LVM, mdadm, and partitioning.

This is a mind-dump after an excruciatingly mind-numbing week.

Somehow, with a FreeDOS installer USB I managed to accidentally corrupt the LVM data on my RAID array. This thing has files on it that go as far back as 1994*, so I was reasonably upset about the loss. Fortunately the situation was resolved, but I wanted to leave some notes for the next time I have completely forgotten how LVM works with mdadm.

First, disks used in the mdadm array do not need a partition table. I remembered this and didn’t mess with the (functioning) raid array.

Second, LVM does not need a partition table when it is using an entire device. I forgot this, and went directly to “trying to restore a corrupted partition” instead of “trying to restore last-known-good LVM data as found in /etc/lvm/archive/”.

Using testdisk, gpart, etc is a BAD IDEA if your disk never had a partition to begin with. These tools will recognize that you have a file system on the disk, but they can’t figure out that it was an LVM-only construct. The result will be an unmountable, mis-sized, “partition does not start on a sector boundary” mess. As you can see from the answer to the question I posted on SuperUser, I actually had to zap the partitions I tried to create to be able to move forward.

Note: fdisk is for MBR, <2TB disks. parted is for GPT, >2TB disks.

* Even I am surprised by this! Apparently it is a Palm Pilot archive… that can probably be deleted, huh?

A Better Python strftime / strptime Table

I present two tables that reformat the Python strptime, strftime documentation. The first is a short table with the most useful directives, the second is a longer table with all of the directives. This is easier for me to scan than the native docs. Hopefully it will help others as well.

YEAR%Y4-digit1970, 1988, 2001, 2013
MONTH%mDecimal zero-padded01, 02, ..., 12
DAY%dDecimal zero-padded01, 02, ..., 31
HOUR%H24-hour clock, zero-padded00, 01, ..., 23
MINUTE%MDecimal zero-padded00, 01, ..., 59
SECOND%SDecimal zero-padded00, 01, ..., 59
TIMEZONE%zUTC offset(empty), +0000, -0400, +1030
ISO format%Y-%m-%dT%H:%M:%S%z

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Good Old Disk Utility

If you have been sadly struggling with the new Apple Disk Utility software, I can confirm the instructions on this page work to restore the old Disk Utility. I can make no claims as to the reliability of running the old Disk Utility on El Cap, however.

speedtest-easy released!

Want to see if your ISP is providing the service they promised and don’t care about “scientific methodology?” Use speedtest-easy!
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“Personal is not the same as important.”

This juxtaposition of two news stories struck me today:

Upgraded LIGO detectors spot gravitational waves.

With Quartz’s App, You Don’t Read the News. You Chat With It.

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I did not invent Bitcoin

Despite LinkedIn’s recent claims, I am not the inventor of Bitcoin.  Continue reading

Replacing drives with mdadm

Simple, but very helpful.

SATA hotswap drive in mdadm RAID array.

I usually am just swapping out failed drives, which is pretty simple when you are running a spare. However, to increase the size of the array I need to swap out otherwise healthy, running drives. An easy but nerve-wracking procedure.

Twitter Embedded Timelines on self-hosted WordPress

Quick tip for hosting Twitter embedded timelines on a self-hosted WordPress. You will need a mere two links:

The Jetpack plugin brings an array of cool features to self-hosted that was previous only available via It was non-obvious why I could not simply follow the instructions in the guide, and searching the plugins for “Twitter Timeline” does not bring up much useful information.

Enjoy your new embedded Twitter timeline!

Remote linux-based Time Machine using netatalk instead of smb

Update 2015-12-12: The info in this post is no longer correct; you can now simply follow the instructions on this thread, particularly this post on Dae’s blog to get Time Machine up-and-running. 😄

If you previously followed my instructions, to back out of the home-built netatalk, you can try the following:

sudo apt-get remove netatalk
cd /usr/local/src/netatalk
make uninstall

Then follow the instructions posted above.

My large file server once was able to act as a Time Machine provider over-the-air, back before Apple disabled the ability to use Samba shares as Time Machine disks. However, following a few simple instructions from these helpful folks below, I was able to make OTA Time Machine backups happen again.

Thanks, Daniel and Pepijn!

VMware Fusion Networking Tips and Tricks


VMware Fusion’s networking configuration is a bit obscure and it is difficult to find information about it on the ‘net. I usually only need to achieve the following bits of config change, and they really only serve my need to tightly control all the things. I am posting this information here so that I never forget again.

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