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ssh

SSH Server​

  • OpenSSH

SSH Clients​

ssh config (client side)​

WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!​

ssh-keygen -R 192.168.3.10

SSH Port forwarding​

ssh -N -L <local-port>:<remote-host>:<remote-port> <user>@<remote-host>
  • -N restrics establishing a login shell to remote
  • -f shell runs in the background.
  • -T (Disable pseudo-terminal allocation) options so that I don’t get a tty connection on the (bastion/jump server)

Ref: https://builtin.com/software-engineering-perspectives/ssh-port-forwarding

ssh agent forwarding configuration in config file​

ForwardAgent

Ref: https://www.ssh.com/academy/ssh/config

Config file Reference​

ssh Man​

ssh proxy and jump host​

ssh config​

How do I disable remote SSH login as root from a server?​

/etc/ssh/sshd_config => PermitRootLogin no

Ref: https://askubuntu.com/questions/27559/how-do-i-disable-remote-ssh-login-as-root-from-a-server

Run ssh on specific port​

ubuntu@ip-172-31-13-46:~$ cat /etc/ssh/sshd_config

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options override the
# default value.

Include /etc/ssh/sshd_config.d/*.conf

Port 443
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

Auto SSH​

How Can I Set Up Reverse SSH Tunneling?​

Setting up this in real life is fairly straightforward if you work with open ports. Here’s a basic example:

  1. On LocalMachine:
ssh -R <Remote-Host-Port>:localhost:<Local-Host-Port> user@RemoteServer
ssh -R 9000:localhost:22 user@RemoteServer

Here, 9000 is the port on RemoteServer that will be used for the tunnel, and 22 is the SSH port of LocalMachine.

  1. On RemoteServer:
ssh -p 9000 user@localhost

How to check if ssh is running​

sudo systemctl status ssh

How to disable root remote login via ssh​

put the following line to /etc/ssh/sshd_config:

PermitRootLogin no

ssh config​

Host dev-vm
  HostName 192.168.0.5
  User ubuntu
  Port 22
  IdentityFile ~/.ssh/id_rsa
  # This forces ssh to use only the specified IdentityFile for authentication
  IdentitiesOnly yes

SSH is taking too long to login​

Edit your /etc/ssh/sshd_config to set GSSAPIAuthentication no