# granular-exp SETUP

###### tags: `experimental setup` `SoftQC` `self-assembly`

---

This is the documentation page for the computer monitoring the granular experiment.
It was mostly scrapped from the lab's bin. It should be enough to handle the small needs of our experiment for the moment.

# Computer

## To do

* Fix Wake on LAN

## Hardware

* 1 Intel Core 2 Duo E8400, 2 cores 3.0 GHz 6MB of cache
* 4 1GiB DDR2
* 1 80GB Samsung HDD on which the OS is installed
* 1 4TB Seagate HDD for data storage

## Network

* IPv4: 129.175.83.43
* IPv6: fe80::222:19ff:fe29:9f70
* DNS name: ?
* MAC: 00:22:19:29:9f:70

## OS

Lubuntu 20.04.2 LTS (Focal Fossa)

## Storage

The small disk of 80GB is used to host the OS and local files.
The large disk of 4TB is used for data storage. The idea is to not put files needed for daily operation here, to be able to take the disk out if we ever want a fast transfer of large amounts of data.

### Partitionning

Partitions on the system disk:
* 1.9GB ext4 partition for `/boot`
* 67.1GB xfs partition for `/`
* 5.6GB of swap

The storage disk contains a single 4TB xfs partition.

## Users

There are two users on the machine: "admin" and "user".
"user" password is "granular"

## Access
### SSH

The computer can be reached over ssh from the lab's network using

ssh user@129.175.83.43

This will prompt for the password, which is "granular".
To avoid having to type the address every time, a section can be added on the client machine in `~/.ssh/config`:

Host <name of you choice. eg: "granular_exp">
Hostname 129.175.83.43
User user

Now you only need to type `ssh granular_exp` to connect to the machine. The password will still be required though.
To avoid typing the password, you can use public key authentication. **The machine only accepts `ed25519` and `rsa` type public keys.** If you don't have a key pair already, you can generate one with:

ssh-keygen -t ed25519

or (if you use an old ssh client that does not support ed25519 keys)

ssh-keygen -t rsa -b 4096

Then, send your public key to the machine using

ssh-copy-id granular_exp

You can now connect to the computer by typing `ssh granular_exp` without being prompted for your password. Note that the generated private keys (`id_rsa` or `id_ed25519`) grant access to your account on every machine that knows about them, so they should be **kept secret**.

### Fail2ban

Fail2ban is running on the machine to prevent brute force attacks on ssh passwords.
If one enters a bad password more than 5 times in a 10 minutes window, its IP address is banned for the next 10 minutes.

The status of the jail can be checked by privileged users using

fail2ban-client status sshd

Fail2ban logs can be found in `/var/log/fail2ban.log`.

To unban an IP before the end of the sentence, run

fail2ban-client set sshd unbanip IP_ADDRESS_TO_UNBAN

# Experimental setup

The shaker and its friends have arrived !


On the left, is the amplifier with the function generator on top. On the right is the mighty shaker and in the middle sits the oversized air cooling fan.

We tested the setup with Frederic and François. It seems to work fine.
In the next days, François will order optical tracks to build a stand for the camera, and some anti-vibration plate to put the shaker on. He will also build a dirty test plate to start playing with the setup and identify possible problems. Then, we will ask engineers in the lab workshop for a more professionnal solution. On our side, we take care of the experiment computer.

The beads are on their way to the lab. Fred ordered 1.19mm, 2.381mm and 2.5mm in diameter, 10k of each.
We thought that one problem will be sorting beads of different type. For that, a sieve with hole slightly smaller than the big beads could be very handy.

# Samples