Saturday, December 5, 2015

make-bcache: Device or resource busy

When setting up bcache, I ended up being halfway there. Bcache could not be set up, because it's not a blank block device.

sudo make-bcache -C /dev/sda3 -B /dev/sdb1 --wipe-bcacheDevice /dev/sda3 already has a non-bcache superblock, remove it using wipefs and wipefs -a

Wiping up the partition would not work as bcache is already using it for something

sudo wipefs -a /dev/sda3
wipefs: error: /dev/sda3: probing initialization failed: Device or resource busy

Also detaching the device from bcache won't work, since the bcache0 is not really there yet.

echo eb99feda-fac7-43dc-b89d-18765e9febb6 > /sys/block/bcache0/bcache/detach
cd /sys/block/bcache0 bash: cd: /sys/block/bcache0: No such file or directory
Seems the solution was to stop the bcache instead:

cd /sys/fs/bcache/eb99feda-fac7-43dc-b89d-18765e9febb6
sudo sh -c "echo 1 > stop"

Wednesday, November 18, 2015

Creating a Debian repository

I wanted to automate setting up my custom application on multiple Raspberry PI's. It was time to learn how to set up a Debian repository.

On my personal web server, the steps to create the repository:

cd /var/www
mkdir debian
cp /path/to/my-package_0.0-1_armhf.deb debian/
dpkg-scanpackages debian /dev/null | gzip -9c >debian/Packages.gz

On each Raspberry:

sudo sh -c "echo 'deb debian/' > /etc/apt/sources.list.d/myserver.list"
aptitude update
aptitude install my-package

Helpful, almost complete instructions I found at and

Sunday, May 3, 2015

OpenVPN IP packet with unknown IP version=15

I ran into this error when setting up Viscosity OpenVPN client for my Mac.

   IP packet with unknown IP version=15 seen
My router at home is running OpenWrt. I knew it has a good OpenVPN setup as I have been successfully connecting using OpenVPN for Android.

The key to getting the Viscosity to work with OpenWRT was selecting LZO compression: "Not specified" under preferences / options.

Thursday, April 30, 2015

Mac OS X lock screen immediately

The one thing nice about Windows is being able to lock screen quickly when you leave your desk by pressing Windows-L.

I have been wondering how to do this with my Mac. Now that I finally bothered to actually google for it for a while, this is the best I found so far:

open /Applications/Utilities/Keychain\
This adds a lock icon in the menu bar. It's not quite as convenient as Win-L, but does the trick.

From donmontalvo at

Sunday, February 15, 2015

Canon CP910 - Connection Method not supported -9786 on OS X Snow Leopard

I've been very happy with the Canon Selphy CP910 photo printer. Print quality is excellent and it has been very easy to use. Except with my oldest Mac, which is stuck on Snow Leopard 10.6.8.

Drivers install fine. Printer is found and installed. But always when trying to print, the dreaded error message comes up:

Connection Method not supported -9786

Apple forums have all kinds of voodoo to make it work, none of it helps. The key to success is:
  • In "Add printer" dialog, WAIT, do nothing, for ~10 seconds.
  • Additional, working CP910 appears with the magic word 'cnybmscp'.
Do not install the "Bonjour" CP910. It's a trap. It will fail you.
Do install the "cnybmscp" CP910.