1config OVERLAY_FS 2 tristate "Overlay filesystem support" 3 select EXPORTFS 4 help 5 An overlay filesystem combines two filesystems - an 'upper' filesystem 6 and a 'lower' filesystem. When a name exists in both filesystems, the 7 object in the 'upper' filesystem is visible while the object in the 8 'lower' filesystem is either hidden or, in the case of directories, 9 merged with the 'upper' object. 10 11 For more information see Documentation/filesystems/overlayfs.txt 12 13config OVERLAY_FS_REDIRECT_DIR 14 bool "Overlayfs: turn on redirect dir feature by default" 15 depends on OVERLAY_FS 16 help 17 If this config option is enabled then overlay filesystems will use 18 redirects when renaming directories by default. In this case it is 19 still possible to turn off redirects globally with the 20 "redirect_dir=off" module option or on a filesystem instance basis 21 with the "redirect_dir=off" mount option. 22 23 Note, that redirects are not backward compatible. That is, mounting 24 an overlay which has redirects on a kernel that doesn't support this 25 feature will have unexpected results. 26 27config OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW 28 bool "Overlayfs: follow redirects even if redirects are turned off" 29 default y 30 depends on OVERLAY_FS 31 help 32 Disable this to get a possibly more secure configuration, but that 33 might not be backward compatible with previous kernels. 34 35 For more information, see Documentation/filesystems/overlayfs.txt 36 37config OVERLAY_FS_INDEX 38 bool "Overlayfs: turn on inodes index feature by default" 39 depends on OVERLAY_FS 40 help 41 If this config option is enabled then overlay filesystems will use 42 the inodes index dir to map lower inodes to upper inodes by default. 43 In this case it is still possible to turn off index globally with the 44 "index=off" module option or on a filesystem instance basis with the 45 "index=off" mount option. 46 47 The inodes index feature prevents breaking of lower hardlinks on copy 48 up. 49 50 Note, that the inodes index feature is read-only backward compatible. 51 That is, mounting an overlay which has an index dir on a kernel that 52 doesn't support this feature read-only, will not have any negative 53 outcomes. However, mounting the same overlay with an old kernel 54 read-write and then mounting it again with a new kernel, will have 55 unexpected results. 56