FranklinHarry

Vim cheat sheet

Starting Vim

vim [file1] [file2] ...

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FranklinHarry

# to generate your dhparam.pem file, run in the terminal
openssl dhparam -out /etc/nginx/ssl/dhparam.pem 2048

FranklinHarry

The default formula use by AWS RDS to calculate the max_connections parameter is: LEAST({DBInstanceClassMemory/9531392},5000)

But It's hard to find the exact value of DBInstanceClassMemory.

So, here are the values I got when I ran the SQL commmand: show max_connections; in some RDS instances:

Instance type	RAM (GB)	max_connections
db.t2.small	2	198
db.t2.medium	4	413

FranklinHarry

BIND for the SMALL LAN

How to configure BIND 9 to act as a caching nameserver or as the nameserver for a local domain.

Contents

• Why serve DNS locally?
• Building a caching nameserver

FranklinHarry

kubectl get services                # List all services 
kubectl get pods                    # List all pods
kubectl get nodes -w                # Watch nodes continuously
kubectl version                     # Get version information
kubectl cluster-info                # Get cluster information
kubectl config view                 # Get the configuration
kubectl describe node <node>        # Output information about a node
kubectl get pods                         # List the current pods
kubectl describe pod <name>              # Describe pod <name>
kubectl get rc                           # List the replication controllers

FranklinHarry

; Sample supervisor config file.

[unix_http_server]
file=/tmp/supervisor.sock   ; (the path to the socket file)
;chmod=0700                 ; sockef file mode (default 0700)
;chown=nobody:nogroup       ; socket file uid:gid owner
;username=user              ; (default is no username (open server))
;password=123               ; (default is no password (open server))

;[inet_http_server]         ; inet (TCP) server disabled by default

FranklinHarry

Requirements

• no upfront installation/agents on remote/slave machines - ssh should be enough
• application components should use third-party software, e.g. HDFS, Spark's cluster, deployed separately
• configuration templating
• environment requires/asserts, i.e. we need a JVM in a given version before doing deployment
• deployment process run from Jenkins

Solution

FranklinHarry

#!/bin/bash

target_branch="production"
working_tree="PATH_TO_DEPLOY"

while read oldrev newrev refname
do
    branch=$(git rev-parse --symbolic --abbrev-ref $refname)
    if [ -n "$branch" ] && [ "$target_branch" == "$branch" ]; then
    

FranklinHarry

#!/bin/sh

# Check to see if we are on master branch. Stop accidental commits
if [ $(git symbolic-ref HEAD 2>/dev/null) == "refs/heads/master" ]
then
  echo "Cannot commit to master branch"
  exit 1
fi
exit 0

FranklinHarry

#!/bin/bash

set -eux

create_commit() {
    git checkout "$1"
    echo "$2" > src.txt
    git commit -am "$2"
    git log --graph --pretty=format:'%s %C(yellow)%d%Creset'
    sleep 2  # make the commits distinctive in time