==============================
Passwordless SSH Configuration						[TOC]
==============================

You can use your own computer for all exercises. But in addition you will also
need an account on our Unix server theon:

- For submitting your solution for a quiz (i.e. programming assignment)
- To access some additional material, e.g. source files.
- So that we can provide you some reference installation of certain tools (in
  case you have problems with a local installation).

You can use __this web form__ to register for an account on theon. Once your
account is active also __register for this lecture in SLC__.

---- VIDEO ------------------------------
https://www.youtube.com/embed/rF187vJoSps
-----------------------------------------

__Slides__

scp (Secure copy)
=================

Once the SSH configuration is complete you also can use __scp (secure copy)__
to passwordless copy one or more files from `theon` to your own computer forth
and back. 

---- VIDEO ------------------------------
https://www.youtube.com/embed/uZb8SP67knc
-----------------------------------------

Usage
-----

The usage of `scp` has the form

---- CODE ------------------
scp [options] sources target
----------------------------

Hereby `sources` can specify a single file or a list of files. In particular
you can use a wildcard like `*`. For example, `h*.c` expands to a list with all
filenames that begin with an `h` and end on `.c`. The list of names in
`sources` can refer files on a server or to local files:

- If a name begins with "`theon:`", e.g. `theon:foo`, it refers to the file
  `foo` on `theon`. The path of the file is by default relative to your home
  directory. So `theon:hpc0/session01/foo` refers to the file `foo` in your
  subdirectory `hpc0/session01`. And `theon:hpc0/session01/foo*` to all files
  in this subdirectory that begin with `foo`.

  Of course, if you use an absoulte path like in `theon:/home/numerik/pub/foo`
  it refers to the file `/home/numerik/pub/foo` on theon.

The same syntax is used for `target` to specify a destination that can be local
or remote. If `target` is a directory then files will be copied into this
directory, otherwise `target` is used as filename for the copy.

Some examples
-------------

- Copy the local file `foo` from the current directory to your home directory
  on `theon`:

  ---- CODE ----------
  scp foo theon:foo
  --------------------

  or (because we don't want to change the filename) simply

  ---- CODE ----------
  scp foo theon:.
  --------------------

  or even simpler

  ---- CODE ----------
  scp foo theon:
  --------------------

- Copy the local file `foo` from the current directory to your home directory
  on `theon` and rename it to `bar`:

  ---- CODE ----------
  scp foo theon:bar
  --------------------

- Copy from your home directory on `theon` the file `foo` to the current
  directory on your local machine:

  ---- CODE -----
  scp theon:foo .
  ---------------

Copying directories: Option `-r`
--------------------------------
For copying directories and all its subdirectories use the option `-r` (for
recursive):

- From the current directory you can copy the directory `hpc0` and everything it
  contains to your home directory on `theon` with

  ---- CODE --------
  scp -r hpc0 theon:
  ------------------

- With

  ---- CODE ---------
  scp -r theon:hpc0 .
  -------------------

  you copy the directory `hpc0` from your home directory on `theon` to the
  current directory on your local computer

Exercise
========
Copy your directory `hpc0` from your local computer to `theon`. Then copy it
back.


:links: this web form -> https://anmelden.mathematik.uni-ulm.de/cgi-bin/slcreg
        scp \(secure copy\) -> https://en.wikipedia.org/wiki/Secure_copy_protocol
        register for this lecture in SLC -> https://slc.mathematik.uni-ulm.de/portal/catalog/details/term/SS2022/lecture/993
	Slides -> https://www.mathematik.uni-ulm.de/numerik/hpc/ss22/hpc0/slides/HPC0 Passwordless SSH.pdf