Niklas Leinz corusm

One liner for deleting images from a v2 docker registry

Just plug in your own values for registry and repo/image name.

registry='localhost:5000'
name='my-image'
curl -v -sSL -X DELETE "http://${registry}/v2/${name}/manifests/$(
    curl -sSL -I \
        -H "Accept: application/vnd.docker.distribution.manifest.v2+json" \

How to publish Python apps for human beings

So, you've created a Python app (be it a graphical user interface with Qt or the like, or a simple command line interface). Great! But how are others going to use it? Python applications often have dependencies (e.g. from third-party modules), and they also need a Python interpreter to run them. For a developer, installing all the necessary bits and bobs to make things work is okay, but that's unacceptable for a normal user - they just want to download the thing and run it.

Below are simple instructions to publish your app on the three main operating systems: Windows, macOS and Linux.

Docker compose as a systemd unit

Create file /etc/systemd/system/docker-compose@.service. SystemD calling binaries using an absolute path. In my case is prefixed by /usr/local/bin, you should use paths specific for your environment.

[Unit]
Description=%i service with docker compose
PartOf=docker.service
After=docker.service

How to mount a qcow2 disk image

This is a quick guide to mounting a qcow2 disk images on your host server. This is useful to reset passwords, edit files, or recover something without the virtual machine running.

Step 1 - Enable NBD on the Host

modprobe nbd max_part=8

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

	# Backup
	docker exec CONTAINER /usr/bin/mysqldump -u root --password=root DATABASE > backup.sql

	# Restore
	cat backup.sql \| docker exec -i CONTAINER /usr/bin/mysql -u root --password=root DATABASE


	# Install quemu, docker, etc
	yaourt -S qemu qemu-user-static binfmt-support

	# The quemu-user-static AUR package is outdated and broken. The .deb package they pull is no longer in the ubuntu repository.
	# Edit the PKGBUILD and use qemu-user-static_2.4+dfsg-3_amd64.deb (With SHA1 sum "84d83a16c60c82b6c579f2f750b04a3ac26c249b")

	# Enable ARM emulation
	update-binfmts --enable qemu-arm

	wget https://release.gitkraken.com/linux/gitkraken-amd64.deb
	sudo dpkg -i gitkraken-amd64.deb