How to access remote servers

Exercise #0 Install tools

Below are instructions to set up SSH and SSHFS for connecting to and downloading files from remote servers.
I recommend setting it on a terminal, but GUI (Graphical User Interface) alternatives are also included.

0.1) SSH: Sending commands to a remote server (Secure SHell Protocol)

Install using Putty, a GUI (Graphical User Interface)

Windows https://www.ssh.com/academy/ssh/putty/windows
Linux https://www.ssh.com/academy/ssh/putty/linux
Mac https://www.ssh.com/academy/ssh/putty/mac

Install using Terminal

The ssh command is preinstalled on Linux and Mac

0.2) SSHFS: Accessing files on a remote server (Secure SHell FileSystem)

Install using an GUI (Graphical User Interface)

Mac and Linux

https://filezilla-project.org (download the client and not the server)
Windows

https://winscp.net/eng/docs/guide_install

Install using Terminal : Linux and Mac only

Linux (from terminal)
```
sudo apt-get install sshfs
```
Mac
- Download OSXFuse and SSHFS from https://osxfuse.github.io

Install both .dmg files (stable releases)

Panoply: Visualizing netcdf files

Download in https://www.giss.nasa.gov/tools/panoply/download/
You may need to update java https://www.java.com/de/download/manual.jsp
Alternative on linux: ncview
```
sudo apt-get install -y ncview
```

Panic button: Jupyterhub

If something fails, you can still use the online alternative at https://jupyterhub.dkrz.de/hub/home
- Levante+Preset -> Start
  - For SSH:
    - Other -> Terminal
  - To Download:
    - Sidebar -> Download (right click)

EXERCISE #1 SSH :First login on LEVANTE (~5min)

1.1) Login into LEVANTE (local)

What you need
- Your account number (“MyUser”)
- Your password (“MyPASSWORD”)
Log into levante using your user and password (platform dependent)
- In the terminal (Mac and Linux)
```
ssh MyUser@levante.dkrz.de # replace MyUser
```
- With putty:
  - follow instructions in https://www.ssh.com/academy/ssh/putty/windows

1.2) Now on LEVANTE (remote)

Write a note

echo "My First Note" > note.txt
cat note.txt

Copy a netcdf file to your home directory, and check

cp /work/bb1224/userspace/b380602/ECHAM.climatology.2003_2012.nc ~/
ls -la 

EXERCISE #2 SSHFS: First disk mount from LEVANTE (~5min)

2.1) On a new terminal (local)

In the terminal (Mac and Linux)

MyUser=MyUser #replace right side with your user
MyPass=MyPass #replace right side with your pass
mkdir LEVANTE
sshfs $MyUser@levante.dkrz.de: ./LEVANTE -ovolname=NAME -o password_stdin <<< "$MyPass"

Read note
```
cat LEVANTE/note.txt
```

Open netcdf file

open LEVANTE/ECHAM.climatology.2003_2012.nc

With FileZilla:
- Connect
  - File -> Site Manager -> New site
    - “General” Tab
      - Protocol: SFTP
      - Host: levante.dkrz.de
      - User: MyUser (replace)
      - Password: MyPass (replace)
    - “Connect” -> yes
- Read note
  - On Local site (left side of window):
    - Make and enter a directory (e.g, “LEVANTE”) where you will download remote files
  - On Remote site (right side of window):
    - Search “note.txt”
      - Double click -> Open from local site (left side of window)
      - or: Right click -> View/edit
- Open netcdf file
  - On Remote site (right side of window):
    - Search “ECHAM.climatology.2003_2012.nc”
      - Double click -> Open from local site (left side of window)
      - or: Right click -> View/edit

EXERCISE #3 Panoply: Plot a netcdf file (~5 to 30min)

3.1) Find tutorials in https://www.giss.nasa.gov/tools/panoply/help/ (First 3 videos, 3 min each)

If you completed excercise 2, then “ECHAM.climatology.2003_2012.nc” is already open with panoply
Plot “aclcov” variable (total cloud cover)
- Double click on variable
- make a Lat-Lon map
- make a zonal average plot
- make a latitude-time contour plot (Hovmöller diagram)

Plot wind “u10” and “v10” variables

combine variables in the same plot

plot a map with the difference u10 - v10 (“arrays”)
plot a map with the vector magnitude (“arrays”)

EXERCISE #4 VIM : Change a text file (~5 to 60 min)

Vim is a great tool because it allows you to directly modify files on remote servers.
Plus, you won’t need to use your mouse again.

Learn vim if you haven’t, for example:

My recommendation: vimtutor (~30 min practical tutorial)
- just type
```
vimtutor 
```
- in the terminal and press enter.
- Follow at least until Lesson 4.2
Alternative tutorials:

on LEVANTE

copy a template file to your current folder and open it

cp /work/bb1224/userspace/b380602/namelist.echam ./
vi namelist.echam

now on vim, use the search function and search for
```
nauto          = 2
```
and change it to
```
nauto          = 1
```
save and check

EXERCISE #5 BASH: Learn the basic commands

Similarly, BASH commands on the terminal allow you to do everything you would normally do in files with your mouse (copy, move, delete files, etc…) directly on a remote server.
The most used bash commands are : https://www.educative.io/blog/bash-shell-command-cheat-sheet
A general tutorial : https://linuxconfig.org/bash-scripting-tutorial-for-beginners