ZubairLK

balenaOS Masterclass

Prerequisite Classes

This is the first balenaOS masterclass.

There are no prerequisites apart from basic linux knowledge and terminal access to a device running balenaOS.

Masterclass Type: Core Maximum Expected Time To Complete: 60 minutes

ZubairLK

root@5689936:~# chronyc sources -v
210 Number of sources = 4

  .-- Source mode  '^' = server, '=' = peer, '#' = local clock.
 / .- Source state '*' = current synced, '+' = combined , '-' = not combined,
| /   '?' = unreachable, 'x' = time may be in error, '~' = time too variable.
||                                                 .- xxxx [ yyyy ] +/- zzzz
||      Reachability register (octal) -.           |  xxxx = adjusted offset,
||      Log2(Polling interval) --.      |          |  yyyy = measured offset,
||                                \     |          |  zzzz = estimated error.

ZubairLK

Notes on making rachel pi work with a read-only filesystem.

A good reference this is based on. https://hallard.me/raspberry-pi-read-only/

List of actions:

1. Remove logging

ZubairLK

Ideally, go through https://docs.docker.com/engine/userguide/intro/
Its pretty good and steps through many various features.

Ubuntu repositories usually have an old version.
Install latest from https://docs.docker.com/engine/installation/linux/ubuntulinux/

To make it easy to run docker without sudo. Add current user to sudo.
https://docs.docker.com/engine/installation/linux/ubuntulinux/#create-a-docker-group

Run hello-world container.

ZubairLK

# sabaq.pk has a site-map page which has links to all videos.
# Extracting titles of all videos using the following bash for example punjab biology 9th class

# need a few variables
subject=punjab-biology-9th
board="punjab board"

# grep subject, then video. then replace bad characters in the line with nothing using sed to generate right urls of each video
cat sabaq.xml | grep $subject | grep video | sed s/vsg/sid/ | sed 's/amp;//' | sed 's/<loc>//' | sed 's/<\/loc>//' > $subject.txt

ZubairLK

sabaq.pk has lectures in urdu for high school.

They are hosted on daily motion.

The easiest way would be to download them all using youtube-dl and the sabaq user.

However they are not sorted as playlists, and the video titles are not numbered.
And daily motion has an issue. It only shows 1800 videos on a 100 user pages.

Any more video pages get redirected to the 100th page.

ZubairLK

youtube-dl is a nifty utility that can parse and download all user videos. Recently added a feature on downloading all playlists.

Here is a command that downloads all playlists of user KhanAcademyUrdu and puts all videos of each playlist in separate folders.

youtube-dl -ciw -f '(webm)[height<480]' -o '/media/zubairlk/part1/khanurdu/%(playlist)s/%(playlist_index)s_%(title)s_%(id)s.%(ext)s' --yes-playlist  -R 10000 https://www.youtube.com/user/KhanAcademyUrdu/playlists

some explanation for later. see https://github.com/rg3/youtube-dl for full details.

-i is to ignore interrupts. timeouts/private videos etc block otherwise.

ZubairLK

this is me typing in the main window