Rsync -a vs. Rsync -ax

Attribute	Rsync -a	Rsync -ax
Preserves permissions	Yes	Yes
Preserves timestamps	Yes	Yes
Preserves symbolic links	Yes	Yes
Preserves owner	Yes	Yes
Preserves group	Yes	Yes
Preserves devices	Yes	Yes
Preserves special files	Yes	Yes
Preserves hard links	Yes	Yes
Excludes ACLs	No	Yes
Excludes extended attributes	No	Yes

Introduction

Rsync is a powerful tool for synchronizing files and directories between two locations. It is widely used for backup and mirroring purposes due to its efficiency and flexibility. When using Rsync, users have the option to specify various options and flags to customize the behavior of the synchronization process. Two commonly used flags are -a and -ax, which have some key differences in their attributes.

Rsync -a

Rsync -a is a popular option that stands for "archive mode." When using the -a flag, Rsync preserves all the attributes of the files being synchronized, including permissions, timestamps, and ownership. This makes it ideal for creating exact replicas of the source directory at the destination. Additionally, the -a flag also enables recursive copying, meaning that it will synchronize all subdirectories and their contents.

Another important attribute of Rsync -a is that it preserves symbolic links during the synchronization process. This can be crucial when dealing with complex directory structures that rely on symbolic links to function properly. By using the -a flag, users can ensure that the integrity of their symbolic links is maintained across the synchronization.

One potential drawback of Rsync -a is that it does not preserve hard links by default. Hard links are multiple references to the same physical file on a filesystem, and preserving them can be important for certain use cases. However, users can overcome this limitation by combining the -a flag with the -H flag, which tells Rsync to preserve hard links during the synchronization process.

Rsync -ax

Rsync -ax is a variation of the -a flag that includes an additional attribute: the -x flag. The -x flag instructs Rsync to exclude directories from crossing filesystem boundaries during the synchronization process. This means that if the source directory contains symbolic links to directories on different filesystems, Rsync will not follow those links and synchronize the contents of the linked directories.

By using the -ax flag, users can prevent Rsync from inadvertently copying files and directories from external filesystems, which can help avoid potential issues with disk space and performance. This can be particularly useful when synchronizing large directory structures that span multiple filesystems, as it allows users to control the scope of the synchronization more effectively.

One important thing to note about Rsync -ax is that it may impact the completeness of the synchronization if there are symbolic links within the source directory that point to directories on different filesystems. In such cases, users may need to manually adjust their synchronization strategy to ensure that all necessary files and directories are included in the process.

Conclusion

In conclusion, both Rsync -a and Rsync -ax are valuable options for synchronizing files and directories, each with its own set of attributes and considerations. Rsync -a is ideal for creating exact replicas of the source directory, preserving all attributes and symbolic links. On the other hand, Rsync -ax adds the ability to exclude directories from crossing filesystem boundaries, providing more control over the synchronization process. Ultimately, the choice between Rsync -a and Rsync -ax will depend on the specific requirements of the synchronization task at hand.