What Is Immutable Flag in Linux?

chattr (Change Attribute) is a command line Linux utility that is used to set/unset certain attributes to a file in Linux system to secure accidental deletion or modification of important files and folders, even though you are logged in as a root user. In Linux native filesystems i.e. ext2, ext3, ext4, btrfs, etc.

What is an immutable file?

An immutable file cannot be changed or renamed. An appendOnly file allows append operations, but not delete, modify, or rename operations. An immutable directory cannot be deleted or renamed, and files cannot be added or deleted under such a directory.

What does the immutable bit do to a file?

The chattr man page is clear on what happens when the immutable bit is set: A file with the ‘i’ attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file, most of the file’s metadata can not be modified, and the file can not be opened in write mode.