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Diffstat (limited to 'sys-utils/mount.8')
| -rw-r--r-- | sys-utils/mount.8 | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/sys-utils/mount.8 b/sys-utils/mount.8 index 004a51324..46c934adc 100644 --- a/sys-utils/mount.8 +++ b/sys-utils/mount.8 @@ -2389,6 +2389,41 @@ Set the file permission on the filesystem. The umask value is given in octal. By default, the files are owned by root and not readable by somebody else. +.SH "Mount options for overlay" +Since Linux 3.18 the overlay pseudo filesystem implements a union mount for +other file systems. + +An overlay filesystem combines two filesystems - an \fBupper\fR filesystem and +a \fBlower\fR filesystem. When a name exists in both filesystems, the object +in the upper filesystem is visible while the object in the lower filesystem is +either hidden or, in the case of directories, merged with the upper object. + +The lower filesystem can be any filesystem supported by Linux and does not need +to be writable. The lower filesystem can even be another overlayfs. The upper +filesystem will normally be writable and if it is it must support the creation +of trusted.* extended attributes, and must provide valid d_type in readdir +responses, so NFS is not suitable. + +A read-only overlay of two read-only filesystems may use any filesystem type. +The options \fBlowerdir\fR and \fBupperdir\fR are combined into a merged +directory by using: + +.RS +.br +.BR "mount \-t overlay overlay \-olowerdir=/lower,upperdir=/upper,workdir=/work /merged" +.br +.RE + +.TP +.BI lowerdir= directory +Any filesystem, does not need to be on a writable filesystem. +.TP +.BI upperdir= directory +The upperdir is normally on a writable filesystem. +.TP +.BI workdir= directory +The workdir needs to be an empty directory on the same filesystem as upperdir. + .SH "Mount options for proc" .TP \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP |