SSH

ssh-config stuff and how to log into a server

by anna koitschev and linnea kempf

if you want to login via windows10, you should use ubuntu a subsystem for linux.
if you are a mac-user, you shuld install iterm2

a quick introduction to ssh

ssh stands for "secure shell"
ssh is a safe encrytion method to ensure protectionwhile accessing a computer over a network. basically, it creates a secure channel for clients and remote servers to communicate safely
when using ssh, there are two kinds of "keys" that come into play for user authentication:
the private key is kept as a secret on the local machine. It is your personal key to the server
the public key is copied to the ssh server during the authentication process and locks the server shut. the private key can basically open the public key.
you can find information on how to install your personal public-private-key pair here in the wiki.

the .ssh folder

while creating your ssh keys, there are different files being created inside a folder called .ssh. this folder contains important information about your ssh key. In this folder you will find your private and public key, which allow you to securely enter remote servers like this one, known_hosts, a file listing all hosts to which the user has connected and the config file which allows users to define specific ssh configurations for different hosts.

a quick introduction to the ssh config file

the ssh config file is located inside your *.ssh folder* under the user's home directory
the ssh config file, or configuration file, is a text file containing all specifications of your ssh connection. it can be opened in any text editor.
ssh config files help configure the default values for ssh connections

to use a config file

you need:

access to the terminal
nano (a texteditor)
a remote server

the default location of a user specific config file is in the .ssh directory:

~/.ssh config

the systemwide configuration file for all users is in:

~/etc/ssh/ssh_config

these file locations should not be changed!

how are ssh config files used?

if the ssh config file is in the right place, run the ssh command with the right settings to pick up what is in the config file and if an ssh config file contains an host section,you could see something like this:

host hfg-coding

    HostName hfg.lehrer.com
    User user vornamenachname
    IdentityFile ~/.ssh/id_name

the ssh command connects to the remote host:

ssh hfg-coding

the config file saves you from typing in connection details every time you want to connect to a host. you can set up default values for all servers or tweak settings for specific ones using a chain of host options and wildcards.

how to create a ssh config file

open your terminal and navigate to the .ssh directory:
```
cd ~/.ssh
```
note: if the directory does not exist, you can create it by using mkdir like this:
```
mkdir ~/.ssh
```
use a text editor to create and open the config file. in this case our text editor is nano:

nano config

the editor creates an open file for editing. you can now fill out the file with information, close and save the changes using these commands:

ctrl o
ctrl x

give reding and writing permission to the current user only!

chmod 600 ~/.ssh/config

host hostname1
    parameter argument
    parameter argument
host hostname2
    parameter argument

cd ~/.ssh

cat config

host hfg-design_coding
        hostname hfg.lehrer.com
        user vorname-nachname
        identityfile ~/.ssh/privatname

ssh "host"