MacBook unplugged from external monitor thinks it's still the Secondary Desktop

Command + Brightness Up is the keyboard shortcut for Detect Displays

src: https://apple.stackexchange.com/a/58952

Faster Time Machine backups on macOS

This seems to speed up TimeMachine backups:

sudo sysctl debug.lowpri_throttle_enabled=0


To restore normal slow speed use:

sudo sysctl debug.lowpri_throttle_enabled=1

RVM and SSL certificates

When on Mac while 'bundle install' or 'bundle update' you get following error:

Could not verify the SSL certificate for https://rubygems.org/.

There is a chance you are experiencing a man-in-the-middle attack, but most

likely your system doesn't have the CA certificates needed for verification. For

information about OpenSSL certificates, see http://bit.ly/ruby-ssl. To connect

without using SSL, edit your Gemfile sources and change 'https' to 'http'.

then try to use this

sudo rvm osx-ssl-certs update all 

Mac OS X Sierra and self signed certificates

For some reason after upgrading to Sierra some of self signed certificates stopped being trusted.
Keychain Access was hanging and guru meditating while trying to delete/reinstall certificate.

this helps to reinstall self signed certificate:


0. find your certificate among installed

security find-certificate -a -Z|grep -e "SHA\|alis"

1. remove cert with

security delete-certificate -Z certSha

2. install cert via command line

sudo security add-trusted-cert -d -r trustAsRoot -p ssl myCoolSelfSigned.cer

3. in Keychain Access in system keychain open certificate and select "Always Trust"


as well this tool does magick

sudo certtool i myCert.crt

Ruby Prime numbers

Ruby is the only language that has all the prime numbers in a set.

Prime

The set of all prime numbers.

See Ruby Doc on Prime 

it's like "Chuck Norris Has Counted To Infinity. Twice" 

Just kidding - basically, the class provides Enumerable type API to prime number generator with limitation to methods 'each' and 'first', but I like the Ruby Doc description :-)