INT 21h

Hi, I am Vladimir Smagin, SysAdmin and

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Мой QR Code Generator

№ 12000 В разделе Programming от May 27th, 2023,
В подшивках: Go

Мой собственный генератор QR кодов, создавался для моих сайтов и сервисов. Отлично работает в облаках и прочих средах. Написан на Golang.

Репозиторий с кодом и полными инструкциями https://git.blindage.org/21h/qr-generator-service

Сервис умеет в ограничение списка доменов и принимает GET и POST запросы по урлу /qr:

$ curl -vs -X POST -d '{"URL":"http://blindage.org/"}' http://localhost:8080/qr -o qr.png
*   Trying 127.0.0.1:8080...
* Connected to localhost (127.0.0.1) port 8080 (#0)
> POST /qr HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.81.0
> Accept: */*
> Content-Length: 30
> Content-Type: application/x-www-form-urlencoded
> 
} [30 bytes data]
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Content-Type: image/png
< Date: Fri, 26 May 2023 21:25:17 GMT
< Content-Length: 430
< 
{ [430 bytes data]
* Connection #0 to host localhost left intact

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Golang: set variable during build

№ 11467 В разделе Programming от December 12th, 2021,
В подшивках: Go

Useful to set version or build number. Also you can use embed.

Code:

package main

import "fmt"

var MyVariable = "jopa"

func main() {
	fmt.Printf("%s\n", MyVariable)
}

Build script:

#!/usr/bin/bash

ENVVAR="jopa i piska"

LDFLAGS=(
  "-X 'main.MyVariable=${ENVVAR}'"
)

go build -o testvar -ldflags="${LDFLAGS[*]}" main.go
./testvar

rm -f ./testvar

Output:

$ ./build.sh 
jopa i piska

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Python скрипт для быстрого получения токена из Селектел

№ 11253 В разделах: Programming Sysadmin от March 21st, 2021,
В подшивках: Python, Security, Selectel

Получает токен по логину и паролю и отдает в виде строки без переносов. Крайне удобно использовать в bash скриптах. Пример использования в моем наборе скриптов для получения сертификатов LetsEncrypt для хранилища Селектел https://git.blindage.org/21h/certbot-for-selectel

import argparse
import requests

parser = argparse.ArgumentParser("get_selectel_token")
parser.add_argument("account", help="Your master account or subaccount, i.e. 83522 or 43544_somename", type=str)
parser.add_argument("password", help="Password for this account", type=str)
args = parser.parse_args()

headers = {'X-Auth-User': str(args.account), 'X-Auth-Key': str(args.password)}
response = requests.get("https://api.selcdn.ru/auth/v1.0", headers=headers)
if response.status_code == 204:
    print(response.headers['X-Auth-Token'], end="")
else:
    print("Error:", response.status_code)

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Smooth LED blink on Arduino, ESP8266, etc

№ 11244 В разделах: Electronics ESP8266 Programming от March 8th, 2021,
В подшивках: Arduino, ESP8266

Human eye can’t see led switching because its too fast, same effect used in old TV and displays with CRT, most of 7-segment indicators and other things. Change timings between on and off state to change brightness and effect duration.

int sv_max=20;
int sv_min=0;

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  int pause_on=sv_min;
  int pause_off=sv_max;
  // Smooth turn on
  while(pause_on < sv_max) {
    pause_on++;
    pause_off--;
    digitalWrite(LED_BUILTIN, HIGH);
    delay(pause_on);
    digitalWrite(LED_BUILTIN, LOW);
    delay(pause_off);
  }
  pause_on=sv_max;
  pause_off=sv_min;
  // Smooth turn off
  while(pause_on > sv_min) {
    pause_on--;
    pause_off++;
    digitalWrite(LED_BUILTIN, HIGH);
    delay(pause_on);
    digitalWrite(LED_BUILTIN, LOW);
    delay(pause_off);
  }
}

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Credentials and other secrets from Vault to your containers at startup

№ 11183 В разделах: Programming Sysadmin от January 2nd, 2021,
В подшивках: Docker, Go, Kubernetes, Security, Vault

What if you stored your database credentials in Vault and want to make ENV variables with them for your application at container startup? You can do it for Kubernetes deployments or plain Docker containers with my small program vault-envs.

Add to your Dockerfile additional steps:

install my vault-envs programs that “converts” secret to ENV variables
create\modify entrypoint script where or call vault-envs and other pre-startup actions

Add to your Dockerfile steps:

...
...
# add Ubuntu\Debian repo and install vault-envs with fresh certificates
RUN curl http://deb.blindage.org/gpg-key.asc | apt-key add - && \
    echo "deb http://deb.blindage.org bionic main" | tee /etc/apt/sources.list.d/21h.list && \
    apt update
RUN apt install -y ca-certificates vault-envs

# copy entrypoint script
COPY entrypoint.sh /entrypoint.sh
RUN chmod +x /entrypoint.sh

ENTRYPOINT ["/entrypoint.sh"]

Your entrypoint script will look like:

#!/bin/bash

...
...

export eval `vault-envs -token "$VAULT_TOKEN" \
        -vault-url https://vault.blindage.org \
        -vault-path /prod/crm/connection_postgres -envs-prefix "PG_"`

export eval `vault-envs -token "$VAULT_TOKEN" \
        -vault-url https://vault.blindage.org \
        -vault-path /prod/crm/connection_mysql -envs-prefix "MYSQL_"`

export eval `vault-envs -token "$VAULT_TOKEN" \
        -vault-url https://vault.blindage.org \
        -vault-path /prod/crm/connection_api`

...
...

exec "$@"

If some vars names is identical they will be overwritten at next vault-envs call, so I used prefix.

Now build image and run

docker run --rm -e VAULT_TOKEN=s.QQmLlqnHnRAEO9eUeoggeK1n crm printenv

and see results at container console:

...
VAULT_RETRIEVER=vault-envs
PG_DB_PASS=postgres
PG_DB_PORT=5432
PG_DB_USER=postgres
PG_DB_HOST=db-postgres
PG_DB_NAME=crm
MYSQL_DB_HOST=mysql.wordpress
MYSQL_DB_PASS=
MYSQL_DB_PORT=3306
MYSQL_DB_USER=root
MYSQL_DB_NAME=wordpress
API_HOST=http://crm/api
API_TOKEN=giWroufpepfexHyentOnWebBydHojGhokEpAnyibnipNirryesaccasayls4
...

Wooh! You did it.

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