Speed test site

A quite nice speed test that I used to finetune my SQM-QOS. Its all HTML5 without the need for any flash plugins https://www.dslreports.com/speedtest 

Resurrecting a bricked router

A couple of days ago, I tried to install dd-wrt to a top link router I purchased. I have another router of the same model which works perfectly with dd-wrt so I was surprised when the new one was bricked by the installation.

Apart from throwing it away the only alternative would be to try using the router serial port and tftp to upload new firmware.

In order to do that we need to solder the serial pins on the router board, have a serial to ttl device that will allow us to open the serial port from a computer.

I did not have a usb-ttl device so I tried to use an arduino clone I had. All of these devices that have a USB port have an internal usb-ttl that we can highjack to open a serial port. After that all we need is a tftp server to serve the new image.

The commands can be found on the internet. I tried various images the only one that worked was open wrt which was installed without problem. Not the router is working perfectly.

Here are some similar instructions for a Xiaomi router, one of the most affordable systems out there that can be loaded with OpenWrt https://dzone.com/articles/hacking-into-xiaomi-mi-router-3g-and-openwrt-firmw

Opensource platform for building blockchain applicateins

I stumbled on this project https://www.multichain.com/
There are quite a few blog posts, in the website about the platform and some interesting presentations:

https://www.multichain.com/blog/2017/04/video-difference-blockchain-database/

Systemd not so known options

We use systemd all the time to restart services and query for their status, but it can do a lot more than just that.

It can be used to analyse the boot time of the system (systemd-analyze), to display realtime information of the processes in a top like manner (systemd-cgtop), display the status of the whole system in a tree like manner (sudo systemctl status) and many more.

Of course none of these is new, you can do this in a number of different ways, but it seems systemd is replicating a number of other tools.

Following a symbolic link in linux

Sometimes a link is pointing to a link, that is pointing to a link etc. It is a pain to resolve all the links and find which is the final file.
But there is a command that you can use to make things easier, and it is called readlink.

readink -f filename will traverse all the paths and print out the final filename

Moving a zfs pool from one disk to another

If we want to move a zfs pool with their full layout from one disk to another we can use the following approach

zfs snapshot -r pool_A@migrate
zfs send -R pool_A@migrate | zfs receive -F pool_B

zfs unmount oldpool/myfilesystem

And take a new snapshot.

zfs snapshot oldpool/myfilesystem@snapshot2

you can now do an incremental send of the difference between the two snapshots which should be very quick.

zfs send -i oldpool/myfilesystem@snapshot1 \
             oldpool/myfilesystem@snapshot2 | zfs receive newpool/myfilesystem

Converting markdown presentation to pdf

If we want to convert a presentation from markdown to pdf, while keeping the slide format we can use the following command:

pandoc -t beamer -s -o habitat-presentation.pdf habitat-presentation-pdf.md