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# Setup eduroam connection using personal certificate (802-1.x WPA EAP) 
# at the University of Passau.
#
# PREREQUISITES
#
# Instructions based on "Manuelle Einrichtung" [1] and Stackoverflow [2].
#
# 0) mkdir ~/.eduroam # create dir holding certificate files
# 1) download private key in PKCS#12 format [3], save as ~/.eduroam/eduroam.p12
# 2) download radius root certificate [4], save as ~/.eduroam/radius_rootcert.pem

sepastian

From: https://cromwell-intl.com/open-source/performance-tuning/file-systems.html.

Mount Parameters

Disable recording of access times when mounting the FS.

For example, find with access times enabled would upate the access time of every file found.

# /etc/fstab

sepastian

# Given an array of arrays s = [ [1,2,3], [4,5,6], ... ]
# compute the Cartesian product among the elements of s.

require 'pp'

s = [[1, 2], [3, 4, 5], [6, 7, 8, 9]]
pp s[1..-1].inject(s[0]){ |m,v| m = m.product(v).map(&:flatten) }
[[1, 3, 6],
 [1, 3, 7],
 [1, 3, 8],

sepastian

Install Win10 as a guest in QEMU, running on a Debian host.

# Host machine used.
uname -a
Linux x220 5.10.0-2-amd64 #1 SMP Debian 5.10.9-1 (2021-01-20) x86_64 GNU/Linux

This is based on https://linuxconfig.org/how-to-create-and-manage-kvm-virtual-machines-from-cli.

sepastian

# Oh-My-ZSH custom function to record left monitor from CLI.
# 
# Place in $ZSH/.oh-my-zsh/custom.
#
# Two monitors at screen 0, the left one connected at DP-1:
#
#     xrandr 
#     Screen 0: minimum 320 x 200, current 3840 x 1200, maximum 16384 x 16384
#     DP-1 connected primary 1920x1200+1920+0 (normal left inverted right x axis y axis) 518mm x 324mm
#       1920x1200     59.95*+

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# Place in $ZSH/.oh-my-zsh/custom.
#
# The following ZSH function uses GhostScript's `gs` command to reduce the file size of a PDF file.
# The result of compressing `test.pdf` will be written to `test.compressed.pdf`.
# If `test.compressed.pdf` exists, it will only be overwritten after confirmation.
#
# Now, restart/open a new shell and compress PDFs with:
#
#     compress_pdf test.pdf
#     File exists: test.compressed.pdf, overwrite (Y/n)? 

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# SSH into remote host "R", startup Jupyter on port XXXX.
ssh user@remotehost.com
jupyer notebook --no-browser --port=XXXX

# On the localhost "L", accessing jupyter via the browser:
# create a reverse tunnel, forwarding YYYY (L) to XXXX (R).
ssh -N -L YYYY:localhost:XXXX user@remotehost.com
          ---- --------- ----
            |       |      |
            |       |      ` port on remote where Jupyer is listening

sepastian

# Based on https://apple.stackexchange.com/a/389067/453491

# In order to calculate DPI, determine units and resolution first.
identify -verbose warc2corpus@2x_300dpi.png | grep -E -i "resolution|units"  
#  Resolution: 118.11x118.11
#  Units: PixelsPerCentimeter
#    png:pHYs: x_res=11811, y_res=11811, units=1

# 1 PixelsPerCentimeter corresponds to 2.54 DPI.
# Calculate DPI using the following command.

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class Heap
  def initialize(*elems)
    @h= heapify(elems)
  end
  def inspect
    return '(empty)' if @h.empty?
    @h
      .group_by.with_index{ Math.log2(_2+1).to_i }
      .map{ |l,vs| vs.join(' ') }
      .join("\n")

sepastian

Installing OpenWRT on a TP-Link MR3220 V2.2

Prerequisites

Download the latest TP-Link firmware

In case the original firmware needs to be restored. Firmware for the MR3220 V2.2 can be found here, select the most recent version (this guide uses TL-MR3220_V2_130423.zip):

http://www.tp-link.com/en/support/download/?model=TL-MR3220&version=V2