Looking for an application to sync SFTP to local

I'm looking for an application that would dynamically sync an external SFTP site to local storage. So whenever a file changes ( including new file or delete file ), the local side reflects that ( within some interval ).

I suppose it might be necessary for this app to exist on both sides. Perhaps it's a special type of SFTP server.

Also interested in cloud solutions.

But reality today is that many traditional DC SFTP servers exist and the providers don't offer much flexibility ( e.g. they use a specific SFTP product and won't change ).

Ftp Voyager will do this. (Assuming windows, you did not say) https://thwack.solarwinds.com/resources/b/geek-speak/posts/ftp-voyager-debuts-as-solarwinds-free-tool

It will install as a service, and has a scheduler to make connection profiles to sites and then schedule them pull down data at times/intervals.

It is not hard to script SFTPs native client either, or even PSFTP (Part of the putty project), very similar syntax if you are familiar with ftp commands. https://www.puttygen.com/psftp

Specifically the switch -B, with with you can basically process a script of commands to do just like you were at the terminal, and then make that a task in the task scheduler

-B – It specifies a file with batch commands. The ‘-b’ command helps user automate tasks by allowing them to set commands in advance.

Syncing SFTP this way in either case does not require the server side to even be aware yo are automating it, much less install anything, It simply does the same thing a user would via code. https://the.earth.li/~sgtatham/putty/0.52/htmldoc/Chapter6.html

Example using psftp: make a simple text file named dlall.txt

assuming there is an in queue folder named iQ, and a directory on the other side named out, the following script...

lcd - Change local directory to iQ

cd out - changes to out directory on remote side

mget * - multiple file get, downloads what is there.

quit - exits

lcd .\iQ
cd out
mget *
quit

and then pass it to PSFTP like so

psftp user@host -P [port number] -b dlall.txt

Now this assumes you know how to do authentication, both will accept credentials on the command line or you can set up pubkey authentication. I do not suggest password, because to automate it you have to store a password somewhere in plain text. FtpVoyager will store passwords but at least encrypt them. Both will work with pubkey much safer though.

Note as well you used the word "sync" if you want to make sure both sides are actually equal, this is harder, and woudl likely steeer you back to FTPVoyager

https://support.solarwinds.com/SuccessCenter/s/article/How-Can-FTP-Voyager-Automatically-Synchronize-Folders-on-2-Different-Sites?language=en_US

OR possibly look into rsync over ssh if the server will support that.