Ssh

Connect to remote host with ssh keys

On the client

Prepare folder (if needed)

$mkdir ~/.ssh
$chmod 700 ~/.ssh
$cd ~/.ssh

Create a ssh key (if you don't have one !)

$ssh-keygen -t rsa -C "id_rsa"

Copy your pub certificate to remote

$scp -p id_rsa.pub remoteuser@remotehost

On the remote (server/client)

Connect to your remote server/client

$ssh remoteuser@remotehost

Prepare folder

$mkdir ~/.ssh
$chmod 700 ~/.ssh

Copy the key into a authorized file

IMPORTANT : You need to edit the authorized_keys on the right user, if you need to allow multiple user, you need to edit all “.ssh\authorized_keys” under all users !!

$touch ~/.ssh/authorized_keys
$cat id_rsa.pub >> ~/.ssh/authorized_keys
$chmod 600 ~/.ssh/authorized_keys

Remove password authentication and allow ssh connect RSA

Here i use webmin

webmin_ssh_rights

Connect with public key

$chmod -R 600(or 700 ?) id_rsa.priv.txt
$ssh -i id_rsa.priv root@IP

Source : sourceforge

Date : 2018.06.15

Regenerate ssh key

Delete old keys

$/bin/rm -v /etc/ssh/ssh_host_*

Reconfigure openssh-server

$dpkg-reconfigure openssh-server

Restart the service

$systemctl restart ssh

Update your client with new key

$ssh-keygen -R IP_of_your_server

Change ssh banner

Change the prompt

$nano /etc/issue

Change banner when logon

$nano /etc/motd

Edit the "etc/issue"

How to

$nano etc/issue
escape sequences :
\b -- Baudrate of the current line.
\d -- Current date.
\s -- System name, the name of the operating system.
\l -- Name of the current tty line.
\m -- Architecture identifier of the machine, eg. i486
\n -- Nodename of the machine, also known as the hostname.
\o -- Domainname of the machine.
\r -- Release number of the OS, eg. 1.1.9.
\t -- Current time.
\u -- Number of current users logged in.
\U -- The string "1 user" or " users" where is the number of current users logged in.
\v -- Version of the OS, eg. the build-date etc.

For example :

If “/etc/issue” file contain “Debian GNU/Linux \d”

Output look like :

Debian GNU/Linux Web Feb 22 2017

Source : cyberciti

Date : 2020.10.13