chattr — Change attributes of files or directories. More information: <https://manned.org/chattr>.

Make a file or directory [i]mmutable to changes and deletion, even by superuser

sudo chattr +i {{path/to/file_or_directory}}

Make a file or directory mutable

sudo chattr -i {{path/to/file_or_directory}}

[R]ecursively make an entire directory and contents immutable

sudo chattr -R +i {{path/to/directory}}

Mark a directory and its files to be interpreted in a case-insensitive manner (case-[F]olding)

chattr +F {{path/to/directory}}

Set a file to only allow [a]ppending

sudo chattr +a {{path/to/file}}