The Linux operating system implements a POSIX standard interfaces and API with additional interfaces. Many of them have become common in other filesystems. The ones listed below have been added relatively recently and are considered interesting for users:
- birth/origin inode time
- a timestamp associated with an inode of when it was created, cannot be changed and requires the statx syscall to be read
- statx
- an extended version of the stat syscall that provides extensible interface to read more information that are not available in original stat
- fallocate modes
the fallocate syscall allows to manipulate file extents
Supported modes:
- keep size (FALLOC_FL_KEEP_SIZE)
- hole punching (FALLOC_FL_PUNCH_HOLE)
- zero range (FALLOC_FL_ZERO_RANGE)
- FIEMAP
- an ioctl that enumerates file extents, related tool is :command:`filefrag`
- filesystem label
- another filesystem identification, could be used for mount or for better recognition, can be set or read by an ioctl or by command :ref:`btrfs filesystem label<man-filesystem-label>`
- O_TMPFILE
- mode of open() syscall that creates a file with no associated directory entry, which makes it impossible to be seen by other processes and is thus safe to be used as a temporary file (https://lwn.net/Articles/619146/)
- xattr, acl
- extended attributes (xattr) is a list of key=value pairs associated with a file, usually storing additional metadata related to security, access control list in particular (ACL) or properties (:doc:`btrfs-property`)
- cross-rename
- mode of renameat2 syscall that can atomically swap 2 directory entries (files/directories/subvolumes/symlinks) within the same filesystem