If you work in software, You would've definitely connected to a remote machine running on the cloud like aws, gcp, azure, etc. or running locally on your own computer through virtualization technologies like qemu/kvm, hyperv,vmware, etc. with SSH. Typically, An SSH session flow looks like this: Connect -> Do Task -> Disconnect.

Do you know that SSH can do more than this? I'll cover a few problems I found myself in and how SSH saved my day.

copy something from remote machine to local machine.

I ran a diagnostic tool on my remote machine and it generated a bunch of log files in my home directory on the remote machine. These files were too many to analyze remotely so I wanted to copy them from the remote machine to my local computer. How do I do it? I had several options but all of them involved uploading the logs somwhere on the internet from my remote machine and then downloading the logs onto my local machine. What if my logs were sensitive and I don't want to expose them to the bad internet?

Enter SSH! I found out you can just do,

# command: structure of the command
scp <username>@<remote_ip>:<absolute_remote_file_path> <relative_or_absolute_local_file_path>
 
# example: this would copy the file from remote path /home/ayush/sysdump.tar.gz to your current local directory.
scp ayush@10.0.191.144:/home/ayush/sysdump.tar.gz ./sysdump.tar.gz

access a service running on remote machine without exposing it to the internet.

The same diagnostic tool I ran previously on the remote macine had a web dashboard feature. I ran the dashboard on the remote machine and it was listening on 0.0.0.0:80. The problem was that this remote machine was completely isolated from the public internet with the only exception that I was allowed to connect to it via SSH. Therefore I couldn't just port forward the port 80 on my remote machine and access the dashboard through the public internet. So, How do I access the dashboard without messing with any network settings?

Enter SSH! I found out you can just do,

# command: structure of the the command
ssh -N -L <local_port>:<remote_server_bind_address>:<remote_server_ip>
 
# example: here the dashboard was listening on 0.0.0.0 &
# port 80 on remote machine
ssh -N -L 80:0.0.0.0:80 ayush@10.0.191.144
 
# few more examples
# - what if you have more than one service on remote machine?
# ssh has you covered! you can expose as many services as you like.
ssh -N -L 80:0.0.0.0:80 -L 5432:0.0.0.0:5432 -L 21:0.0.0.0:21 ayush@10.0.191.144
 
# - this also works for remote kubernetes services, say your service
# is running on 69.96.0.32 and port 443. you could do,
ssh -N -L 443:69.96.0.32:443 ayush@10.0.191.144

I was then able to access the dashboard as if it was running on my local machine via localhost:80.

so...now what?

Well! That's it. I hope you learnt something new. SSH is nice and now you can use these commands if you ever run into these situations. Thank you for reading. <3