ssh – Pupli

Start Windows SSH Agent

May 13, 2025

Open PowerShell as Administrator.

Get-Service -Name ssh-agent | Set-Service -StartupType Automatic
Start-Service ssh-agent

Automatically Add SSH keys to the SSH agent upon Login

September 10, 2024September 10, 2024

You can configure your SSH client to automatically add your key when making an SSH connection.

Edit or create the SSH configuration file:
```
nano ~/.ssh/config
```
Add the following configuration:
```
Host *
    AddKeysToAgent yes
    IdentityFile ~/.ssh/id_rsa
```
Again, replace ~/.ssh/id_rsa with the path to your SSH key if necessary.
Save and close the file.

This will automatically add your SSH key to the agent whenever you initiate an SSH connection.

Restrict SSH login to only the public key method in Ubuntu

December 27, 2023

nano /etc/ssh/sshd_config

PermitRootLogin prohibit-password
PasswordAuthentication no
PubkeyAuthentication yes

systemctl restart sshd

Add SSH keys to an Ubuntu Server

December 27, 2023

Add your public key to the authorized keys file on remote server. To add you keys to the file, you can use the following command:

cat ~/id_rsa.pub >> ~/.ssh/authorized_keys

If you do not have the folder ~/.ssh/authorized_keys , you can create this with the following commands:

mkdir -p ~/.ssh
touch ~/.ssh/authorized_keys

References
https://medium.com/@williamkwao/how-to-add-ssh-keys-to-an-ubuntu-server-6a3a5b1bee26

Install Fail2ban on Ubuntu 22.04

May 10, 2023

sudo apt install fail2ban -y

sudo systemctl enable fail2ban
sudo systemctl start fail2ban

sudo systemctl status fail2ban

Configuring Fail2ban

sudo cp /etc/fail2ban/jail.conf /etc/fail2ban/jail. Local

sudo nano /etc/fail2ban/jail. Local

References
https://www.howtoforge.com/how-to-install-fail2ban-on-ubuntu-22-04/

Force SSH Client to Use IPv4 Only

April 25, 2022

Error while using port forwarding on SSH : Cannot assign requested address

You can force the use of IPv4 on the commandline with the -4 switch:

ssh -4 -L 8080:127.0.0.1:80 dev.local

References
https://www.electricmonk.nl/log/2014/09/24/ssh-port-forwarding-bind-cannot-assign-requested-address/
https://www.putorius.net/force-ssh-client-to-use-ipv4-or-ipv6.html

“Permissions 0777 for ‘id_rsa’ are too open” Error for SSH private Key

April 25, 2022

# Keys need to be only readable
chmod 400 ~/.ssh/id_rsa

Keys need to be read-writable
chmod 600 ~/.ssh/id_rsa

References
https://stackoverflow.com/questions/9270734/ssh-permissions-are-too-open-error

tunnel via multiple hops in SSH

April 11, 2021

I am working locally on localhost
host1 is accessible to localhost
host2 only accepts connections from host1
I need to create a tunnel from localhost to host2

You basically have three possibilities:

Tunnel from localhost to host1:
```
ssh -L 9999:host2:1234 -N host1
```
As noted above, the connection from host1 to host2 will not be secured.
Tunnel from localhost to host1 and from host1 to host2:
```
ssh -L 9999:localhost:9999 host1 ssh -L 9999:localhost:1234 -N host2
```
This will open a tunnel from localhost to host1 and another tunnel from host1 to host2. However the port 9999 to host2:1234 can be used by anyone on host1. This may or may not be a problem.
Tunnel from localhost to host1 and from localhost to host2:
```
ssh -L 9998:host2:22 -N host1
ssh -L 9999:localhost:1234 -N -p 9998 localhost
```
This will open a tunnel from localhost to host1 through which the SSH service on host2 can be used. Then a second tunnel is opened from localhost to host2 through the first tunnel.

Normally, I’d go with option 1. If the connection from host1 to host2 needs to be secured, go with option 2. Option 3 is mainly useful to access a service on host2 that is only reachable from host2 itself.

References
https://superuser.com/questions/96489/an-ssh-tunnel-via-multiple-hops

Debug Remotely on Android using adb via SSH Tunnel

August 23, 2020

Start adb daemon on remote device

adb devices

$ adb devices
* daemon not running. starting it now on port 5037 *
* daemon started successfully *
List of devices attached 
5200fe4259bcc000	device

do client to server port forwarding using ssh on port 5037

References
https://dontbelievethebyte.github.io/articles/2015/01/15/debug-remotely-on-android-via-ssh-tunnel/
https://developer.android.com/studio/command-line/adb
https://stackoverflow.com/questions/2604727/how-can-i-connect-to-android-with-adb-over-tcp

Copy files from one machine to another using ssh

March 9, 2020

scp <source> <destination>

To copy a file from B to A while logged into B:

scp /path/to/file username@a:/path/to/destination

To copy a file from B to A while logged into A:

scp username@b:/path/to/file /path/to/destination

References
https://unix.stackexchange.com/questions/106480/how-to-copy-files-from-one-machine-to-another-using-ssh