= SSH KEY GEN =


1. Create ssh key at localhost [[br]]

{{{
ssh-keygen -t rsa -b 4096 -C user@remotehost.com
}}}

 Then they will ask to enter default .ssh path
{{{
Enter file in which to save the key (/home/yourusername/.ssh/id_rsa):
}}}

 We can key in any passphrase to make extra security but just press enter with empty key it will automate gen-key for you
{{{
Enter passphrase (empty for no passphrase):
}}}

 Now the public and private key will be kept in
{{{
ls -al
/home/yourusername/.ssh/id_rsa /home/yourusername/.ssh/id_rsa.pub
}}}

2. In your local host copy public key (id_rsa.pub) to remote host

{{{
ssh-copy-id remote_username@server_ip_address
}}} 
 or with manual ssh with 
 {{{
 cat ~/.ssh/id_rsa.pub | ssh remote_username@server_ip_address "mkdir -p ~/.ssh && chmod 700 ~/.ssh && cat >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"
 }}}

3. Now you can ssh with out prompt for password

== Tunnel ssh ==

Ref [https://linuxize.com/post/how-to-setup-passwordless-ssh-login ref] [[br]]

Remote to local [[br]]
 At localhost user create tunnel to remote host with following
{{{
ssh -R 8022:localhost:22 remoteUser@remotehost.com
}}}
 Then, at remote host, user can '''ssh -p 8022 localUser@127.0.0.1''' to localhost

 If we want to bind to specific interface (NICs), we use
{{{
ssh -R 128.199.96.250:8022:localhost:22 krit@128.199.96.250
}}} 
 and at 128.199.96.250 server on /etc/ssh/sshd_config file add this line
{{{
GatewayPorts clientspecified
}}}
 Then user can access ssh -p 8022 128.199.96.250 will forward to client on this tunnel


Local to Remote
 At localhost user create tunnel to remote host with following
{{{
[krit@mini ~]$ ssh -L 2000:localhost:22 remoteUser@remotehost.com
}}}
 Then, at localhost, user can ''' ssh -p 2000 krit@127.0.0.1''' at localhost it will tunnel to remote host [[br]]

== ssh rsync ==

rsync from local to remote server via ssh we need to install '''apt install sshpass'''
{{{ 
#!sh
[omd@local Test]$ sshpass -p "password" /usr/bin/rsync -a ~/var/log/Rsync/out.txt krit@172.17.0.1:Tmp/Test
}}}

== ssh tunnel ==

At remote server that we would like to ssh in used following config with ssh_public key place at local server.

{{{
root@dwdm:/etc/systemd/system# more sshtunnel.service 
[Unit]
Description=SSH Tunnel
After=network.target

[Service]
Restart=always
RestartSec=20
User=root
ExecStart=/usr/bin/ssh -NT -o ServerAliveInterval=60 -o ExitOnForwardFailure=yes -R 32022:l
ocalhost:22 vodka@18x.1xx.217.xx


[Install]
WantedBy=multi-user.target
}}}