🔐 Linux/Unix: Transfers & Access – ssh, scp, rsync, sftp Explained with Examples

🧲 Introduction – Why Learn Secure Transfers & Access in Linux?

In Linux and Unix systems, remote access and file transfers are essential for system administration, backups, scripting, and DevOps. Tools like ssh, scp, rsync, and sftp enable you to connect securely, transfer data, and synchronize files over networks—all encrypted via SSH.

🎯 In this guide, you’ll learn:

• How to securely connect to remote machines using ssh
• How to transfer files with scp, rsync, and sftp
• The differences, use cases, and output of each tool

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🔑 1. ssh – Secure Remote Shell Access

✅ What is ssh?

ssh (Secure Shell) allows you to log in to remote systems securely over an encrypted channel.

🛠️ Syntax:

ssh [user@]hostname [command]

🧪 Example 1: Login to a remote machine

ssh user@192.168.1.100

📤 Output:

user@192.168.1.100's password:
Welcome to Ubuntu 22.04 LTS ...

🧪 Example 2: Run a command remotely

ssh user@192.168.1.100 uptime

📤 Output:

 14:23:01 up 10 days,  5:12,  2 users,  load average: 0.15, 0.09, 0.05

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📤 2. scp – Secure Copy Over SSH

✅ What is scp?

scp securely transfers files between local and remote systems using SSH.

🛠️ Syntax:

scp [options] source destination

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🧪 Example 1: Copy a file to remote server

scp file.txt user@192.168.1.100:/home/user/

🧪 Example 2: Copy a remote file to local system

scp user@192.168.1.100:/var/log/syslog /tmp/

🧠 Common Flags:

Flag	Description
-r	Recursive copy (for dirs)
-P	Use custom port
-v	Verbose output

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🔁 3. rsync – Efficient Synchronization Tool

✅ What is rsync?

rsync is used to synchronize files and directories between local and remote systems. It transfers only differences, making it fast and efficient.

🛠️ Syntax:

rsync [options] source destination

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🧪 Example 1: Sync local directory to remote

rsync -avz /etc/ user@192.168.1.100:/backup/etc/

📤 Output:

sending incremental file list
etc/
etc/passwd
etc/hostname
sent 4,095 bytes  received 82 bytes  total size 3,512

🧠 Common Flags:

Flag	Description
-a	Archive (preserve all)
-v	Verbose
-z	Compress during transfer
--delete	Delete extra files on dest

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🌐 4. sftp – Interactive File Transfer over SSH

✅ What is sftp?

sftp provides an interactive shell to transfer files using the SSH File Transfer Protocol.

🛠️ Syntax:

sftp [user@]host

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🧪 Example 1: Start SFTP session

sftp user@192.168.1.100

📤 Output:

Connected to 192.168.1.100.
sftp>

🧪 Example 2: Upload and download files

Inside sftp> shell:

put localfile.txt
get remotefile.log

🧠 Common SFTP Commands:

Command	Description
ls	List remote files
lcd	Change local dir
cd	Change remote dir
put	Upload file
get	Download file
exit	Exit sftp shell

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⚖️ Comparison Table: ssh vs scp vs rsync vs sftp

Tool	Purpose	Supports SSH	Interactivity	Best For
ssh	Remote command execution	✅	❌	Login and shell commands
scp	Secure file copy	✅	❌	Simple file transfers
rsync	Efficient file synchronization	✅	❌	Backups and incremental syncs
sftp	Interactive file transfers	✅	✅	Manual uploads/downloads

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📌 Summary – Recap & Next Steps

These Linux tools make it easy to remotely access systems, transfer files securely, and sync data across environments. They’re built on SSH, ensuring encrypted communication.

🔍 Key Takeaways:

• Use ssh to log into remote systems or run remote commands
• Use scp for quick file copying over SSH
• Use rsync for efficient, repeatable file backups and sync
• Use sftp for interactive file uploads/downloads

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❓ FAQs

❓ Is scp faster than rsync?
❌ No. rsync is faster for large or repeat transfers due to delta-copying.

❓ Can I resume interrupted scp transfers?
❌ Not natively. Use rsync instead:

rsync --partial --progress file user@host:/path/

❓ How can I change ports in ssh, scp, or rsync?
✅ Use -p for ssh/scp, and -e 'ssh -p PORT' for rsync.

❓ Which one supports GUI alternatives?
✅ sftp can be used via GUI tools like FileZilla, WinSCP, or Cyberduck.

❓ Is it secure to use these tools over the internet?
✅ Yes, if using SSH keys and disabling password authentication for added security.

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