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Processing JSON using jq

jq is useful to slice, filter, map and transform structured json data.

Installing jq

On Mac OS

brew install jq

Change default DNS nameserver used by Kubernetes pods

This can be applied generically but usually applies to Linux nodes that have a local caching nameserver running, which means pointing to an IP in the loopback range (127.0.0.0/8). Ubuntu 18.04 Bionic Beaver does this by default.

Option 1: Change host configuration

sudo systemctl mask systemd-resolved
rm -f /etc/resolv.conf
sudo ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf

Common Options

-#, --progress-bar Make curl display a simple progress bar instead of the more informational standard meter.

-b, --cookie <name=data> Supply cookie with request. If no =, then specifies the cookie file to use (see -c).

-c, --cookie-jar <file name> File to save response cookies to.

Docker - How to cleanup (unused) resources

Once in a while, you may need to cleanup resources (containers, volumes, images, networks) ...

delete volumes

// see: https://github.com/chadoe/docker-cleanup-volumes

$ docker volume rm $(docker volume ls -qf dangling=true)

$ docker volume ls -qf dangling=true | xargs -r docker volume rm

	-- show running queries (pre 9.2)
	SELECT procpid, age(clock_timestamp(), query_start), usename, current_query
	FROM pg_stat_activity
	WHERE current_query != '<IDLE>' AND current_query NOT ILIKE '%pg_stat_activity%'
	ORDER BY query_start desc;

	-- show running queries (9.2)
	SELECT pid, age(clock_timestamp(), query_start), usename, query
	FROM pg_stat_activity
	WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%'

	import { join } from 'path'
	import { readdir, stat } from 'fs-promise'

	async function rreaddir (dir, allFiles = []) {
	const files = (await readdir(dir)).map(f => join(dir, f))
	allFiles.push(...files)
	await Promise.all(files.map(async f => (
	(await stat(f)).isDirectory() && rreaddir(f, allFiles)
	)))
	return allFiles

	AWSTemplateFormatVersion: 2010-09-09
	Parameters:
	RootDomainName:
	Type: String
	Mappings:
	RegionMap:
	us-east-1:
	S3HostedZoneID: Z3AQBSTGFYJSTF
	S3WebsiteEndpoint: s3-website-us-east-1.amazonaws.com
	us-west-1:

	AWSTemplateFormatVersion: 2010-09-09
	Parameters:
	RootDomainName:
	Type: String
	Mappings:
	RegionMap:
	us-east-1:
	S3HostedZoneID: Z3AQBSTGFYJSTF
	S3WebsiteEndpoint: s3-website-us-east-1.amazonaws.com
	us-west-1:

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