How to Make rsync Update Files Transferred in Previous Executions

rsync is a powerful tool for synchronizing files and directories between different locations. It is commonly used in backup scenarios or when transferring files over a network. By default, rsync only transfers files that are new or have been modified since the last execution. However, there may be situations where you want rsync to update files that were transferred in previous executions. In this article, we will explore how to achieve this.

Understanding rsync

Before we dive into updating transferred files, let's briefly understand how rsync works. rsync compares the source and destination files and transfers only the differences between them. This makes it efficient and fast, especially when dealing with large files or directories.

By default, rsync uses the modification time and file size to determine if a file needs to be transferred. If the modification time or file size is different in the source and destination, rsync considers the file as changed and transfers it. However, this approach does not consider the content of the files.

Using rsync's --checksum Option

To make rsync update files transferred in previous executions, we can use the --checksum option. This option tells rsync to compare the checksums of the source and destination files, rather than just the modification time and file size.

When the --checksum option is used, rsync calculates a checksum for each file on both the source and destination. It then compares these checksums to determine if the file needs to be transferred. If the checksums are different, rsync transfers the file.

Using the --checksum option ensures that rsync updates transferred files even if their modification time or file size remains the same. However, it comes at the cost of increased processing time, as rsync needs to calculate the checksums for all files.

To use the --checksum option, simply include it in your rsync command. For example:

This command will synchronize the source_directory with the destination_directory, updating any transferred files that have different checksums.

Using rsync's --update Option

Another option to make rsync update transferred files is the --update option. This option tells rsync to skip any files on the destination that are newer than the files on the source.

By default, rsync transfers all files from the source to the destination. However, when the --update option is used, rsync compares the modification times of the source and destination files. If the file on the destination is newer, rsync skips transferring it.

Using the --update option ensures that rsync updates transferred files only if the source file is newer. This can be useful when you want to avoid overwriting newer files on the destination.

To use the --update option, include it in your rsync command. For example:

This command will synchronize the source_directory with the destination_directory, updating any transferred files that are older on the destination.

Combining --checksum and --update

In some cases, you may want to combine the --checksum and --update options to ensure that rsync updates transferred files based on both the checksum and modification time. This can be useful when dealing with files that have the same modification time, but different content.

To combine these options, include both of them in your rsync command. For example:

This command will synchronize the source_directory with the destination_directory, updating any transferred files that have different checksums or are older on the destination.

Conclusion

rsync is a versatile tool for synchronizing files and directories. By default, it transfers only new or modified files. However, using the --checksum and --update options, you can make rsync update files transferred in previous executions based on their content and modification time.

References

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