Mastering SSH and File Transfers to Remote servers: A Beginner's Handbook

Introduction¶

Do you find yourself baffled by the intricacies of SSH connections and file transfers to remote servers ?

Navigating the landscape of SSH connections, troubleshooting connection issues, and securely transferring files across servers can be a daunting task, especially for newcomers.

This guide is your compass in the world of SSH, unraveling the complexities and providing step-by-step instructions for establishing secure connections and transferring files seamlessly using Git Bash or WSL2 for Windows users and straightforward methods for Linux enthusiasts.

Whether you're a developer, sysadmin, or tech enthusiast stepping into the realm of remote server access or seeking efficient file transfer solutions, this guide is tailored to demystify SSH, troubleshoot common pitfalls, and equip you with the skills to maneuver through file transfers effortlessly.

This document break down the process of connecting via SSH and file transfer and should help someone new to SSH understand the process, troubleshoot common issues, and handle file transfers easily

Requirements¶

For windows users, use Git Bash installed on your computer or use wsl2 (for windows >=10)
For linux users, this should be straighforward

Connecting via SSH from cli¶

Steps to Connect¶

Open Terminal: Or search for Git Bash in your applications and open it.
Accessing the Server:
- Use the command
```
ssh {username}@{domain}
```
  or
```
ssh {username}@{server_ip}
```
- Replace {username} with your remote server username.
- Replace {domain} with the domain name or {server_ip} with the server's IP address.
Adding a Specific Port:
- If the server uses a different port (usually 22), use ssh {username}@{domain} -p {port}. Replace {port} with the correct port number.
Entering Credentials:
- After executing the command, you'll be prompted to enter your remote server account password. Type it in and press Enter.

Troubleshooting SSH Connection Issues¶

Error: "Unable to negotiate with... port..."¶

If you encounter the error Unable to negotiate with <IP> port <Port>: no matching host key type found. Their offer: ssh-rsa,ssh-dss

The Solution

Configure the client to accept the host key sent by the server.
Edit the ~/.ssh/config file:

Host {domain}
    HostKeyAlgorithms +ssh-rsa,ssh-dss

Use a text editor like Nano, Vim, or Notepad to modify the file.

Other Common SSH errors:

Permissions: Ensure correct file permissions for ~/.ssh and authorized_keys.
Network problems: Check firewall settings and network connectivity.

Alternative to ssh access though a cli: Putty and OpenSSH¶

Putty (Windows):

Known for its user-friendly GUI, Putty offers a straightforward interface for establishing SSH connections on Windows systems. It's particularly popular among users who prefer a graphical interface for SSH connections.

That's why Putty is a popular SSH client primarily used on Windows systems. However, it's worth noting that while Putty is predominantly associated with Windows, it can also be utilized on other operating systems through compatibility layers or third-party tools like Wine on Linux or macOS.

OpenSSH:

OpenSSH, on the other hand, is an open-source implementation of the SSH protocol. It's available not just for Windows but also for Linux, macOS, and various Unix-like operating systems. OpenSSH provides both the client (ssh) and server (sshd) components, making it a versatile and widely adopted solution for secure remote access, file transfer, and tunneling across different platforms. It offers a robust set of features, including secure remote access, file transfer (using tools like scp and sftp), and tunneling capabilities.

Thats's why OpenSSH is often preferred by users who work in mixed environments or want a consistent SSH experience across different operating systems. It's commonly used in command-line environments and scripts due to its versatile nature.

File Transfer Using SSH¶

You can use scp command to transfer files directly between two servers (local to remote or one remote to another) by specifying their addresses and file paths

Sending Files to Remote Server¶

Use the scp command:

local_file="/path/to/local/file"
remote_file="$remote_user@$remote_host:/path/to/remote/file/or/folder"
scp "$local_file" "$remote_file"

You'll be prompted for the password before the file is sent.

Transferring Between Servers¶

Similar to local to server transfer, use scp between two remote servers by specifying their addresses.

Use the scp command to transfer files directly between two remote servers:

```bash
remote_file_source="$remote_user1@$remote_host1:/path/to/source/file"
remote_file_destination="$remote_user2@$remote_host2:/path/to/destination/folder"
scp "$remote_file_source" "$remote_file_destination"
```

Replace: - $remote_user1 with the username for the first remote server. - $remote_host1 with the address or IP of the first remote server. - $remote_user2 with the username for the second remote server. - $remote_host2 with the address or IP of the second remote server.

This will transfer the specified file from the first remote server to the specified folder on the second remote server.

SCP Options¶

Using -r for recursive copying of directories:

scp -r local_directory username@remote_host:/remote_directory

Alternative File Transfer Methods¶

Using rsync for efficient synchronization:

rsync -avz --progress /path/to/source username@remote_host:/path/to/destination

Running commands on a remote server without accessing its cli¶

For example, using ssh to Fetch latest changes from the remote repository

ssh "$remote_user@$remote_host" "cd $remote_path && git fetch"

Simplifying SSH Access with sshpass¶

To avoid being prompted to write the password, sshpass is a tool you want

Install sshpass: If needed, install sshpass using sudo apt install sshpass.

Accessing SSH without Password Prompt: Instead of

ssh "$remote_user@$remote_host"

use

sshpass -p "$password" ssh "$remote_user@$remote_host"

to tetch latest changes from the remote repository, run

sshpass -p "$password" ssh "$remote_user@$remote_host" "cd $remote_path && git fetch"

Conclusion¶

Congratulations! You've now mastered the fundamentals of SSH connections and file transfers using Git Bash.

In this guide, we've covered the essential steps to initiate SSH connections, troubleshoot common errors, and conduct seamless file transfers between local and remote servers. You've learned to troubleshoot connection issues, enhance security configurations, and optimize file transfers using scp and rsync.

Remember, SSH is a powerful tool for secure communication and file transfer, and understanding its nuances empowers you to work efficiently across different servers and systems.

As you continue your journey, keep exploring the capabilities of SSH, experiment with different options and configurations, and don't hesitate to delve deeper into security best practices.

Whether you're a developer collaborating on remote repositories or a system administrator managing servers, the knowledge gained here will serve as a solid foundation for your endeavors.

Embrace the power of SSH, continue to explore, and may your future endeavors in remote access and file transfer be secure, efficient, and hassle-free!

Comprehensive Guide to SSH: Tunneling, File Transfers, and Key-Based Authentication