mowings

You'd like a docker container that runs cron jobs, with the output of those cron jobs going to stdout so they are accessible as docker logs. How do you do that?

Install cron, and set it up to run in the foreground

In your Dockerfile, apt-get -y install cron Use apk or whatever if you are running on alpine or another distribution Set the command or entrypoint in your Dockerfile to run cron 9n the foreground

ENTRYPOINT ["/usr/sbin/cron", "-f"]

mowings

Install pandoc, basic-tex and mermaid-filter

# brew install pandoc
# brew install --cask basictex
# npm i -g mermaid-filter

# Be sure to run the path_helper in an existing shell. Otherwise pdf-latex won't be found
# eval "$(/usr/libexec/path_helper)"

Convert an markdown to pdf

mowings

Use ffmpeg to stream video from a dahua 4300s to a file or files

You can use ffmpeg to directly pull frames off of a dahua 4300s at full resolution. May be a good alternative to pricey dvrs which likely cannot record at full resolution, may not work with the camera, or are prohibitevly expensive

Simple Stream to file

Simple stream to file. Full resolution

ffmpeg -loglevel debug -rtsp_transport tcp -i "rtsp://admin:admin@198.175.207.61:554/live" \

-c copy -map 0 foo.mp4

mowings

package main

import (
	"golang.org/x/net/websocket"
	"log"
	"net/rpc/jsonrpc"
)

// In a real project, these would be defined in a common file
type Args struct {

mowings

https://dev.to/aws-builders/how-to-run-a-shell-on-ecs-fargate-containers-eo1

Install session manager plugin locally

NOTE: It looks like the task default policy ALSO needs the ssm permissions as well. This CDK construct appears to copy those in; pulumi or other providers may not do the same.

Be sure that exec-command is set in the service definition. Via CDK:

mowings

#!/bin/bash

# Sometimes you want to sleep until a specific time in a bash script. This is useful, for instance
# in a docker container that does a single thing at a specific time on a regular interval, but does not want to be bothered
# with cron or at. The -d option to date is VERY flexible for relative times.
# See 
# https://www.gnu.org/software/coreutils/manual/html_node/Relative-items-in-date-strings.html#Relative-items-in-date-strings
# For details
# ALPINE USERS: You will need to install coreutils, as the built-in busybox date does not handle -d correctly.

mowings

Running multiple postgresql versions on the same Ubuntu 16 host

We start with postgres 9.3 installed from a self-build deb. We'd like to upgrqde to 9.6, but that requires both versions to be installed on the server. The idea is to add the new version directly from the repository, and adjust the data and log directories so both can run at the same time. We can then run pg_upgrade or a dump/restore to upgrade to a new cluster.

Steps:

# Create new data and log directories
mkdir /postgres/pg_data.new && chown postgres:postgres /postgres/pg_data.new
mkdir /mnt/pg_log.new && chown postgres:postgres /mnt/pg_log.new

mowings

There is a kernel option to do this, if it cauxes boot issues, but otherwise in /etc/rc.local you can just add

echo 1 > /sys/block/sdb/device/queue_depth

Normally the kernel disables it after too many errors automatically, but it can cause disk timeouts until that happens. Does not have much of a performance impact on ssds.

mowings

#!/bin/bash
interfaces=( $(netstat -in | egrep 'utun\d .*\d+\.\d+\.\d+\.\d+' | cut -d ' ' -f 1) )
rulefile="rules.tmp"
echo "" > $rulefile
sudo pfctl -a com.apple/tun -F nat
for i in "${interfaces[@]}"
do
  RULE="nat on ${i} proto {tcp, udp, icmp} from 192.168.64.0/24 to any -> ${i}"
  echo $RULE >> $rulefile
done

mowings

Diagrams as python code. Supports cloud infra as well as c4

https://diagrams.mingrammer.com/

Structerizr -- best for C4, UML. More for software arch.

https://github.com/structurizr/dsl/blob/master/docs/language-reference.md

C4 Home

https://c4model.com/