unionfs(8)

NAME

Unionfs - a unification file system for Linux

SYNOPSIS

unionctl UNION ACTION [ OPTIONS ]
unionctl UNION --add [ --before BRANCH | --after BRANCH  ]
[ --mode (rw|ro|nfsro) ] DIRECTORY
unionctl UNION --remove BRANCH
unionctl UNION --mode BRANCH (rw|ro|nfsro)
unionctl UNION --list

DESCRIPTION

unionctl is used to control a unionfs file system. The

first argument is a union, which is the mount point of unionfs,

or any file within unionfs. The second argument is an action.

Currently unionctl supports file actions: --add, --remove,

--mode, --list and --query. Further arguments are action depen

dent.

When a branch is required as an argument, it can be speci

fied in two ways. The easiest way is to specify the path to the

branch. If the path is used multiple times in the union, the

highest priority branch will be used. A branch can also be spec

ified as an index starting from zero.

ACTIONS

--add add a branch into a union. By default a read-write

branch will be added as the first component of the union.

The order of branches can be modified with --before

and --after. Each of these takes a single branch as an argument.

If --before is specified the new branch will be added before the

specified branch; and if --after is specified the new branch will

be added after the specified branch.

Finally, --mode will set the permissions on the new

branch. --mode requires one argument, which is "rw" for a read

write branch, "ro" for a read-only branch and "nfsro" for read

only access on NFS shares (see unionfs(4) for further informa

tion).

Note: The directory to add must be the last argu

ment.

--remove

removes a branch from a union. Branches with open

files can not be removed.

--query option.

To remove a branch, unionctl performs an ioctl that

operates on a file descriptor. If the root directory is opened,

then the branch will necessarily be busy.

--mode sets the permissions of a branch. --mode requires

two arguments, the first is the branch to operate on; and the

second is what mode to set. The allowed modes are "rw" for read

write access, "ro" for read-only access and "nfsro" for read-only

access on NFS shares (see unionfs(4) for further information).

--list list branches within the union (and also their per

missions).

--query

lists the branches where a given file exists.

--query requires one argument : the name of the file to be exam

ined. The output is a list of branches where the file exists and

the permissions of the branches.

AUTHORS

Charles Wright <cwright@cs.sunysb.edu>, Mohammad Zubair

<mzubair@ic.sunysb.edu>, Erez Zadok <ezk@cs.sunysb.edu>

SEE ALSO

unionfs(4), uniondbg(8), http://unionfs.filesystems.org/

Linux January 2006

UNIONFS(8)