This script can be improved in various ways to enhance readability, safety, efficiency, and maintainability. I'll provide an improved version below with explanations. 

Key improvements: Use of functions: Encapsulating functionality in functions makes the code more readable and modular. 

Use of modern bash syntax: Using more modern bash syntax (e.g., $(...) for command substitution instead of backticks). 

Error handling: Adding error handling to make the script more robust in case of failure. 

Use of find instead of ls: ls is generally discouraged in scripts when manipulating filenames, as it can behave unexpectedly with certain special characters or spaces. 

Comments and logging: Improved comments and logging for clarity and better tracking of the script’s actions.

--------------------

Explanation of changes:

umask: Still in place to ensure the proper file permissions (022), allowing others to read the backup files.

Logging: A logging function (log_message) was added to centralize the logging logic and make it easier to track actions. All actions are now logged with timestamps.

Functionality split into functions:

remove_faulty_dumps(): Handles removal of SQL dump files smaller than 10K.

cleanup_multiple_copies(): Handles cleanup of redundant .sql.bz2 files, keeping only the most recent $KEEP_RECENT backups.

purge_older_files(): A placeholder function where you can add more complex retention policies (e.g., keeping files for different date ranges as mentioned in the comments).

find and xargs: Replaced ls with find for robustness when dealing with file names. This also avoids issues with special characters, spaces, or other quirks that ls might not handle well in scripts. xargs -0 and find -print0 are used for safe file handling.

Error handling: Added error handling when changing directories (cd) to ensure the script exits if it cannot access the archive directory.

Modularization: By splitting the script into functions, it’s easier to maintain and extend. For example, adding new retention logic can be done easily within purge_older_files().

To customize:

The retention policy (e.g., number of backups to keep, or how to handle older backups) can be expanded within purge_older_files().

The $KEEP_RECENT variable can be adjusted if you want to keep more or fewer recent backups.

This version is more maintainable, secure, and easier to extend in the future.
