chattr.1: document the verity attribute

Document the verity file attribute ('V').

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/chattr.1.in b/misc/chattr.1.in
index 1c9e896..2122a13 100644 (file)
--- a/misc/chattr.1.in
+++ b/misc/chattr.1.in
@@ -52,7 +52,8 @@ The following attributes are read-only, and may be listed by
 but not modified by chattr:
 encrypted (E),
 indexed directory (I),
-and inline data (N).
+inline data (N),
+and verity (V).
 .PP
 Not all flags are supported or utilized by all filesystems; refer to
 filesystem-specific man pages such as
@@ -189,6 +190,15 @@ saved.  This allows the user to ask for its undeletion.  Note: please
 make sure to read the bugs and limitations section at the end of this
 document.
 .PP
+A file with the 'V' attribute set has fs-verity enabled.  It cannot be
+written to, and the filesystem will automatically verify all data read
+from it against a cryptographic hash that covers the entire file's
+contents, e.g. via a Merkle tree.  This makes it possible to efficiently
+authenticate the file.  This attribute may not be set or reset using
+.BR chattr (1),
+although it can be displayed by
+.BR lsattr (1).
+.PP
 .SH AUTHOR
 .B chattr
 was written by Remy Card <Remy.Card@linux.org>.  It is currently being