Mastering #Ansible Video #Course

#ansible part1 - Course Overview

#ansible part2 - Ansible requirements

In Django unittests you can use fixtures in order to create dummy data. To create fixtures you can use django dumpdata command to dump a specific data:

python3 manage.py dumpdata --indent 4 YOUR_APP.YOUR_TABLE > output_data.json

This is how you can dump data and use it as your data backend for unittests.

#django #python3 #dumpdata #unittest

Read more here:

https://coderwall.com/p/mvsoyg/django-dumpdata-and-loaddata

Working effectively with legacy code
#ebook #pdf #epub

How to delete a git branch?

https://makandracards.com/makandra/621-git-delete-a-branch-local-or-remote

#git #branch #delete

Is there a way to create ObjectID from an INT in MongoDB?

import bson

def object_id_from_int(n):
    s = str(n)
    s = '0' * (24 - len(s)) + s
    return bson.ObjectId(s)

def int_from_object_id(obj):
    return int(str(obj))

n = 12345
obj = object_id_from_int(n)
n = int_from_object_id(obj)
print(repr(obj))  # ObjectId('000000000000000000012345')
print(n)  # 12345

#mongodb #objectid #pymongo #python #bson #int

https://code-maven.com/serialize-datetime-object-as-json-in-python

#python #json #dump #datetime

https://tableplus.io/blog/2018/08/postgresql-how-to-find-and-kill-hanging-query.html

#postgres #kill #slow_query #postgreSQL

https://medium.com/@nielssj/docker-volumes-and-file-system-permissions-772c1aee23ca

#medium #docker #volumes #file_system

https://github.com/ab77/netflix-proxy

#proxy_server #proxy #netflix

To get an expiration time of a redis key you can use TTL like below:

TTL "YOUR_KEY_NAME"

To read more about setting expiration time and or other options:
- https://redis.io/commands/expire

#redis #expiration_time #expire #ttl

What does select_related do in Django?

select_related does a join in case needed on the DB side and reduce query counts. Let's look at an example:

# Hits the database.
e = Entry.objects.get(id=5)

# Hits the database again to get the related Blog object.
b = e.blog

In the above code 2 queries are issued in DB side. First it gets Entry record and then blog is fetched from DB when e.blog is called. And here’s select_related lookup:

# Hits the database.
e = Entry.objects.select_related('blog').get(id=5)

# Doesn't hit the database, because e.blog has been prepopulated
# in the previous query.
b = e.blog

You can follow foreign keys in a similar way to querying them. If you have the following models:

from django.db import models

class City(models.Model):
    # ...
    pass

class Person(models.Model):
    # ...
    hometown = models.ForeignKey(
        City,
        on_delete=models.SET_NULL,
        blank=True,
        null=True,
    )

class Book(models.Model):
    # ...
    author = models.ForeignKey(Person, on_delete=models.CASCADE)

Then a call to Book.objects.select_related('author__hometown').get(id=4) will cache the related Person and the related City:

# Hits the database with joins to the author and hometown tables.
b = Book.objects.select_related('author__hometown').get(id=4)
p = b.author         # Doesn't hit the database.
c = p.hometown       # Doesn't hit the database.

# Without select_related()...
b = Book.objects.get(id=4)  # Hits the database.
p = b.author         # Hits the database.
c = p.hometown       # Hits the database.

#python #django #select_related #join #database #models

https://xiaoxiaoke.wordpress.com/2015/10/06/changing-java-security-restriction-for-network-connect-error-issue-in-kvm/

#linux #devops #sysadmin #kvm #hp

https://www.toptal.com/python/introduction-python-microservices-nameko

#nameko #microservice #rabbitmq #python #docker #greenlet

How to SSH login without password?

You want to use Linux and OpenSSH to automate your tasks. Therefore you need an automatic login from host A / user a to Host B / user b. You don't want to enter any passwords, because you want to call ssh from a within a shell script.

How to do it?
First log in on A as user a and generate a pair of authentication keys. Do not enter a passphrase:

a@A:~> ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/a/.ssh/id_rsa):
Created directory '/home/a/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again: 
Your identification has been saved in /home/a/.ssh/id_rsa.
Your public key has been saved in /home/a/.ssh/id_rsa.pub.
The key fingerprint is:
3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A

Now use ssh to create a directory ~/.ssh as user b on B. (The directory may already exist, which is fine):

a@A:~> ssh b@B mkdir -p .ssh
b@B's password:

Finally append a's new public key to b@B:.ssh/authorized_keys and enter b's password one last time:

a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys'
b@B's password:

From now on you can log into B as b from A as a without password:

a@A:~> ssh b@B

#linux #sysadmin #ssh #password_less #ssh_login

How to get default gateway IP address?

ip route | grep default

The output would be something like below:

default via 192.168.1.1 dev eth0 onlink

NOTE: it can be different on your system

#linux #sysadmin #ip #route #default_gateway