ZilchBloke

One Line ssh-keygen (ed25519) and ssh-copy-id for powershell. (windows client to linux server)

ssh-keygen -o -a 100 -t ed25519 -f $env:USERPROFILE\.ssh\server_key -C "ServerUsername@ServerHostname" && cat $env:USERPROFILE\.ssh\server_key.pub | ssh linuxUser@linuxServer "mkdir ~/.ssh/ ; touch ~/.ssh/authorized_keys ; cat >> ~/.ssh/authorized_keys"

Fill the above command with relatable entry for you

Variables	Description
server_key.pub	Filename of your public key. Located in `$env:USERPROFILE\.ssh\` . It could be `id_ed25519.pub` or `id_rsa.pub` or whatever. In this case it is `server_key.pub`
`-C "ServerUsername@ServerHostname"	'-C' is comment option and comment are written between " ", to relate the key to the server.
linuxUser	User of the server(linux machine)[in this case, linuxServer],with which we are using ssh to connect to the server.

ssh-copy-id for powershell. (Windows Client to Linux Server)

execute the command as an Administrator.
cat $env:USERPROFILE\.ssh\KeyToServer.pub | ssh "mkdir ~/.ssh/ ; touch ~/.ssh/authorized_keys ; cat >> ~/.ssh/authorized_keys"

ssh-keygen with ed25519 encryption

Generate `ed25519` keys for `ssh` in `~/.ssh/` default-directory with identifying filename and comment.

ssh-keygen -o -a 100 -t ed25519 -f ~/.ssh/server_key -C "ServerUsername@ServerHostname"

For windows :

ssh-keygen -o -a 100 -t ed25519 -f $env:USERPROFILE\.ssh\server_key -C "ServerUsername@ServerHostname"

ssh-keygen will create 2 keys file. Public Keys(with .pub) and Private Keys. |Options|Meaning|

Changing root password from GRUB (without using existing password)

For RHEL9

Steps

When the machine starts, after bios loads up, Grub menu appears (with 2 options for boot kernel)
Use the arrow key to highlight the rescue kernel (Out of 2 options one will specify to be ..rescue.. kernel) and press e
Use the arrow key to mve the crusor to the end of the line starting with linux..
At the end of the line, append rd.break and press Ctrl+x
mount -o remount,rw /sysroot/ to allow read and write permission to /sysroot/
chroot /sysroot/
passwd to change the password. Shell will prompt to type the new password and retype it to avoid typo.

SSH : Secure Shell is a cryptographic network protocol.
SSH protocol Architecture:
Two computers in secure shell communicate where one of them is client and the other is server.
And SSH provides cryptographic sheild to this communication.
client presents query
server responds to query

SSH in Windows - FULL [NO BS!]

Use Powershell 7.3 or up. as an Administrator.

To check the state of ssh package:

Get-WindowsCapability -Online -Name OpenSSH*

`ssh-agent`

For Windows:
Use Powershell (7.3 and above as an admin).
By default the ssh-agent service is disabled.
Configure it to start automatically.
Get-Service ssh-agent | Set-Service -StartupType Automatic
Start the service
Start-Service ssh-agent

>For Linux:

	pushd "%~dp0"
	dir /b %SystemRoot%\servicing\Packages\Hyper-V.mum >hyper-v.txt
	for /f %%i in ('findstr /i . hyper-v.txt 2^>nul') do dism /online /norestart /add-package:"%SystemRoot%\servicing\Packages\%%i"
	del hyper-v.txt
	Dism /online /enable-feature /featurename:Microsoft-Hyper-V -All /LimitAccess /ALL
	pause