Unsorted Notes

SSH server on Ubuntu 18.04 (desktop)



sudo apt install tasksel
sudo tasksel install openssh-server

Python OpenCV


basic server install: pip install opencv-python-headless
basic desktop install: pip install opencv-python

OpenCV image to PIL image conversions:

from here:

import cv2
import numpy as np
from PIL import Image

img = cv2.imread("path/to/img.png")

# You may need to convert the color.
img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
im_pil = Image.fromarray(img)

# For reversing the operation:
im_np = np.asarray(im_pil)

pip version problem

Annoying “ImportError: cannot import name ‘main'” after upgrading to pip 10.
Rollback via:

python3 -m pip install –user –upgrade pip==9.0.3

Update WordPress from command line:

wp core check-update
wp core update
wp plugin list
wp plugin update wp theme list
wp theme update

Key/Value Databases

  • Ardb – A Redis API compatible database but supporting disk based access (i.e data does not have to be in RAM). As the persistence backend technology, it supports many database engines, like Google’s LevelDB, Facebook’s RocksDB, OpenLDAP’s LMDB, WiredTiger (more info on link). Written in c++
  • ledisDB – Similar to above, written in Go, impressive benchmarks
  • CockroachDB – scalable, transactional, geo-replicated data store (GitHub)
  • cuttdb – hash based key value database for persistent storing massive small records – small memory footprint, scalable to massive datasets.

  • Javascript Charting Libraries – good comparison from Wikipedia

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