> But I am chaging my mind again, and thinking about another new option
> "nocheck".
>
> - without "nocheck" (default), aufs checks the consistency even if the
> src/dst are specified.
> - specifying "nocheck" explicitly, aufs skips the check. this option is
> just for the users who know what he is doing.
>
> Hmm, probably I need to review the design again.
Here is a (fomatted) user's manual of the command aumvdown.
The semantics is that "specifying source/target branch means 'nocheck'
automatically". So the "nocheck" option will not be implemented.
Any comments are welcome.
J. R. Okajima
----------------------------------------------------------------------
NAME
aumvdown - moves-down a file between aufs branches
SYNOPSIS
aumvdown [options] file ...
DESCRIPTION
"aumvdown" command finds the first branch where the given file exists,
copies it to the next lower writable branch, and then removes the file
on the first branch.
You can customize the behaviour by specifing options. See OPTIONS in
detail.
There are several conditions to achieve the operation.
o It is obvious that when the file exists between the first
and the next lower writable branches, or hidden by the
whiteout or direcotry's opaque-ness, then the operation
failed (by default). Because it breaks the consistency in
aufs world.
o Files in use (both in aufs world and in branch filesystem)
are not be handled.
o Hard-linked (both in aufs world and in branch filesystem, or
pseudo-linked in aufs world) files are not be handled.
For such file, remount aufs or use "auplink."
o Directories are not be handled since the action doesn't
behave recursivly and the moving-down an empty dir has less
meaning.
When all these conditions are not satisfied, EBUSY will be returned.
Note that any directory in aufs can be "opaque". If any of the interme-
diate dir of the file between the source and taget branch is set to
opaque, then the command returns an error (by default) since you won't
see the moved-down (or copied-down) file. In order to reduce setting
the opaque-ness for directories, it is strongly discouraged to specify
"diropq=always." This confusing situation can happen when a user
rename(2) a dir directly on a branch (by-passing aufs) since aufs can-
not stop such user's direct rename(2) operation.
Also note about the whiteout on the lower branches, including the read-
only branches with the attribute "=ro+wh" is set. Similar to the
opaqued dir, the whiteout can hide the lower same-named file and you
may not see the moved (or copied) file either. Of course the command
will return an error when such whiteout is found (by default). Again
direct change on the branch (by-passing aufs) can cause such confusing
situation.
OPTIONS
-s index | --source-index index | --source-branch path
-t index | --target-index index | --target-branch path
By default, the source branch is the first branch where the file
exists, and the target branch is the next lower writable branch.
Both branches must be natively writable and marked as writable
in aufs world, and the same-named file should not exist on the
intermediate branches. Otherwise the command will return an
error.
By specifying source and target branch explicitly, you can
choose other source/target branch even if the branch permission
is marked as readonly in aufs world. And --overwrite option is
automatically set. You can specify the branch, either by the
branch path or by the branch index.
Obviously no can write to the natively readonly filesystem. In
this case, EROFS will be returned.
Caution: It means these options skip the internal checkings
around the branch and force aumvdown(8) to use the specified
branch. The result may confuse you since it can easily hide the
moved-down (or copied-down) file.
-w | --overwrite
When this option is enabled and if the same named file exists on
the target branch, it will be over-written. Otherwise EEXIST
will be returned unless the branch is explicitly specified (by
-t or something).
-c | --copy
Essentially this option choose the action whether "copy" or
"move." Unless this option is specified, the source file on the
upper writable branch is removed after copying-down, which
results the "move" operation.
-i | --interactive
Prompt to the user for every given file.
-v | --verbose
Make it verbose particulary for the error cases. Note that the
messages are printed by kernel (and left in your syslog).
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