Using rsync for data transfer and synchronization

Rsync is a data transport tool that can be used much like the scp command. When transferring data, rsync checks the difference between the source and target files and only transfers the parts that have changed. This makes rsync suitable for:

• Synchronizing folders. Using scp or cp would copy and transfer everything, while rsync will only copy and transfer the modifications.
• Transferring larger files. rsync can be set to save progress, so if the transfer is interrupted it can be resumed at the same point.

The Basic command syntax of rsync is:

rsync -options source target

If the data source or target location is a remote site, it is defined with syntax:

userame@server:/path/in/server

However, both the target and source can also be located on the same machine. In that case you can just give directory paths to source and target sites.

The table below lists the most commonly used options:

Option	Argument	Description
-r		recurse into directories
-a		Use archive mode: copy files and directories recursively and preserve access permissions and time stamps.
-v		Verbose mode.
-z		Compress
-e	ssh	Specify the remote shell to use.
-n		Show what files would be transferred.
--partial		Keep partially transferred files.
--progress		Show progress during transfer.
-P		same as --partial --progress

So the command for transferring a local folder to Puhti,while showing the progress and keeping partially transferred files, would be:

rsync -rP /path/to/local/folder  username@puhti.csc.fi:/path/to/target

This would either:

• create a folder on Puhti at /path/to/target/folder, if the folder was not present before. In this case, everything in the folder will be transferred
• synchronize the source and target folders, if the folder already exists on Puhti. In this case, only changes we have made will be transferred

And the same thing in reverse:

rsync -rP username@puhti.csc.fi:/path/to/target/folder /path/to/local

Note

rsync will always overwrite any changes made to the target, even if they are newer than the source.

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