Skip to content

Index#

  • 10 min read

Prepping up for and passing the AWS Certified Solution Architect - Associate

On May 11th I passed the AWS Certified Solution Architect Associate exam which was harder then I expected. In this memo I will outline how I prepared to this exam, what topics you better pay more attention to and some tips and hints I could give to anyone going for AWS CSA exam.

Disclaimer: I took the original AWS CSA exam, not the one that was launched in Feb 2018; this older version is only available to schedule till August 2018. After that date the newer version of this exam will be the only one available. Watch out, it has a new set of objectives.

  • 4 min read

Uploading multiple files to AWS S3 in parallel

Have you ever tried to upload thousands of small/medium files to the AWS S3? If you had, you might also noticed ridiculously slow upload speeds when the upload was triggered through the AWS Management Console. Recently I tried to upload 4k html files and was immediately discouraged by the progress reported by the AWS Console upload manager. It was something close to the 0.5% per 10s. Clearly, the choke point was the network (as usual, brothers!).

Comer here, Google, we need to find a better way to handle this kind of an upload.

  • 2 min read

How to add YAML highlight in Highlight.js?

Haters gonna hate YAML, thats for sure. I am on the other hand in love with YAML; when one have to manually write/append config files I find YAML easier than JSON (and you have comments too).

Ansible, various static-site-generators and quite a lot of opensource tools use YAML syntax for the configuration purposes.
But still, YAML syntax highlighting is not a part of the Common languages shipped with highlight.js compiled package.

  • 4 min read

SR OS Rootifier or how to flatten 7750 SR config

Back in the days when I mostly did routing stuff I spent the whole day configuring SROS devices via SSH. And once in a while I saw that SSH session or its server part (or even underlying connection) glitched, resulting in a corrupted lines feeded to the device.

What was also quite common is to make a mistake (i.e. syntax one) in a single line and watch like the rest of config got applied to the wrong context.

These sad facts pushed me to create a rootifier CLI script, that was converting tree-like SROS config into flattented (aka rooted) fashion.

rootifier

update 2023

The web service that was available publicly but has been now decommissioned due to the transition to MD-CLI.

  • 8 min read

Flask application in a production-ready container

Flask documentation is very clear on where is the place for its built-in WSGI application server:

Note

When running publicly rather than in development, you should not use the built-in development server (flask run). The development server is provided by Werkzeug for convenience, but is not designed to be particularly efficient, stable, or secure.

So how about I share with you a Dockerfile that will enable your Flask application to run properly and ready for production-like deployments? As a bonus, I will share my findings discovered along the way of building this container image.

nginx-uwsgi-flaks-alpine-docker

  • 2 min read

Waiting for SSH service to be ready with Paramiko

Today I faced a task which required first to establish an SSH tunnel in a background process and later use this tunnel for SSH connection. What seemed like a child's play first actually had some fun inside.

A problem were hidden right between the moment you spawned ssh process in the background and the next moment you tried to use this tunnel. In other words, it takes literally no time to spawn a process in the background, but without checking that tunnel is ready, you will quite likely receive an error, since your next instructions will be executed immediately after.

Consequently, I needed a way to ensure that the SSH service is ready before I try to consume it.

  • 2 min read

Changing Libvirt bridge attachment in a running domain aka on-the-fly

At work I always prefer KVM hosts for reasons such as flexible, free and GUI-less. Yet I never bothered to go deeper into the networking features of Libvirt, so I only connect VMs to the host networks via Linux Bridges or OvS. Far far away from fancy virtual libvirt networks.

Even with this simple networking approach I recently faced a tedious task of reconnecting VMs to different bridges on-the-fly.
My use case came from a need to connect a single traffic generator VM to the different access ports of virtual CPEs. Essentially this meant that I need to reconnect my traffic generator interfaces to different bridges back and forth:

Apparently there is no such virsh command that will allow you to change bridge attachments for networking devices, so a bit of bash-ing came just handy.

  • 1 min read

Installing xrdp 0.9.1 on Ubuntu 16.04 Xenial

xrdp is defacto the default RDP server for Linux systems sharing with VNC the remote access solution olympus. I personally found it more resource friendly and feature rich compared to VNC solutions I tried.

The only problem I found with xrdp is that current Ubuntu LTS release Xenial 16.04 has a way outdated 0.6.1-2 version of xrdp in the packages repo. This version has no shared clipboard support, which makes remote support/remote access a tedious task.

xrdp currently in its 0.9.3 version and it would be really nice to have a more recent package, rather than installing it from sources, like many solutions propose.

Well, no need to compile xrdp from sources (unless you want to), because you can leverage a ppa from hermlnx that has xrdp 0.9.1-7 already built for amd64 and i386 systems

# all you need is
sudo add-apt-repository ppa:hermlnx/xrdp
sudo apt-get update
sudo apt-get install xrdp

You can also try a deb package of xrdp 0.9.2 -- https://github.com/suminona/xrdp-ru-audio

  • 1 min read

How to install python3 in Amazon Linux AMI

While Amazon Linux AMI has yum as a package manager, it is not that all compatible with any RHEL or CentOS distributive. A lot of changes that AWS team brought into this image made it a separate distro, so no eyebrows should be given when battle-tested procedure to install python3 will fail on Amazon Linux. (Yeah, python3 does not come included yet in Amazon Linux)

Fortunately it is very easy to fetch (while not the latest release) python3:

# list available packages that have python3 in their name
yum list | grep python3

# install python3+pip, plus optionally packages to your taste
sudo yum install python35 python35-devel python35-pip python35-setuptools python35-virtualenv

# update pip3. optionally set a symbolic link to pip3
sudo pip-3.5 install --upgrade pip

And that is it!

  • 2 min read

Yang Explorer in a docker container based on Alpine

I wrote about the Yang Explorer in a docker quite some time ago, Yang Explorer was v0.6 at that time. Back then the motivation to create a docker image was pretty simple -- installation was a pain in v0.6, it is still a pain, but the official version bumped to 0.8(beta).

So I decided to re-build an image, now using Alpine Linux as a base image to reduce the size.