Łukasz Wieczorek's blog A slice of programmer's life

Random findings

04 May 2017

Secure GPG key generation using gpg:

gpg2 --gen-key
gpg2 --list-keys
gpg2 -K --keyid-format long --with-colons --with-fingerprint
gpg2 --export -a $ID

Other useful GPG commands;

gpg2 --delete-secret-key $email
gpg2 --delete-key $email
gpg --armor --export $email > "${email}.asc"

Long ssh key generation using ssh-keygen:

ssh-keygen -b 16384

Setting fedora docker directories permission using chcon:

sudo chcon -Rt svirt_sandbox_file_t /var/lib/docker/volumes/
chcon -Rt svirt_sandbox_file_t $volume_dir

Burning Ubuntu to USB using dd:

lsblk -f
umount /dev/sdb1
dd if=ubuntu-16.04.2-desktop-amd64.iso of=/dev/sdb bs=4M status=progress
sync

Ignoring changes for file in git:

git update-index --(no-)assume-unchanged

Removing project containers using docker-compse:

docker-compose down --rmi all --remove-orphans

Rebuilding project containers using docker-compose:

docker-compose up --build

Updating all globally installed gems using gem and cut:

sudo gem update `gem list | cut -d ' ' -f 1`

Upgrading to Fedora 26 using system-upgrade:

dnf upgrade --refresh
dnf install --assumeyes dnf-plugin-system-upgrade
dnf system-upgrade download --refresh --releasever=26
dnf system-upgrade reboot

uWSGI maximum scoket connections

12 Oct 2016

Were you ever wondering why are you getting HTTP 502 responses from your uWSGI on high connection count?

Setting net.core.somaxconn might help.

Temporarily:

$ cat /proc/sys/net/core/somaxconn
# echo 4096 > /proc/sys/net/core/somaxconn

Temporarily with sysctl:

# sysctl -w net.core.somaxconn=1024

# echo 'net.core.somaxconn=1024' >> /etc/sysctl.conf

Reload kernel parameters after changes:

# sysctl -p

Change uWSGI settings for vassal:

cat /etc/uwsgi/vassals/vassal.ini
echo 'listen = 1024' >> /etc/uwsgi/vassals/vassal.ini

Restart uwsgi:

service uwsgi restart

Debugging Django code

12 Oct 2016

Ever tried debugging Django code in the CLI offered by manage.py shell or shell_plus?

It gets nasty when you need to write more than few lines of code to run something.

Here’s what you can do instead:

import os

import django


os.environ['DJANGO_SETTINGS_MODULE'] = 'project.settings'
django.setup()


def main():
    print 'Hello world!'


if __name__ == '__main__':
    main()