unionctl UNION ACTION [
OPTIONS
]
unionctl UNION --add [
--before BRANCH |
--after BRANCH ] [
--mode (rw|ro) ]
DIRECTORY unionctl UNION --remove BRANCH unionctl UNION --mode BRANCH (rw|ro)
unionctl UNION --list
DESCRIPTION
unionctl is used to control a unionfs file system. The first argument is a union, which
is the mountpoint of unionfs, or any file within unionfs. The second argument is
an action. Currently
unionctl supports four actions: --add, --remove, --mode, and --list. Further arguments
are action dependent.
When a branch is required as an argument, it can be specified 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 specified 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 either "rw" for a read-write branch or "ro" for a
read-only branch.
Note: The directory to add must be the last argument.
"--remove"
removes a branch from a union. Branches with open files can not be removed.
You can not use the root directory of the union to specify which union should
be operated on. You must chose a file or directory that does not exist within
the branch, otherwise you will get a "Device or resource busy." error.
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 "ro" for read-only access and "rw" for read-write access.
"--list"
list branches within the union (and also their permissions).
AUTHORS
Charles Wright <cwright@cs.sunysb.edu>,
Mohammad Zubair <mzubair@ic.sunysb.edu>,
Erez Zadok <ezk@cs.sunysb.edu>
