[Linux Cheat Sheet] Copying Files to a Remote Host
I recently moved my portfolio from my old UC Irvine server to my new one at www.jaytolentino.com, and so ran into copying my local files to a remote host. I've had to use these commands several times whenever I'm moving things around, so I thought it would be fitting to have it on my blog. Plus, I'll tag this and any similar future posts with Linux Cheat Sheet for any commands I want to remember.
Anyways, there are two commands one can use to move files over, and the one you choose depends on what you're copying.
Secure Copy
command: scp
usage: to copy one or multiple files securely over a network
syntax:
scp [OPTIONS] /path/to/source user@host:/path/to/destination
useful options:
-r, --recursive (recursively copies directories)
scp Example: copying everything in my current directory to my remote host's public directory:
scp -r . [email protected]:~/public_html/
Rsync
command: rsync
usage: allows copying of only modified or new files
syntax:
rsync [OPTIONS] /path/to/source user@host:/path/to/destination
useful options:
-r, --recursive (recursively copies directories)
-u, --update (only copy new files or updated files)
--delete (deletes remote files that don't exist in source directory)
rsync Example: copying everything in my current directory to my remote host's public directory:
rsync -ru --delete . [email protected]:~/public_html/
So the story goes that, after making my initial move from local to remote, I ended up changing some files. But if I kept using scp, then every file would be recopied to the remote host, even ones I didn't change. As the number of files grew, so did the time it took to transfer things over. After a quick search, I discovered rsync solved this problem for me.
Another problem I ran into with scp is that I couldn't "copy over" files that I deleted. I would then go into my remote host and manually delete them from there. But! rsync solves that problem when you include that handy --delete flag.
Securing rsync
I'm sure you're wondering "Well, is rsync secure?" Answer: if you use it in conjunction with SSH, then yes. For more on SSH and rsync you can check out "Securing automated rysync over SSH"[1]. And if you want to combine this with cron jobs (which is a tool for automating jobs based on some schedule, e.g. copying files to a remote host at 5AM daily), you can check out "Using Rsync and SSH: Keys, Validating, and Automation" [3].
Alright, so here's the breakdown...
Use scp when:
copying individual or multiple files once
you want no-fuss security
copying only modified or new files
deleting files on remote that were deleted locally
doing automated jobs, but as long as you secure it with SSH
Lastly, if you're really curious about how SCP works behind-the-scenes, take a look at "How the SCP protocol works" by Jan Pechanec. Thanks and hoped this helped you guys as much as it helped me!
Notes:
There also exists the rcp command which functions similarly to scp. However, as you might realize from the name, scp secures files transferred over the network using encryption since it's based on the ssh protocol. See [2]
Resources & Further Reading:
[1] "Securing automated rsync over SSH" by Stephanie Kattoor (2008)
[2] "rcp, scp, ftp - Comands for Copying Files Between Computers" by Juergen Haas (2008)
[3] "Using Rsync and SSH: Keys, Validating, and Automation" by Troy Johnson (2013)
[4] "How the SCP protocol works" by Jan Pechanec, Oracle (2007)
[5] Full list of scp options
[6] Full list of rsync options
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