Lines Matching full:lower
26 non-directory objects may report an st_dev from the lower filesystem or
83 Upper and Lower
87 and a 'lower' filesystem. When a name exists in both filesystems, the
89 'lower' filesystem is either hidden or, in the case of directories,
92 It would be more correct to refer to an upper and lower 'directory
96 lower.
98 A wide range of filesystems supported by Linux can be the lower filesystem,
100 needed for OverlayFS to work. The lower filesystem does not need to be
101 writable. The lower filesystem can even be another overlayfs. The upper
113 upper and lower filesystems and refers to a non-directory in either,
114 then the lower object is hidden - the name refers only to the upper
117 Where both upper and lower objects are directories, a merged directory
123 mount -t overlay overlay -olowerdir=/lower,upperdir=/upper,\
134 exists, else the lower.
138 directory only. These attributes of the lower directory are hidden.
143 In order to support rm and rmdir without changing the lower
152 matching name in the lower level is ignored, and the whiteout itself
157 directory in the lower filesystem with the same name is ignored.
170 lower directories are each read and the name lists merged in the
171 obvious way (upper is read first, then lower - entries that already
196 underlying directory (upper or lower).
201 When renaming a directory that is on the lower layer or merged (i.e. the
250 indexed by the file handle of the lower inode and a file handle of the
255 lower directory. In that case, lookup returns an error and warns about
258 Because lower layer redirects cannot be verified with the index, enabling
267 files etc.) are presented either from the upper or lower filesystem as
268 appropriate. When a file in the lower filesystem is accessed in a way
270 some metadata etc., the file is first copied from the lower filesystem
282 data is copied from the lower to the upper filesystem. Finally any
302 compared to direct access on underlying lower or upper filesystems
309 b) check if mounting task would be allowed real operation on lower or
325 mount -t overlay overlay -olowerdir=/lower,upperdir=/upper,... /merged
329 cp -a /lower /upper
336 Multiple lower layers
339 Multiple lower layers can now be given using the colon (":") as a
347 The specified lower directories will be stacked beginning from the
351 Note: directory names containing colons can be provided as lower layer by
354 mount -t overlay overlay -olowerdir=/a\:lower\:\:dir /merged
357 be configured as lower layer using the "lowerdir+" mount options and the
360 fsconfig(fs_fd, FSCONFIG_SET_STRING, "lowerdir+", "/a:lower::dir", 0);
362 In the latter case, colons in lower layer directory names will be escaped
373 WRITE operation. After the lower file's data is copied up,
385 Do not use metacopy=on with untrusted upper/lower directories. Otherwise
387 appropriate REDIRECT and METACOPY xattrs, and gain access to file on lower
399 Data-only lower layers
407 2) st_ino and st_dev object identifier from a file in a lower layer
409 3) data from a file in another lower layer (further below)
411 The "lower data" file can be on any lower layer, except from the top most
412 lower layer.
414 Below the top most lower layer, any number of lower most layers may be defined
415 as "data-only" lower layers, using double colon ("::") separators.
416 A normal lower layer is not allowed to be below a data-only layer, so single
424 The paths of files in the "data-only" lower layers are not visible in the
426 in the "data-only" lower layers are not visible in overlayfs inodes.
428 Only the data of the files in the "data-only" lower layers may be visible
429 when a "metacopy" file in one of the lower layers above it, has a "redirect"
430 to the absolute path of the "lower data" file in the "data-only" lower layer.
432 Since kernel version v6.8, "data-only" lower layers can also be added using
463 During metadata copy up of a lower file, if the source file has
465 digest of the lower file is added to the "trusted.overlay.metacopy"
466 xattr. This is then used to verify the content of the lower file
471 that was in the lower at the time of the copy-up. If at any time
472 (during a mount, after a remount, etc) such a file in the lower is
484 an untrusted lower layer can be used to supply validated file content
485 for all metacopy files. If additionally the untrusted lower
510 Lower layers may be shared among several overlay mounts and that is indeed
511 a very common practice. An overlay mount may use the same lower layer
512 path as another overlay mount and it may use a lower layer path that is
513 beneath or above the path of another overlay lower layer path.
524 different lower layer path, is allowed, unless the "index" or "metacopy"
528 handle of the lower layer root directory, along with the UUID of the lower
531 the lower root directory file handle and lower filesystem UUID are compared
533 lower root origin, mount will fail with ESTALE. An overlayfs mount with
534 "index" enabled will fail with EOPNOTSUPP if the lower filesystem
535 does not support NFS export, lower filesystem does not have a valid UUID or
539 mount time. So if same upper is mounted with different set of lower, mount
545 the copied layers will fail the verification of the lower root file handle.
550 It is possible to use a lower directory that is stored on an overlayfs
558 in the lower dir will be exposed as a regular file with a
562 A lower dir with a regular whiteout will always be handled by the overlayfs
568 userspace tools (like containers) that generate lower layers.
581 done in the case when the file resides on a lower layer.
583 b) If a file residing on a lower layer is opened for read-only and then
587 c) If a file residing on a lower layer is being executed, then opening that
599 If this feature is disabled, then rename(2) on a lower or merged directory
639 upper tree. Offline changes to the lower tree are only allowed if the
641 have not been used. If the lower tree is modified and any of these
646 behavior on offline changes of the underlying lower layer is different
649 On every copy_up, an NFS file handle of the lower inode, along with the
650 UUID of the lower filesystem, are encoded and stored in an extended
654 that found a lower directory at the lookup path or at the path pointed
656 that the found lower directory file handle and lower filesystem UUID
658 found lower directory does not match the stored origin, that directory
669 With the "nfs_export" feature, on copy_up of any lower object, an index
680 1. For a non-upper object, encode a lower file handle from lower inode
681 2. For an indexed object, encode a lower file handle from copy_up origin
687 - Header including path type information (e.g. lower/upper)
698 3. For a lower file handle, lookup the handle in index directory by name.
710 When overlay filesystem has multiple lower layers, a middle layer
711 directory may have a "redirect" to lower directory. Because middle layer
712 "redirects" are not indexed, a lower file handle that was encoded from the
714 layer directory. Similarly, a lower file handle that was encoded from a
717 directories that cannot be decoded from a lower file handle, these
737 is changed. This is only applicable if all lower/upper/work directories are on