The existing cpio extraction logic reads (maximum PATH_MAX) name_len
bytes from the archive into the collected name buffer and ensures that
the trailing byte is a null-terminator. This allows the actual file name
to be shorter than name_len, with the name string simply zero-terminated
prior to the last byte.
Initramfs generators, such as dracut-cpio[1], can take advantage of name
zero-padding to align file data segments within the archive to
filesystem block boundaries. Block boundary alignment may allow the
copy_file_range syscall to reflink archive source and destination
extents.
Link: 300e4b116c [1]
Signed-off-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://lore.kernel.org/r/20250819032607.28727-7-ddiss@suse.de
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Update the document to reflect that initramfs didn't replace initrd
following kernel 2.5.x.
The initramfs buffer format now supports many compression types in
addition to gzip, so include them in the grammar section.
c_mtime use is dependent on CONFIG_INITRAMFS_PRESERVE_MTIME.
Signed-off-by: David Disseldorp <ddiss@suse.de>
Link: https://lore.kernel.org/r/20250402033949.852-2-ddiss@suse.de
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
