Lines Matching +full:vs +full:- +full:n +full:- +full:supply
1 .. SPDX-License-Identifier: GPL-2.0
10 overlay-filesystem functionality in Linux (sometimes referred to as
11 union-filesystems). An overlay-filesystem tries to present a
17 ---------------
25 While directories will report an st_dev from the overlay-filesystem,
26 non-directory objects may report an st_dev from the lower filesystem or
29 over the lifetime of a non-directory object. Many applications and
48 The "xino" feature can be enabled with the "-o xino=on" overlay mount option.
51 the lifetime of the filesystem. The "-o xino=auto" overlay mount option
60 +--------------+------------+------------+-----------------+----------------+
65 +--------------+-----+------+-----+------+--------+--------+--------+-------+
68 +--------------+-----+------+-----+------+--------+--------+--------+-------+
69 | Layers not | N | N | Y | N | N | Y | N | Y |
72 +--------------+-----+------+-----+------+--------+--------+--------+-------+
74 +--------------+-----+------+-----+------+--------+--------+--------+-------+
75 | xino=on/auto,| N | N | Y | N | N | Y | N | Y |
77 +--------------+-----+------+-----+------+--------+--------+--------+-------+
84 ---------------
86 An overlay filesystem combines two filesystems - an 'upper' filesystem
106 A read-only overlay of two read-only filesystems may use any
110 -----------
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
123 mount -t overlay overlay -olowerdir=/lower,upperdir=/upper,\
141 --------------------------------
146 directories (non-directories are always opaque).
149 as a zero-size regular file with the xattr "trusted.overlay.whiteout".
167 -------
171 obvious way (upper is read first, then lower - entries that already
172 exist are not re-added). This merged name list is cached in the
186 - read part of a directory
187 - remember an offset, and close the directory
188 - re-open the directory some time later
189 - seek to the remembered offset
199 --------------------
220 - OVERLAY_FS_REDIRECT_DIR:
222 - OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW:
230 - "redirect_dir=BOOL":
232 - "redirect_always_follow=BOOL":
234 - "redirect_max=NUM":
239 - "redirect_dir=on":
241 - "redirect_dir=follow":
243 - "redirect_dir=nofollow":
245 - "redirect_dir=off":
263 Non-directories
264 ---------------
266 Objects that are not directories (files, symlinks, device-special
269 that requires write-access, such as opening for write access, changing
271 to the upper filesystem (copy_up). Note that creating a hard-link
276 opened for read-write but the data is not modified.
279 exists in the upper filesystem - creating it and any parents as
281 mode, mtime, symlink-target etc.) and then if the object is a file, the
287 filesystem - future operations on the file are barely noticed by the
293 ----------------
339 mount -t overlay overlay -olowerdir=/lower,upperdir=/upper,... /merged
343 cp -a /lower /upper
344 mount --bind /upper /merged
347 the time of copy (on-demand vs. up-front).
351 ---------------------
356 mount -t overlay overlay -olowerdir=/lower1:/lower2:/lower3 /merged
359 that case the overlay will be read-only.
368 mount -t overlay overlay -olowerdir=/a\:lower\:\:dir /merged
380 ---------------------
413 Data-only lower layers
414 ----------------------
429 as "data-only" lower layers, using double colon ("::") separators.
430 A normal lower layer is not allowed to be below a data-only layer, so single
436 mount -t overlay overlay -olowerdir=/l1:/l2:/l3::/do1::/do2 /merged
438 The paths of files in the "data-only" lower layers are not visible in the
440 in the "data-only" lower layers are not visible in overlayfs inodes.
442 Only the data of the files in the "data-only" lower layers may be visible
444 to the absolute path of the "lower data" file in the "data-only" lower layer.
447 least one data-only layer to enable redirection of data to a data-only layer.
448 In this case other forms of metacopy are rejected. Note: this way, data-only
453 Since kernel version v6.8, "data-only" lower layers can also be added using
465 --------------------------------------
481 fs-verity support
482 -----------------
485 fs-verity enabled and overlay verity support is enabled, then the
492 that was in the lower at the time of the copy-up. If at any time
496 digest check, or from a later read due to fs-verity) and a detailed
497 error is printed to the kernel logs. For more details of how fs-verity
504 layer is fully trusted (by using dm-verity or something similar), then
505 an untrusted lower layer can be used to supply validated file content
507 directories are specified as "Data-only", then they can only supply
514 - "off":
517 - "on":
522 - "require":
525 will only be used if the data file has fs-verity enabled,
526 otherwise a full copy-up is used.
529 --------------------------
569 ------------------------
585 alternative form of whiteout is supported. This form is a regular, zero-size
593 Non-standard behavior
594 ---------------------
604 b) If a file residing on a lower layer is opened for read-only and then
621 will fail with EXDEV ("Invalid cross-device link").
652 ---------------------------------
685 ----------
693 non-directory object, the index entry is a hard link to the upper inode.
701 1. For a non-upper object, encode a lower file handle from lower inode
703 3. For a pure-upper object and for an existing non-indexed upper object,
708 - Header including path type information (e.g. lower/upper)
709 - UUID of the underlying filesystem
710 - Underlying filesystem encoding of underlying inode
722 5. For a non-directory, instantiate a disconnected overlay dentry from the
727 Decoding a non-directory file handle may return a disconnected dentry.
744 The overlay filesystem does not support non-directory connectable file
753 read-write mount and will result in an error.
763 -------------
768 - "null":
770 - "off":
773 - "on":
778 - "auto": (default)
787 --------------
815 ----------
817 The "-o userxattr" mount option forces overlayfs to use the
823 ---------
828 https://github.com/amir73il/unionmount-testsuite.git
832 # cd unionmount-testsuite
833 # ./run --ov --verify