Things I learned last week (1)

Android emulator

There was a lot of progress made on the Android emulator since the last time I used it for development; sensors can now be emulated, the display can use the GPU of the host and most important, the emulator can use the virtualization support of the host to run an x86 image at close to native speed. The GPU support and virtualization are now more or less mandatory because of the size of the display of modern Android devices, so it is worth the effort to configure Android for this. That requires a computer that can run KVM and to install the x86 system images.

The command line to start the emulation looks like this:

$ emulator -avd avd_name -gpu on -qemu -m 512 -enable-kvm

Unfortunately when the AVD is new, the window displayed stays black. The solution is to run it the first time with kvm disabled:

$ emulator -avd avd_name -gpu on -qemu -m 512 -disable-kvm

After this, the first command line above can be used.

CPU heatsink

My desktop computer is dying, so it is time to build a new one. I replaced the Asus K8N-DL by a KCMA-D8 motherboard and ordered the CPUs and memory to build it last week-end. Unfortunately I did not planned that the CPUs would arrive without heatsink, and unfortunately heatsinks for C32 socket are not available in stores. I suppose it makes sense that the CPUs comes without heatsink as these kind of motherboard can be used in 1U chassis, which requires a very different type of heatsink than in a tower. But now I have to wait until I receive the heatsink to finish the build.

Rescue USB flash drive

I run Debian Sid on all my non-server computers, which means that from time to time there is something to repair after an apt-get upgrade – that’s not as insane as it seems as upgrading a computer each day with the latest packages and fixing whatever broke is a great way to learn stuff. After all I am a computer professional, not a museum curator.
To repair the most broken installation I keep a Debian Live distribution on a flash drive. On the other hand my desktop computer also use a flash drive to boot GRUB (this machine uses a RAID10 array, which cannot be used for booting), so for this new build I decided to put the Debian Live distribution on the same flash drive, so I do not have to search the rescue flash drive next time I break something. It took me a while, but here the process:

Download a recent Debian Live ISO file, mount it on a loop and copy the content of the live directory on the flash drive:

# mount -o loop Downloads/debian-live-7.0.0-amd64-rescue.iso /mnt
# mkdir /boot/live
# cp /mnt/live/* /boot/live/
# umount /mnt

Then add the following in /etc/grub.d/40_custom:

menuentry "Debian rescue" {
    echo 'Loading Debian rescue ...'
    linux /live/vmlinuz boot=live live-config live-media-path=/live
    echo 'Loading initial ramdisk ...'
    initrd /live/initrd.img
}

Then update grub.cfg with the following command:

# update-grub

Note that in this configuration the flash drive is mounted on /boot.

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