Mounting a union file system

These options are supported when you are mounting a union file system.

upperdir

Specifies the top-level read/write directory. Only one directory can be specified. All changes to the file system are reflected in this directory. During path name resolution, this directory is the first directory in the search order.

This option is required unless the union file system is being mounted read-only. Because directories can contain a colon in the name, the backslash (\) escape character must be used if a colon appears in one of the specified directories.

Restriction: The upperdir option cannot be used on multiple mounts of the union file system.

lowerdir

Specifies one or more read-only directories that are separated by colons (:). During path name resolution, these directories are searched after the directory that is specified in the upperdir option. The search order is determined by the order in which they were specified (left to right).

This option is required. Because directories can contain a colon in the name, the backslash (\) escape character must be used if a colon appears in one of the specified directories.

The lowerdir option can be used on multiple mounts of the union file system.

mergeufs=[on|off]

The upperdir and lowerdir options cannot specify a path that resides within another UFS file system. Specifying mergeufs=on will parse the merged directories from union file systems that are supplied in the lower directory option. Those directories are added to the union file system that are being mounted.

This option is optional and the default value is on.

metacopy=[on|off]

Specifies whether a change in file or directory attributes will cause an attribute-only copyup operation. When this option is off, all copyup operations are full copyup operations.

This option is optional and the default value is off.

redirect_dir=[on|off]

Specifies whether a rename operation of a directory in a lower directory can create a redirected directory. When this option is on, any rename of a directory with parts in a lower directory will create a directory with the new name in the upper directory. However, the content of that directory is not copied up along with the directory. Any reference to that path is redirected to the merged directory. When redirect_dir=off is specified, all renames of directories existing in the lower directory will fail with EXDEV and JrUFSNoRedirect.

This option is optional and the default value is on.

supercopy=[on|off]

Specifies whether a copyup of a file or directory should change the owner of the file or directory to the current user performing the copyup.

This option is optional and the default value is off.

workdir

Specifies a required work directory that is used internally by the union file system. This directory must be empty at mount time. It must also be on the same file system as the directory specified in the upperdir option.

This option is required.

Each mount option must be separated by commas. Each mount option must be followed by = and the path name of the specified directory. For example:

upperdir=/tmp/mydir1,lowerdir=mydir2:mydir3,workdir=/wrk