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a907c907 N |
1 | Written by: Neil Brown |
2 | Please see MAINTAINERS file for where to send questions. | |
7c37fbda NB |
3 | |
4 | Overlay Filesystem | |
5 | ================== | |
6 | ||
7 | This document describes a prototype for a new approach to providing | |
8 | overlay-filesystem functionality in Linux (sometimes referred to as | |
9 | union-filesystems). An overlay-filesystem tries to present a | |
10 | filesystem which is the result over overlaying one filesystem on top | |
11 | of the other. | |
12 | ||
16149013 AG |
13 | |
14 | Overlay objects | |
15 | --------------- | |
16 | ||
17 | The overlay filesystem approach is 'hybrid', because the objects that | |
18 | appear in the filesystem do not always appear to belong to that filesystem. | |
19 | In many cases, an object accessed in the union will be indistinguishable | |
7c37fbda NB |
20 | from accessing the corresponding object from the original filesystem. |
21 | This is most obvious from the 'st_dev' field returned by stat(2). | |
22 | ||
23 | While directories will report an st_dev from the overlay-filesystem, | |
65f26738 | 24 | non-directory objects may report an st_dev from the lower filesystem or |
7c37fbda NB |
25 | upper filesystem that is providing the object. Similarly st_ino will |
26 | only be unique when combined with st_dev, and both of these can change | |
27 | over the lifetime of a non-directory object. Many applications and | |
28 | tools ignore these values and will not be affected. | |
29 | ||
65f26738 AG |
30 | In the special case of all overlay layers on the same underlying |
31 | filesystem, all objects will report an st_dev from the overlay | |
32 | filesystem and st_ino from the underlying filesystem. This will | |
33 | make the overlay mount more compliant with filesystem scanners and | |
34 | overlay objects will be distinguishable from the corresponding | |
35 | objects in the original filesystem. | |
36 | ||
16149013 AG |
37 | On 64bit systems, even if all overlay layers are not on the same |
38 | underlying filesystem, the same compliant behavior could be achieved | |
39 | with the "xino" feature. The "xino" feature composes a unique object | |
40 | identifier from the real object st_ino and an underlying fsid index. | |
41 | If all underlying filesystems support NFS file handles and export file | |
42 | handles with 32bit inode number encoding (e.g. ext4), overlay filesystem | |
43 | will use the high inode number bits for fsid. Even when the underlying | |
44 | filesystem uses 64bit inode numbers, users can still enable the "xino" | |
45 | feature with the "-o xino=on" overlay mount option. That is useful for the | |
46 | case of underlying filesystems like xfs and tmpfs, which use 64bit inode | |
47 | numbers, but are very unlikely to use the high inode number bit. | |
48 | ||
49 | ||
7c37fbda NB |
50 | Upper and Lower |
51 | --------------- | |
52 | ||
53 | An overlay filesystem combines two filesystems - an 'upper' filesystem | |
54 | and a 'lower' filesystem. When a name exists in both filesystems, the | |
55 | object in the 'upper' filesystem is visible while the object in the | |
56 | 'lower' filesystem is either hidden or, in the case of directories, | |
57 | merged with the 'upper' object. | |
58 | ||
59 | It would be more correct to refer to an upper and lower 'directory | |
60 | tree' rather than 'filesystem' as it is quite possible for both | |
61 | directory trees to be in the same filesystem and there is no | |
62 | requirement that the root of a filesystem be given for either upper or | |
63 | lower. | |
64 | ||
65 | The lower filesystem can be any filesystem supported by Linux and does | |
66 | not need to be writable. The lower filesystem can even be another | |
67 | overlayfs. The upper filesystem will normally be writable and if it | |
68 | is it must support the creation of trusted.* extended attributes, and | |
69 | must provide valid d_type in readdir responses, so NFS is not suitable. | |
70 | ||
71 | A read-only overlay of two read-only filesystems may use any | |
72 | filesystem type. | |
73 | ||
74 | Directories | |
75 | ----------- | |
76 | ||
77 | Overlaying mainly involves directories. If a given name appears in both | |
78 | upper and lower filesystems and refers to a non-directory in either, | |
79 | then the lower object is hidden - the name refers only to the upper | |
80 | object. | |
81 | ||
82 | Where both upper and lower objects are directories, a merged directory | |
83 | is formed. | |
84 | ||
85 | At mount time, the two directories given as mount options "lowerdir" and | |
86 | "upperdir" are combined into a merged directory: | |
87 | ||
ef94b186 | 88 | mount -t overlay overlay -olowerdir=/lower,upperdir=/upper,\ |
c3c86996 | 89 | workdir=/work /merged |
7c37fbda NB |
90 | |
91 | The "workdir" needs to be an empty directory on the same filesystem | |
92 | as upperdir. | |
93 | ||
94 | Then whenever a lookup is requested in such a merged directory, the | |
95 | lookup is performed in each actual directory and the combined result | |
96 | is cached in the dentry belonging to the overlay filesystem. If both | |
97 | actual lookups find directories, both are stored and a merged | |
98 | directory is created, otherwise only one is stored: the upper if it | |
99 | exists, else the lower. | |
100 | ||
101 | Only the lists of names from directories are merged. Other content | |
102 | such as metadata and extended attributes are reported for the upper | |
103 | directory only. These attributes of the lower directory are hidden. | |
104 | ||
105 | whiteouts and opaque directories | |
106 | -------------------------------- | |
107 | ||
108 | In order to support rm and rmdir without changing the lower | |
109 | filesystem, an overlay filesystem needs to record in the upper filesystem | |
110 | that files have been removed. This is done using whiteouts and opaque | |
111 | directories (non-directories are always opaque). | |
112 | ||
113 | A whiteout is created as a character device with 0/0 device number. | |
114 | When a whiteout is found in the upper level of a merged directory, any | |
115 | matching name in the lower level is ignored, and the whiteout itself | |
116 | is also hidden. | |
117 | ||
118 | A directory is made opaque by setting the xattr "trusted.overlay.opaque" | |
119 | to "y". Where the upper filesystem contains an opaque directory, any | |
120 | directory in the lower filesystem with the same name is ignored. | |
121 | ||
122 | readdir | |
123 | ------- | |
124 | ||
125 | When a 'readdir' request is made on a merged directory, the upper and | |
126 | lower directories are each read and the name lists merged in the | |
127 | obvious way (upper is read first, then lower - entries that already | |
128 | exist are not re-added). This merged name list is cached in the | |
129 | 'struct file' and so remains as long as the file is kept open. If the | |
130 | directory is opened and read by two processes at the same time, they | |
131 | will each have separate caches. A seekdir to the start of the | |
132 | directory (offset 0) followed by a readdir will cause the cache to be | |
133 | discarded and rebuilt. | |
134 | ||
135 | This means that changes to the merged directory do not appear while a | |
136 | directory is being read. This is unlikely to be noticed by many | |
137 | programs. | |
138 | ||
139 | seek offsets are assigned sequentially when the directories are read. | |
140 | Thus if | |
c3c86996 | 141 | |
7c37fbda NB |
142 | - read part of a directory |
143 | - remember an offset, and close the directory | |
144 | - re-open the directory some time later | |
145 | - seek to the remembered offset | |
146 | ||
147 | there may be little correlation between the old and new locations in | |
148 | the list of filenames, particularly if anything has changed in the | |
149 | directory. | |
150 | ||
151 | Readdir on directories that are not merged is simply handled by the | |
152 | underlying directory (upper or lower). | |
153 | ||
a6c60655 MS |
154 | renaming directories |
155 | -------------------- | |
156 | ||
157 | When renaming a directory that is on the lower layer or merged (i.e. the | |
158 | directory was not created on the upper layer to start with) overlayfs can | |
159 | handle it in two different ways: | |
160 | ||
c3c86996 | 161 | 1. return EXDEV error: this error is returned by rename(2) when trying to |
a6c60655 MS |
162 | move a file or directory across filesystem boundaries. Hence |
163 | applications are usually prepared to hande this error (mv(1) for example | |
164 | recursively copies the directory tree). This is the default behavior. | |
165 | ||
c3c86996 | 166 | 2. If the "redirect_dir" feature is enabled, then the directory will be |
a6c60655 MS |
167 | copied up (but not the contents). Then the "trusted.overlay.redirect" |
168 | extended attribute is set to the path of the original location from the | |
169 | root of the overlay. Finally the directory is moved to the new | |
170 | location. | |
7c37fbda | 171 | |
438c84c2 MS |
172 | There are several ways to tune the "redirect_dir" feature. |
173 | ||
174 | Kernel config options: | |
175 | ||
176 | - OVERLAY_FS_REDIRECT_DIR: | |
177 | If this is enabled, then redirect_dir is turned on by default. | |
178 | - OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW: | |
179 | If this is enabled, then redirects are always followed by default. Enabling | |
180 | this results in a less secure configuration. Enable this option only when | |
181 | worried about backward compatibility with kernels that have the redirect_dir | |
182 | feature and follow redirects even if turned off. | |
183 | ||
184 | Module options (can also be changed through /sys/module/overlay/parameters/*): | |
185 | ||
186 | - "redirect_dir=BOOL": | |
187 | See OVERLAY_FS_REDIRECT_DIR kernel config option above. | |
188 | - "redirect_always_follow=BOOL": | |
189 | See OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW kernel config option above. | |
190 | - "redirect_max=NUM": | |
191 | The maximum number of bytes in an absolute redirect (default is 256). | |
192 | ||
193 | Mount options: | |
194 | ||
195 | - "redirect_dir=on": | |
196 | Redirects are enabled. | |
197 | - "redirect_dir=follow": | |
198 | Redirects are not created, but followed. | |
199 | - "redirect_dir=off": | |
200 | Redirects are not created and only followed if "redirect_always_follow" | |
201 | feature is enabled in the kernel/module config. | |
202 | - "redirect_dir=nofollow": | |
203 | Redirects are not created and not followed (equivalent to "redirect_dir=off" | |
204 | if "redirect_always_follow" feature is not enabled). | |
205 | ||
f168f109 AG |
206 | When the NFS export feature is enabled, every copied up directory is |
207 | indexed by the file handle of the lower inode and a file handle of the | |
208 | upper directory is stored in a "trusted.overlay.upper" extended attribute | |
209 | on the index entry. On lookup of a merged directory, if the upper | |
210 | directory does not match the file handle stores in the index, that is an | |
211 | indication that multiple upper directories may be redirected to the same | |
212 | lower directory. In that case, lookup returns an error and warns about | |
213 | a possible inconsistency. | |
214 | ||
215 | Because lower layer redirects cannot be verified with the index, enabling | |
216 | NFS export support on an overlay filesystem with no upper layer requires | |
217 | turning off redirect follow (e.g. "redirect_dir=nofollow"). | |
218 | ||
f168f109 | 219 | |
7c37fbda NB |
220 | Non-directories |
221 | --------------- | |
222 | ||
223 | Objects that are not directories (files, symlinks, device-special | |
224 | files etc.) are presented either from the upper or lower filesystem as | |
225 | appropriate. When a file in the lower filesystem is accessed in a way | |
226 | the requires write-access, such as opening for write access, changing | |
227 | some metadata etc., the file is first copied from the lower filesystem | |
228 | to the upper filesystem (copy_up). Note that creating a hard-link | |
229 | also requires copy_up, though of course creation of a symlink does | |
230 | not. | |
231 | ||
232 | The copy_up may turn out to be unnecessary, for example if the file is | |
233 | opened for read-write but the data is not modified. | |
234 | ||
235 | The copy_up process first makes sure that the containing directory | |
236 | exists in the upper filesystem - creating it and any parents as | |
237 | necessary. It then creates the object with the same metadata (owner, | |
238 | mode, mtime, symlink-target etc.) and then if the object is a file, the | |
239 | data is copied from the lower to the upper filesystem. Finally any | |
240 | extended attributes are copied up. | |
241 | ||
242 | Once the copy_up is complete, the overlay filesystem simply | |
243 | provides direct access to the newly created file in the upper | |
244 | filesystem - future operations on the file are barely noticed by the | |
245 | overlay filesystem (though an operation on the name of the file such as | |
246 | rename or unlink will of course be noticed and handled). | |
247 | ||
248 | ||
a78d9f0d MS |
249 | Multiple lower layers |
250 | --------------------- | |
251 | ||
252 | Multiple lower layers can now be given using the the colon (":") as a | |
253 | separator character between the directory names. For example: | |
254 | ||
255 | mount -t overlay overlay -olowerdir=/lower1:/lower2:/lower3 /merged | |
256 | ||
6d900f5a MS |
257 | As the example shows, "upperdir=" and "workdir=" may be omitted. In |
258 | that case the overlay will be read-only. | |
259 | ||
260 | The specified lower directories will be stacked beginning from the | |
261 | rightmost one and going left. In the above example lower1 will be the | |
262 | top, lower2 the middle and lower3 the bottom layer. | |
a78d9f0d MS |
263 | |
264 | ||
d5791044 VG |
265 | Metadata only copy up |
266 | -------------------- | |
267 | ||
268 | When metadata only copy up feature is enabled, overlayfs will only copy | |
269 | up metadata (as opposed to whole file), when a metadata specific operation | |
270 | like chown/chmod is performed. Full file will be copied up later when | |
271 | file is opened for WRITE operation. | |
272 | ||
273 | In other words, this is delayed data copy up operation and data is copied | |
274 | up when there is a need to actually modify data. | |
275 | ||
276 | There are multiple ways to enable/disable this feature. A config option | |
277 | CONFIG_OVERLAY_FS_METACOPY can be set/unset to enable/disable this feature | |
278 | by default. Or one can enable/disable it at module load time with module | |
279 | parameter metacopy=on/off. Lastly, there is also a per mount option | |
280 | metacopy=on/off to enable/disable this feature per mount. | |
281 | ||
282 | Do not use metacopy=on with untrusted upper/lower directories. Otherwise | |
283 | it is possible that an attacker can create a handcrafted file with | |
284 | appropriate REDIRECT and METACOPY xattrs, and gain access to file on lower | |
285 | pointed by REDIRECT. This should not be possible on local system as setting | |
286 | "trusted." xattrs will require CAP_SYS_ADMIN. But it should be possible | |
287 | for untrusted layers like from a pen drive. | |
288 | ||
d47748e5 MS |
289 | Note: redirect_dir={off|nofollow|follow(*)} conflicts with metacopy=on, and |
290 | results in an error. | |
291 | ||
292 | (*) redirect_dir=follow only conflicts with metacopy=on if upperdir=... is | |
293 | given. | |
294 | ||
9412812e AG |
295 | Sharing and copying layers |
296 | -------------------------- | |
297 | ||
298 | Lower layers may be shared among several overlay mounts and that is indeed | |
299 | a very common practice. An overlay mount may use the same lower layer | |
300 | path as another overlay mount and it may use a lower layer path that is | |
301 | beneath or above the path of another overlay lower layer path. | |
302 | ||
303 | Using an upper layer path and/or a workdir path that are already used by | |
85fdee1e | 304 | another overlay mount is not allowed and may fail with EBUSY. Using |
0be0bfd2 | 305 | partially overlapping paths is not allowed and may fail with EBUSY. |
85fdee1e AG |
306 | If files are accessed from two overlayfs mounts which share or overlap the |
307 | upper layer and/or workdir path the behavior of the overlay is undefined, | |
308 | though it will not result in a crash or deadlock. | |
9412812e AG |
309 | |
310 | Mounting an overlay using an upper layer path, where the upper layer path | |
311 | was previously used by another mounted overlay in combination with a | |
312 | different lower layer path, is allowed, unless the "inodes index" feature | |
d5791044 | 313 | or "metadata only copy up" feature is enabled. |
9412812e AG |
314 | |
315 | With the "inodes index" feature, on the first time mount, an NFS file | |
316 | handle of the lower layer root directory, along with the UUID of the lower | |
317 | filesystem, are encoded and stored in the "trusted.overlay.origin" extended | |
318 | attribute on the upper layer root directory. On subsequent mount attempts, | |
319 | the lower root directory file handle and lower filesystem UUID are compared | |
320 | to the stored origin in upper root directory. On failure to verify the | |
321 | lower root origin, mount will fail with ESTALE. An overlayfs mount with | |
322 | "inodes index" enabled will fail with EOPNOTSUPP if the lower filesystem | |
323 | does not support NFS export, lower filesystem does not have a valid UUID or | |
324 | if the upper filesystem does not support extended attributes. | |
325 | ||
d5791044 VG |
326 | For "metadata only copy up" feature there is no verification mechanism at |
327 | mount time. So if same upper is mounted with different set of lower, mount | |
328 | probably will succeed but expect the unexpected later on. So don't do it. | |
329 | ||
9412812e AG |
330 | It is quite a common practice to copy overlay layers to a different |
331 | directory tree on the same or different underlying filesystem, and even | |
332 | to a different machine. With the "inodes index" feature, trying to mount | |
333 | the copied layers will fail the verification of the lower root file handle. | |
334 | ||
335 | ||
7c37fbda NB |
336 | Non-standard behavior |
337 | --------------------- | |
338 | ||
5d3211b6 MS |
339 | Current version of overlayfs can act as a mostly POSIX compliant |
340 | filesystem. | |
341 | ||
342 | This is the list of cases that overlayfs doesn't currently handle: | |
343 | ||
344 | a) POSIX mandates updating st_atime for reads. This is currently not | |
345 | done in the case when the file resides on a lower layer. | |
346 | ||
347 | b) If a file residing on a lower layer is opened for read-only and then | |
348 | memory mapped with MAP_SHARED, then subsequent changes to the file are not | |
349 | reflected in the memory mapping. | |
350 | ||
351 | The following options allow overlayfs to act more like a standards | |
352 | compliant filesystem: | |
0c31d675 MS |
353 | |
354 | 1) "redirect_dir" | |
355 | ||
356 | Enabled with the mount option or module option: "redirect_dir=on" or with | |
357 | the kernel config option CONFIG_OVERLAY_FS_REDIRECT_DIR=y. | |
358 | ||
359 | If this feature is disabled, then rename(2) on a lower or merged directory | |
360 | will fail with EXDEV ("Invalid cross-device link"). | |
361 | ||
362 | 2) "inode index" | |
363 | ||
364 | Enabled with the mount option or module option "index=on" or with the | |
365 | kernel config option CONFIG_OVERLAY_FS_INDEX=y. | |
16149013 | 366 | |
0c31d675 MS |
367 | If this feature is disabled and a file with multiple hard links is copied |
368 | up, then this will "break" the link. Changes will not be propagated to | |
369 | other names referring to the same inode. | |
7c37fbda | 370 | |
0c31d675 | 371 | 3) "xino" |
7c37fbda | 372 | |
0c31d675 MS |
373 | Enabled with the mount option "xino=auto" or "xino=on", with the module |
374 | option "xino_auto=on" or with the kernel config option | |
375 | CONFIG_OVERLAY_FS_XINO_AUTO=y. Also implicitly enabled by using the same | |
376 | underlying filesystem for all layers making up the overlay. | |
7c37fbda | 377 | |
0c31d675 MS |
378 | If this feature is disabled or the underlying filesystem doesn't have |
379 | enough free bits in the inode number, then overlayfs will not be able to | |
380 | guarantee that the values of st_ino and st_dev returned by stat(2) and the | |
381 | value of d_ino returned by readdir(3) will act like on a normal filesystem. | |
382 | E.g. the value of st_dev may be different for two objects in the same | |
383 | overlay filesystem and the value of st_ino for directory objects may not be | |
384 | persistent and could change even while the overlay filesystem is mounted. | |
2d8f2908 | 385 | |
16149013 | 386 | |
7c37fbda NB |
387 | Changes to underlying filesystems |
388 | --------------------------------- | |
389 | ||
390 | Offline changes, when the overlay is not mounted, are allowed to either | |
391 | the upper or the lower trees. | |
392 | ||
393 | Changes to the underlying filesystems while part of a mounted overlay | |
394 | filesystem are not allowed. If the underlying filesystem is changed, | |
395 | the behavior of the overlay is undefined, though it will not result in | |
396 | a crash or deadlock. | |
2b7a8f36 | 397 | |
f168f109 AG |
398 | When the overlay NFS export feature is enabled, overlay filesystems |
399 | behavior on offline changes of the underlying lower layer is different | |
400 | than the behavior when NFS export is disabled. | |
401 | ||
402 | On every copy_up, an NFS file handle of the lower inode, along with the | |
403 | UUID of the lower filesystem, are encoded and stored in an extended | |
404 | attribute "trusted.overlay.origin" on the upper inode. | |
405 | ||
406 | When the NFS export feature is enabled, a lookup of a merged directory, | |
407 | that found a lower directory at the lookup path or at the path pointed | |
408 | to by the "trusted.overlay.redirect" extended attribute, will verify | |
409 | that the found lower directory file handle and lower filesystem UUID | |
410 | match the origin file handle that was stored at copy_up time. If a | |
411 | found lower directory does not match the stored origin, that directory | |
412 | will not be merged with the upper directory. | |
413 | ||
414 | ||
a01f64b5 AG |
415 | |
416 | NFS export | |
417 | ---------- | |
418 | ||
419 | When the underlying filesystems supports NFS export and the "nfs_export" | |
420 | feature is enabled, an overlay filesystem may be exported to NFS. | |
421 | ||
422 | With the "nfs_export" feature, on copy_up of any lower object, an index | |
423 | entry is created under the index directory. The index entry name is the | |
424 | hexadecimal representation of the copy up origin file handle. For a | |
425 | non-directory object, the index entry is a hard link to the upper inode. | |
426 | For a directory object, the index entry has an extended attribute | |
427 | "trusted.overlay.upper" with an encoded file handle of the upper | |
428 | directory inode. | |
429 | ||
430 | When encoding a file handle from an overlay filesystem object, the | |
431 | following rules apply: | |
432 | ||
433 | 1. For a non-upper object, encode a lower file handle from lower inode | |
434 | 2. For an indexed object, encode a lower file handle from copy_up origin | |
435 | 3. For a pure-upper object and for an existing non-indexed upper object, | |
436 | encode an upper file handle from upper inode | |
437 | ||
438 | The encoded overlay file handle includes: | |
439 | - Header including path type information (e.g. lower/upper) | |
440 | - UUID of the underlying filesystem | |
441 | - Underlying filesystem encoding of underlying inode | |
442 | ||
443 | This encoding format is identical to the encoding format file handles that | |
444 | are stored in extended attribute "trusted.overlay.origin". | |
445 | ||
446 | When decoding an overlay file handle, the following steps are followed: | |
447 | ||
448 | 1. Find underlying layer by UUID and path type information. | |
449 | 2. Decode the underlying filesystem file handle to underlying dentry. | |
450 | 3. For a lower file handle, lookup the handle in index directory by name. | |
451 | 4. If a whiteout is found in index, return ESTALE. This represents an | |
452 | overlay object that was deleted after its file handle was encoded. | |
453 | 5. For a non-directory, instantiate a disconnected overlay dentry from the | |
454 | decoded underlying dentry, the path type and index inode, if found. | |
455 | 6. For a directory, use the connected underlying decoded dentry, path type | |
456 | and index, to lookup a connected overlay dentry. | |
457 | ||
458 | Decoding a non-directory file handle may return a disconnected dentry. | |
459 | copy_up of that disconnected dentry will create an upper index entry with | |
460 | no upper alias. | |
461 | ||
462 | When overlay filesystem has multiple lower layers, a middle layer | |
463 | directory may have a "redirect" to lower directory. Because middle layer | |
464 | "redirects" are not indexed, a lower file handle that was encoded from the | |
465 | "redirect" origin directory, cannot be used to find the middle or upper | |
466 | layer directory. Similarly, a lower file handle that was encoded from a | |
467 | descendant of the "redirect" origin directory, cannot be used to | |
468 | reconstruct a connected overlay path. To mitigate the cases of | |
469 | directories that cannot be decoded from a lower file handle, these | |
470 | directories are copied up on encode and encoded as an upper file handle. | |
471 | On an overlay filesystem with no upper layer this mitigation cannot be | |
472 | used NFS export in this setup requires turning off redirect follow (e.g. | |
473 | "redirect_dir=nofollow"). | |
474 | ||
475 | The overlay filesystem does not support non-directory connectable file | |
476 | handles, so exporting with the 'subtree_check' exportfs configuration will | |
477 | cause failures to lookup files over NFS. | |
478 | ||
479 | When the NFS export feature is enabled, all directory index entries are | |
480 | verified on mount time to check that upper file handles are not stale. | |
481 | This verification may cause significant overhead in some cases. | |
482 | ||
483 | ||
2b7a8f36 MS |
484 | Testsuite |
485 | --------- | |
486 | ||
05af4fe7 AG |
487 | There's a testsuite originally developed by David Howells and currently |
488 | maintained by Amir Goldstein at: | |
2b7a8f36 | 489 | |
05af4fe7 | 490 | https://github.com/amir73il/unionmount-testsuite.git |
2b7a8f36 MS |
491 | |
492 | Run as root: | |
493 | ||
494 | # cd unionmount-testsuite | |
05af4fe7 | 495 | # ./run --ov --verify |