Using Rsync to Copy Only Files that Have Changed

Oct 13, 2025 by talynt.org 46 views

Introduction

Rsync is a powerful command-line utility that allows you to efficiently copy and synchronize files and directories between two locations. One of its key features is its ability to copy only files that have changed, rather than transferring all files every time. This makes it an ideal tool for backing up data, synchronizing files between multiple machines, and mirroring directories. In this article, we will explore how to use rsync to copy only files that have changed, not files that are new.

Understanding Rsync

Before we dive into the specifics of using rsync to copy only files that have changed, let's take a brief look at how rsync works. Rsync uses a combination of algorithms and techniques to determine which files have changed and need to be transferred. Here are some of the key concepts that underlie rsync's functionality:

Checksums: Rsync uses checksums to identify files and determine whether they have changed. A checksum is a unique numerical value that is calculated based on the contents of a file.
Delta encoding: Rsync uses delta encoding to represent the differences between two files. This allows it to transfer only the changes, rather than the entire file.
Incremental updates: Rsync can perform incremental updates, which means that it only transfers the files that have changed since the last update.

Using Rsync to Copy Only Files that Have Changed

Now that we have a basic understanding of how rsync works, let's take a look at how to use it to copy only files that have changed. The basic syntax for using rsync is as follows:

rsync -avz source/ dest/

Here's a breakdown of the options used in this command:

-a: This option tells rsync to archive mode, which means that it will preserve file permissions, ownership, and timestamps.
-v: This option tells rsync to be verbose, which means that it will display detailed information about the files being transferred.
-z: This option tells rsync to compress the data being transferred, which can help to reduce the amount of data that needs to be transferred.
source/: This is the source directory that you want to copy from.
dest/: This is the destination directory that you want to copy to.

However, if you want to copy only files that have changed, not files that are new, you need to use the --update option. Here's an example of how to use this option:

rsync -avz --update source/ dest/

This will copy only the files that have changed since the last update, rather than transferring all files.

Using Rsync with the `--delete` Option

Another useful option when using rsync is the --delete option. This option tells rsync to delete any files in the destination directory that are not present in the source directory. This can be useful if you want to ensure that the destination directory is always up-to-date with the source directory.

Here's an example of how to use the --delete option:

rsync -avz --update --delete source/ dest/

This will copy only the files that have changed since the last update, and delete any files in the destination directory that are not present in the source directory.

Using Rsync with the `--exclude` Option

If you want to exclude certain files or directories from the transfer, you can use the --exclude option. This option allows you to specify a pattern that matches the files or directories that you want to exclude.

Here's an example of how to use the --exclude option:

rsync -avz --update --exclude '*.tmp' source/ dest/

This will copy only the files that have changed since the last update, and exclude any files with the .tmp extension.

Conclusion

In this article, we have explored how to use rsync to copy only files that have changed, not files that are new. We have looked at the basic syntax for using rsync, and discussed some of the key options that you can use to customize the transfer. We have also looked at how to use the --update option to copy only files that have changed, and how to use the --delete option to delete any files in the destination directory that are not present in the source directory. Finally, we have looked at how to use the --exclude option to exclude certain files or directories from the transfer.

Best Practices for Using Rsync

Here are some best practices to keep in mind when using rsync:

Use the --update option: This option tells rsync to copy only files that have changed since the last update.
Use the --delete option: This option tells rsync to delete any files in the destination directory that are not present in the source directory.
Use the --exclude option: This option allows you to specify a pattern that matches the files or directories that you want to exclude.
Use the --verbose option: This option tells rsync to display detailed information about the files being transferred.
Use the --compress option: This option tells rsync to compress the data being transferred, which can help to reduce the amount of data that needs to be transferred.

Common Rsync Commands

Here are some common rsync commands that you may find useful:

rsync -avz source/ dest/: This command copies all files from the source directory to the destination directory.
rsync -avz --update source/ dest/: This command copies only files that have changed since the last update.
rsync -avz --delete source/ dest/: This command copies only files that have changed since the last update, and deletes any files in the destination directory that are not present in the source directory.
rsync -avz --exclude '*.tmp' source/ dest/: This command copies only files that have changed since the last update, and excludes any files with the .tmp extension.

Troubleshooting Rsync

Here are some common issues that you may encounter when using rsync, along with some tips for troubleshooting:

Error: "rsync: connection refused": This error occurs when the destination machine is not responding to the rsync connection. Try restarting the rsync service on the destination machine.
Error: "rsync: permission denied": This error occurs when you do not have permission to access the source or destination directory. Try running the command with elevated privileges.
Error: "rsync: file not found": This error occurs when the file or directory specified in the command does not exist. Try checking the file or directory path to ensure that it is correct.

Conclusion

Introduction

Rsync is a powerful command-line utility that allows you to efficiently copy and synchronize files and directories between two locations. In this article, we will answer some of the most frequently asked questions about rsync, covering topics such as basic usage, options, and troubleshooting.

Q: What is rsync?

A: Rsync is a command-line utility that allows you to efficiently copy and synchronize files and directories between two locations. It uses a combination of algorithms and techniques to determine which files have changed and need to be transferred.

Q: How do I use rsync?

A: The basic syntax for using rsync is as follows:

rsync -avz source/ dest/

Here's a breakdown of the options used in this command:

-a: This option tells rsync to archive mode, which means that it will preserve file permissions, ownership, and timestamps.
-v: This option tells rsync to be verbose, which means that it will display detailed information about the files being transferred.
-z: This option tells rsync to compress the data being transferred, which can help to reduce the amount of data that needs to be transferred.
source/: This is the source directory that you want to copy from.
dest/: This is the destination directory that you want to copy to.

Q: What are the most common rsync options?

A: Some of the most common rsync options include:

-a: Archive mode, which preserves file permissions, ownership, and timestamps.
-v: Verbose mode, which displays detailed information about the files being transferred.
-z: Compress the data being transferred, which can help to reduce the amount of data that needs to be transferred.
--update: Copy only files that have changed since the last update.
--delete: Delete any files in the destination directory that are not present in the source directory.
--exclude: Exclude certain files or directories from the transfer.

Q: How do I exclude certain files or directories from the transfer?

A: You can use the --exclude option to exclude certain files or directories from the transfer. For example:

rsync -avz --exclude '*.tmp' source/ dest/

This will exclude any files with the .tmp extension from the transfer.

Q: How do I delete any files in the destination directory that are not present in the source directory?

A: You can use the --delete option to delete any files in the destination directory that are not present in the source directory. For example:

rsync -avz --delete source/ dest/

Q: How do I copy only files that have changed since the last update?

A: You can use the --update option to copy only files that have changed since the last update. For example:

rsync -avz --update source/ dest/

Q: What are some common rsync errors and how do I troubleshoot them?

A: Some common rsync errors include:

rsync: connection refused: This error occurs when the destination machine is not responding to the rsync connection. Try restarting the rsync service on the destination machine.
rsync: permission denied: This error occurs when you do not have permission to access the source or destination directory. Try running the command with elevated privileges.
rsync: file not found: This error occurs when the file or directory specified in the command does not exist. Try checking the file or directory path to ensure that it is correct.

Q: How do I use rsync with a remote server?

A: You can use rsync with a remote server by specifying the remote server's hostname or IP address in the source or dest path. For example:

rsync -avz source/ user@remote-server:/dest/

This will copy the files from the source directory to the dest directory on the remote server.

Q: How do I use rsync with a local directory?

A: You can use rsync with a local directory by specifying the local directory path in the source or dest path. For example:

rsync -avz source/ /local/directory/

This will copy the files from the source directory to the local/directory directory on the local machine.

Conclusion

In this article, we have answered some of the most frequently asked questions about rsync, covering topics such as basic usage, options, and troubleshooting. We hope that this article has been helpful in answering your questions about rsync and has provided you with a better understanding of how to use this powerful command-line utility.