

Danielle’s computer has been failing to back up properly to an AirPort-connected Time Machine volume, so with her volunteering at the 3-Day this weekend I figured I’d spend some time getting to the bottom of why.

First I thought the issue might be the questionable USB enclosure that the backup hard drive was in, so I swapped to another. No luck. Then I figured maybe the backup volume was corrupt, so I wiped that, but that didn’t help either; the backup still wouldn’t run. Next I thought that perhaps the local drive might be having issues, so I ran the Verify Disk function in Disk Utility, which promptly informed me that the volume was so damaged that I’d have to boot some install media and do an offline test. I did this, started the check, and received the message shown above informing me that the volume is so corrupt that it cannot be repaired. It will now not boot, sitting only at the Apple logo / spinning progress indicator screen.

This is not good.

Now I will have to back up all the accessible data by hand, and hopefully I’ll be able to get all of her music, documents, and photos along with config files needed to restore them. I’m hoping that this can be accomplished by hanging an FireWire disk off of the machine, installing OS X there, using Migration Assistant to pull data over, wipe (and test) the main drive, reinstall the OS there, then again migrate all data from the FW drive.

While it’s difficult to say what caused this, I strongly suspect it’s related to an alarm clock application that she’s been using for a while. This application will wake a Mac from sleep and sound an alarm. As her machine is a Macbook, which is not designed to run while closed (since they dissipate heat through the keyboard area), a program waking the machine from sleep while the machine is closed results in the machine immediately putting itself back to sleep. This would repeat over and over until the alarm was canceled or timed out. With this app in use for the last year or so, odds are good that this super-fast wake/sleep cycle has happened hundreds or thousands of times.

Due to the extremely complex things that happen when a machine is sleeping and waking, I strongly suspect that some things didn’t get read from or written to disk quite properly during the wake/sleep cycle and the disk became quite corrupt. Then, the software designed to repair this corruption couldn’t deal with how bad things were, left the disk in a less-usable state, and the machine is then left where it now is: failing to boot.

UPDATE: This corrupt disk problem was fixed as I hoped it would be above, with the external FW disk. Unfortunately Time Machine still isn’t working. Time to keep digging…

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Working Car!

Published June 8, 2010

This broken bolt is the reason for Sunday’s car failure. When it broke the serpentine belt tensioner came free, likely becoming lodged somewhere, and causing the car to cease working. Because the bolt broke off flush with the engine block and was in a particularly hard to reach place, the engine had to be lowered 2″, the bolt drilled, and then the bolt removed with an easy out / screw extractor.

As a result there was $187.54 in labor to fix the problem, with the bolt, new serpentine belt, and other misc parts only being $78.01. With the $100 for towing, this failure cost just under $400, which I guess isn’t too bad. It’s a bit frustrating that this comes only two weeks after paying my car off (early), but timing on this is really very random.

The guy at the shop (Shelby Tire) said they spent a while trying to figure out the cause of the broken bolt, but the AC compressor, power steering pump, and all other devices connected to the serpentine belt seemed fine, including the tensioner. The only cause he could figure was that the bolt was weak (or failing) and the AC kicked on just as the power steering kicked in, and the extra load on the belt snapped things. As I was turning a corner out of a parking lot having just turned the AC on when the problem happened, this makes sense. Hopefully it won’t happen again.

(This is also the first RAW photo that I’ve processed in the newly released / installed Adobe Photoshop Lightroom 3. One of its new features is markedly improved sharpening, and I must agree that it’s much better. After all, just check out those knurls on the screw head.)

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“100% New Compatible Toner Cartridge” for Xerox Phaser 6130 (Black)

Published May 21, 2010

After roughly 1.5 years of use the black toner cartridge in my Xerox Phaser 6130 finally ran out. Since the Xerox-branded cartridges cost somewhere around US$80 I decided to try this “compatible” cartridge from the venerable MonoPrice.com. While I’ve only used it for a few pages, it seems great so far. It fit nicely in the printer, the printer immediately recognized that K (black) was full, and the couple jobs sent to it have all processed smoothly.

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PC Engines alix2d13 and Netgate Enclosure

Published May 21, 2010

This week I received a PC Engines alix2d13 board and Netgate NET-CASE1C2REDU-ANT enclosure which will replace the venerable Trashwall. While Trashwall served its purpose for a while, I was getting tired of its noise (a slight but present hard disk whine) and power consumption and the need to manually set up utilization graphs and such.

After giving pfSense, a FreeBSD / pf-based firewall distribution which works nicely on embedded devices, a try I decided to move to it. I’ve now got pfSense v1.2.3 embedded (current stable release) installed on a 4GB SanDisk Ultra II compact flash card which the ALIX board boots to run the OS. Console output (when needed) is via serial port, but after the initial configuration, practically everything can be done via the web.

I’m running into a couple quirky problems with port forwards, but it’s otherwise doing a fine job of running my home network. DHCP with reservations, DNS, DynamicDNS (for DHCP clients to be resolvable), and NTP are all working as they should. Once I get the port forward issue sorted I’ll likely backup the config and give one of the pfSense v2.0 beta snapshots a go. If whatever beta snapshot happens to fail or doesn’t work out I can then just reimage the CF card back to v1.2.3 and reload the exported config. pfSense configs are simply XML files that can be backed up and restored at will, which is particularly convenient.

If you’d like to see more photos of my PC Engines alix2d13 setup, click here.

If you’d like to buy one, check out Netgate. The specific items I purchased for this are as follows, for a total of US$183.85:

· ALIX.2D3+B System Board: (3/1/256/LX800) with battery [ALIX.2D3+Battery]: US$140
· LIX.2D3 3 LAN Indoor Enclosure Red with USB & ANT [case1c2redu-ant]: US$24
· AC/DC 15V 1.25A 18W Switching Adapter only [PS-15V-1.25A-18W]: US$9.95
· SMA Dust Cap / Rubber Antenna Hole Plug [SMA Dust Cap Plug]: US$0.14/ea (2x)
· Postage via FedEx: US$9.62

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Google Maps Fails Again!

Published December 31, 2009

Here’s yet another failure of Google Maps in my area. Not only is my address not found (it worked just fine in the past but now has the street name listed incorrectly), my ZIP+4 alone doesn’t work, and now 22 Mile Rd. shows up improperly in Street View as 20 2 Mile Rd..

I just submitted the following bug report to Google about this:

Google Maps lists 22 Mile here properly, as the name '22 Mile Road'. When in Street View this is listed as '20 2 Mile', which is wrong.

We’ll see how far it goes. My last few bug reports, while acknowledged as correct and noted as being fixed in future releases, have resulted in only one fix that I can validate myself; more appropriate naming of roads on the GM Tech Center campus. It’s now been months since I reported my address as not working and it’s still not right. There are also problems where a local highway and surface road with similar names are sufficiently confused to make businesses appear along the wrong road. As can be seen here a bunch of locations are incorrectly placed roughly one mile east of their actual location. This too has been reported, and not fixed.

I currently use (and rather like) a T-Mobile G1 Android-based phone and I like it enough that I’m seriously considering buying a Nexus One when it launches. However, terribly inaccurate local data including not having my home address available limits some of the major selling points of the phone.

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Blue Light Special

Published December 14, 2009

Here’s a photo of my desk from a few minutes ago, after fitting a light behind the iMac. Taking a cue from home theater stuff where placing a dim light behind a TV provides nice ambient light and increases apparent contrast in the display, I fitted a 9W daylight colored compact fluorescent light† behind the display on a cheap clip-on light. This makes a nice glow behind the monitor and on the white ceiling which provides enough light for computer and peripherial use, but is dim enough to make for comfortable evening working. This light will eventually be switched using an X10 appliance switch, just as the normal desk lamp is, but these devices haven’t been received yet. Thanks to eBay they were cheap and should be here in a week or so.

Beneath the iMac you may notice the Millet Hybrid Maxed headphone amp which I built last year. It is connected to the AMB γ1 DAC which sits nicely on the Twelve South BackPack. Audio output for non-system sounds are switched from the main speakers to the DAC (and thus the headphones) as needed using Rogue Amoeba’s SoundSource. This works out well for when Danielle and I are both at our desks with audio playing, as respective use of headphones keeps us from driving each other insane. A few new cables are needed to sort out the connections without a rat’s nest, but these are on back order and likely won’t be here until the beginning of next year.

All in all, this is shaping up to be a nice workspace. The iMac is doing everything asked of it with gusto, the display is excellent, and the overall sound level in my office is down to profanely low levels. This is very nice.

† The lamp is a cheap Home Depot 5000K lamp with a rather poor CRI. It is not appropriate for photographic or color-critical work, but it’s just fine for room illumination, particularly indirect illumination bouncing off of a blue-painted wall.

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Twelve South BackPack

Published December 10, 2009

This is the Twelve South BackPack, a nice and simple metal stand for the back of an iMac or Cinema Display which clips (without marring) to the metal stand. It can then be used to hold external disks or whatever else, hidden behind the monitor.

Despite being a bit overpackaged and having fancier silkscreen that I’d expect on a small clamp-on shelf (both of which I suspect contribute quite a bit to the $29.99 price tag), it’s a nice little device. Assembly was pretty straight forward, requiring just a bit of adjustment to get it on the stand and centered. There are a series of plastic spacers which fit into the mounting clips, with different spacers needed for different types of iMacs or Cinema Displays, likely varying based on stand thickness and angle. A fixed screw protruding from the clip and its hexagonal base fit into slots on the metal shelf itself. The clips are then fit around the sides of the stand, and its weight holds it securely in place on the stand.

While some of the photos that I took show it with a hard drive, I suspect that it’ll see most use from me holding the AMB γ1 DAC tucked nicely out of sight, driving some manner of headphone amp. For now this will probably be a Millett Hybrid Maxed, but I’m considering building another headphone amp over the winter. Perhaps the AMB M³ with its active ground would work out well…

More photos of the Twelve South BackPack are available here, if you’re interested: Twelve South BackPack

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Time Machine for… FreeBSD?

Published December 6, 2009

This week I finally got around to writing a new backup script for my webserver. I have it automatically pushing backups to a device at home, but in the past I’d only been doing a nightly rsync with --delete and periodic offline backups. The problem with this was that should something happen to my server and cause a data loss, but not be noticed before the next backup ran, the current backup would be modified reflect the now-compromised data, potentially causing massive data loss. Clearly this was a bad thing, and something had to be done.

A new backup scheme was devised and now that the new scripts are tweaked I wanted to present them here. rsync is still being used, but thanks to its glorious --link-dest option which makes hard links as it can, files already stored on disk (say, from a previous version of the backup) are reused, saving space. This is how Apple's Time Machine works, just without the nice GUI. The result is that I have a series of directories starting with backup.0 up through potentially backup.30 on the target, each containing a different backup. The suffixed number represents how many versions old the backup is. These versions are generally created once per day, but on days where the backup does not complete successfully the version is not incremented.

To start, there is a script called dailybackup.sh which runs once per day on banstyle.nuxx.net. This script pushes a backup to a Mac at home as follows:

  1. If needed, remotely execute rotatebackup.sh on the backup server. This will move backup.0 to backup.1, backup.1 to backup.2, keeping no more than 30 backups. The need to rotate backups is determined by the presence of backup.0/backup_complete. If there is no backup_complete file we know that the previous backup was not successful and that we should reuse backup.0.
  2. Create a new backup.0 and populate it with a backup_started flag file.
  3. Run the backup job via rsync.
  4. If the job completes successfully (exits with something other than 0 or 24), continue. Exit code 24 indicates that some files disappeared during backup, and as mail files (amongst others) tend to move and be deleted by users during the backup job, this is not a critical error for us.
  5. Remove backup_started and create the backup_complete flag.

Copies of the aforementioned scripts can be found here, if you’d like to look at / use them: dailybackup.sh · rotatebackups.sh

These scripts assume the presence of backup.0, a full copy of your backup, which you’ll have to create yourself before use. There’s also likely some necessary changes for your environment, most likely in some of the variables set at the top of the scripts, such as the number of days for which to keep backups and logs, the target hostname, SSH port, username, etc.

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SyncForegroundPolicy precludes ReportDC and ReportControllerMissing

Published December 2, 2009

In troubleshooting some Group Policy processing issues I attempted to set ReportDC(1) and ReportControllerMissing(2) to notify me, upon login, that a Windows machine was using Cached Credentials(3). After a brief period of confusion I found that turning off (or setting to 0) SyncForegroundPolicy, the registry key which holds the policy setting Always wait for the network at computer startup and logon, will preclude this the aforementioned notification. Thus when receiving the policy-based setting disabling SyncForegroundPolicy to ensure that the machine starts faster by not waiting for the network to come up before beginning policy processing, the diagnostic popup indicating the use of cached credentials does not work.

Note that the steps for setting the ReportDC and ReportControllerMissing values can be found in 242536 – User is not alerted when logging on with domain cached credentials.

(1) HKU\.DEFAULT\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\ReportDC, set to 1 (the default) to display the domain controller message.
(2) HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\ReportControllerMissing, set to TRUE to display the message.
(3) HKLM\Software\Policies\Microsoft\Windows NT\CurrentVersion\Winlogon\SyncForegroundPolicy, set to 1 for enabled / wait for network. The opposite setting of 0 is disabled / don’t wait for network.

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