sensei-wu

A step by step comparison of ENTRYPOINT and CMD commands of docker

Theory

Both ENTRYPOINT and CMD are commands which are used for customizing the startup behavior of a container.

Both commands can be used interchangeably to serve similar purposes, but nevertheless there are subtle differences between them.

ENTRYPOINT is the right way to specify a startup command for a container.

troyharvey

# Use envFrom to load Secrets and ConfigMaps into environment variables

apiVersion: apps/v1beta2
kind: Deployment
metadata:
  name: mans-not-hot
  labels:
    app: mans-not-hot
spec:
  replicas: 1

thesandlord

# Copyright 2017, Google, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
FROM node:6-onbuild
EXPOSE 3000
ENV LANGUAGE English
ENV API_KEY 123-456-789

makeittotop

Out of Memory (OOM) refers to a computing state where all available memory, including swap space, has been allocated.

Normally this will cause the system to panic and stop functioning as expected.
There is a switch that controls OOM behavior in /proc/sys/vm/panic_on_oom. 
When set to 1 the kernel will panic on OOM. 
A setting of 0 instructs the kernel to call a function named oom_killer on an OOM.
Usually, oom_killer can kill rogue processes and the system will survive. 
The easiest way to change this is to echo the new value to /proc/sys/vm/panic_on_oom.

# cat /proc/sys/vm/panic_on_oom 1

Kartones

PSQL

Magic words:

psql -U postgres

Some interesting flags (to see all, use -h or --help depending on your psql version):

• -E: will describe the underlaying queries of the \ commands (cool for learning!)
• -l: psql will list all databases and then exit (useful if the user you connect with doesn't has a default database, like at AWS RDS)