cd ~/.rbenv/plugins/ruby-build
git pull

cd ~/.rbenv
git pull

rbenv install --list

rbenv install 2.5.3
rbenv global 2.5.3

gem install bundler

$ journalctl -xf -u mastodon-*

$ systemctl start mastodon-*.service

$ systemctl stop mastodon-*.service

$ systemctl status mastodon-*.service

$ RAILS_ENV=production bundle exec rails c

$ sudo su - mastodon

$ psql

=> \l

=> \q

sudo -u postgres pg_dump mastodon_production > mastodon_production.sql

rvm get latest

git checkout upstream/master Gemfile.lock
git checkout upstream/master db/schema.rb

git pull
cd .. && cd -

gem install bundler
RAILS_ENV=production bin/bundle; bin/bundle clean

RAILS_ENV=production bin/rake db:migrate

RAILS_ENV=production bin/rake assets:precompile 
RAILS_ENV=production bin/rake assets:clean

bin/eye restart web 
bin/eye restart sidekiq

fuser -kim /dev/sdd1

umount /dev/sdd1

It's about meaning not money

$ brew install redis

$ redis-server /usr/local/etc/redis.conf

$ cat /usr/local/etc/redis.conf

$ redis-cli ping

$ git tag -l

$ git checkout $(git tag -l | grep -v 'rc[0-9]*$' | sort -V | tail -n 1)

Traction Thinking

Spend 50% of your time on product and 50% on traction.

• get feedback from early customers
• what features are missing
• which part of the experience are broken

pip list

pip install package_name

pip install --user --upgrade matplotlib

scp <source> <destination>

scp /path/to/file username@a:/path/to/destination

scp username@b:/path/to/file /path/to/destination

vi .bundle/config

BUNDLE_FROZEN: "false"

$ sysctl -n hw.physicalcpu

$ sysctl -n hw.logicalcpu

$ brew install redis

$ brew services start redis

$ redis-cli ping

OS X Screencast to animated GIF

• Open "Quicktime Player",
• Go to File -> New Screen Recording
• Selected screen portion by dragging a rectangle, recorded 13 second video.
• Go to File -> Export -> As Movie
  • Saved the video in full quality with the filename in.mov

ffmpeg -i in.mov -s 600x400 -pix_fmt rgb24 -r 10 -f gif - | gifsicle --optimize=3 --delay=3 > out.gif

• -r 10 tells ffmpeg to reduce the frame rate from 25 fps to 10
• -s 600x400 tells ffmpeg the max-width and max-height
• --delay=3 tells gifsicle to delay 30ms between each gif
• --optimize=3 requests that gifsicle use the slowest/most file-size optimization

• ffmpeg to process the video file
• gifsicle to create and optimize the an animated gif

brew install ffmpeg 
brew cask install x-quartz #dependency for gif...

Let's encrypt a 100 MB file using the latest browser - WebCrypto API Speed Test 

25 MB -> 3.0 seconds
50 MB -> 5.8 seconds
100 MB -> 14.2 seconds

25 MB -> 4.2 seconds
50 MB -> 7.3 seconds
100 MB -> timeout

25 MB -> 10.0 seconds
50 MB -> 19.1 seconds
100 MB -> timeout

rvm use 2.3.3@appname --create

rvm --create --ruby-version 2.3.3@appname

> CREATE USER 'username'@'localhost' IDENTIFIED BY 'password';

> CREATE DATABASE IF NOT EXISTS db_name;

> GRANT ALL PRIVILEGES ON db_name.* TO 'username'@'localhost' IDENTIFIED BY 'password';

• mysql2 0.4.x works with Rails / Active Record 4.2.5 - 5.0 and higher.
• mysql2 0.3.x works with Rails / Active Record 3.1, 3.2, 4.x, 5.0.
• mysql2 0.2.x works with Rails / Active Record 2.3 - 3.0.

> var pubkey = "-----BEGIN PGP PUBLIC KEY BLOCK----- ... "
> openpgp.key.readArmored(pubkey)

> openpgp.key.readArmored(pubkey).keys

> openpgp.key.readArmored(pubkey).keys[0].getExpirationTime()

> openpgp.key.readArmored(pubkey).keys[0].subKeys

> openpgp.key.readArmored(pubkey).keys[0].subKeys[0].getExpirationTime()

> openpgp.key.readArmored(pubkey).keys[0].verifyPrimaryKey()

> openpgp.key.readArmored(pubkey).keys[0].subKeys[0].verify(openpgp.key.readArmored(pubkey).keys[0].primaryKey)

> openpgp.enums.keyStatus

iptables -L

/etc/iptables.test.rules

iptables-restore < /etc/iptables.test.rules

iptables -L

iptables-save > /etc/iptables.up.rules

iptables -A INPUT -s IP-ADDRESS -j DROP

ALTER DATABASE database_name CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;

ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

ALTER TABLE table_name CHANGE column_name column_name VARCHAR(191) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

production:
  # ...
  encoding: utf8mb4
  collation: utf8mb4_bin

import sys
sys.version

sc.version

$ dig -x ip-address

% echo "test message" | sendmail -v reciver@me.com

$ docker ps -a

$ docker build -t pyspark3:latest -f Dockerfile .

$ docker run -it -v $(pwd):/opt/doc/working_dir -p 8888:8888 --name work pyspark3

$ docker start -ai work

$ docker stop work

$ hdfs dfs -ls /

$ hdfs dfsadmin -report