scp Command Summary

What is the scp Command?

It’s for transferring files…

When we use ssh to operate a server and need to transfer files to it, the scp command transfers files through the ssh port.

Usage

When we type scp in the terminal, we get this:

weepingdogel@WeepingDogel ~> scp
usage: scp [-346BCpqrTv] [-c cipher] [-F ssh_config] [-i identity_file]
            [-J destination] [-l limit] [-o ssh_option] [-P port]
            [-S program] source ... target

We quickly recognize some parameters…

Examples

Let me give some examples to demonstrate the specific usage…

First, let me describe my test environment:

Arch Linux

IP: 192.168.0.105

CentOS8 VM

IP: 192.168.0.108

Uploading a File

$ scp [local filename] username@address:[filename]

This is the general usage, but make sure the path is correct!

For example:

weepingdogel@WeepingDogel ~ [1]> scp ./compile/7.1.0.zip [email protected]:/root/
[email protected]'s password: 
7.1.0.zip                                                    100%   95KB   5.2MB/s   00:00 

That’s simple — nothing more to say…

Downloading a File

What if we need to download a file from the server to modify it, and the server doesn’t have ftp?

We need to use SSH to find the file’s location, but I won’t go into detail about that — it’s off-topic. (Just know the file’s location.)

$ scp username@address:[filename] [local filename]

Reminder: this filename is a path!

It’s a relative path or absolute path! It depends on the situation, but it’s definitely a path!

For example:

weepingdogel@WeepingDogel ~> scp [email protected]:/root/index.html /tmp/index.html
[email protected]'s password: 
index.html                                                   100%   46KB 728.6KB/s   00:00
weepingdogel@WeepingDogel ~> ls /tmp/*.html -lh
-rw-r--r-- 1 weepingdogel weepingdogel 47K  Sep  5 20:54 /tmp/index.html

You just need to know the exact location of the file on the server and decide where to save it locally.

Specifying a Port

Generally, SSH uses port 22, which is the case for cloud servers or servers with public IPs.

But the examples above are based on local network file transfers. We need NAT traversal for remote file transfers, which typically assigns a different port for SSH to establish a tunnel, so the port is no longer 22.

I use SakuraFRP — a very useful free NAT traversal service!

Upload:

scp -P [port] [local filename] username@address:[filename]

Download:

scp -P [port] username@address:[filename] [local filename]

I’ve already reminded you many times that this [filename] is a path. No more repetition here.

Well… here’s how it looks:

weepingdogel@WeepingDogel ~> scp -P 45820 [email protected]:/root/test.py /tmp/test.py

But let me do a combined command:

weepingdogel@WeepingDogel ~ [1]> scp -P 45820 [email protected]:/root/test.py /tmp/test.py && cd /tmp && python test.py
The authenticity of host '[cn-zj-dx-2.sakurafrp.com]:45820 ([222.186.174.33]:45820)' can't be established.
ECDSA key fingerprint is SHA256:8J1Z+I8NtPXAk7EFDwLiwu8pmwSoPLYeJM2iYnV7z5M.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '[cn-zj-dx-2.sakurafrp.com]:45820,[222.186.174.33]:45820' (ECDSA) to the list of known hosts.
[email protected]'s password: 
test.py                                                      100%   21     0.2KB/s   00:00    
Hello World

Uploading is pretty much the same — just reverse the order. I won’t demonstrate it here.

Done writing!

Reference Links

What? None this time. I figured it out myself…

Well, to be accurate, there is one — search engines~