volumeID/.fseventsd/fseventsd-uuid

Robert Peirce

unread,

Oct 12, 2012, 5:30:18 PM10/12/12

to

Does this change or is it permanently assigned to a partition?

I have a problem where a program I use to edit files in one location
doesn't see the edits when the files are copied to another drive. The
file structure is identical on both drives as is the partition UUID as
recorded on the disc using SDDiskTool from SuperDuper!.

The vendor can't figure it out and I have been at a loss for what might
be different. However, the program may be using the contents of this
file to identify the files it has previously edited. It records a
"UUID" in the sidecar but I have no idea where that comes from or how it
is related to the physical disks. I have inquired but don't have an
answer yet.

If the contents of this file never change, a possible solution would be
to make the files identical on both disks, but I don't really know what
problems that might cause, if any. Does anybody know?

David Empson

unread,

Oct 12, 2012, 10:22:26 PM10/12/12

to

Robert Peirce <b...@peirce-family.com> wrote:

> Does this change or is it permanently assigned to a partition?

The FSEvents database is associated with a particular volume (partition)
and is used to allow software like Spotlight and Time Machine work out
quickly where file changes have occurred, so they can be indexed or
backed up.

> I have a problem where a program I use to edit files in one location
> doesn't see the edits when the files are copied to another drive.

FSEvents has nothing to do with the content of files, or the history of
changes to files. It only tracks where file system changes have occured,
and is not normally used by applications.

If an application wants to know whether a particular document has
changed, it would normally do that by looking at the file modification
date.

> The file structure is identical on both drives as is the partition UUID as
> recorded on the disc using SDDiskTool from SuperDuper!.

Are you saying you have two partitions with the same UUID? That is not
normal and could cause problems. UUIDs are supposed to be unique.
("Universally Unique Identifier" is what it stands for.)

> The vendor can't figure it out and I have been at a loss for what might
> be different. However, the program may be using the contents of this
> file to identify the files it has previously edited. It records a
> "UUID" in the sidecar but I have no idea where that comes from or how it
> is related to the physical disks. I have inquired but don't have an
> answer yet.

The UUID for a volume is generated automatically at the time the volume
is erased. It can be used internally to distinguish between two volumes
that otherwise appear to be the same, e.g. it is probably used inside
aliases to identify which volume a file is located on, as a more unique
reference than the volume name, which can be the same without confusing
aliases.

> If the contents of this file never change, a possible solution would be
> to make the files identical on both disks, but I don't really know what
> problems that might cause, if any. Does anybody know?

Need more information to understand the problem. What is the nature of
the application and its document files, and where are the edits stored
if not within the document file itself?

If you are referring to the Versions mechanism that Apple introduced in
Lion (used by TextEdit, Preview, the iWork suite, and a growing number
of third party applications), the version history is tied to the
original volume and doesn't go with the document if you copy or move the
document to another volume.

Historical data maintained by Versions is stored in an SQLite database
and associated files in the /.DocumentRevisions-V100 folder, but I
wouldn't recommend poking around inside there as it is being updated
regularly by the system (e.g. to prune old versions every hour).

--
David Empson
dem...@actrix.gen.nz

Robert Peirce

unread,

Oct 15, 2012, 7:13:11 PM10/15/12

to

In article <1krwj5d.1b1uv3410g5khsN%dem...@actrix.gen.nz>,

dem...@actrix.gen.nz (David Empson) wrote:

> Are you saying you have two partitions with the same UUID? That is not
> normal and could cause problems. UUIDs are supposed to be unique.
> ("Universally Unique Identifier" is what it stands for.)

These are partitions on two separate drives, one in VA and one in PA. I
was having a problem with an app that looked at this number and would
work on one but not the other. Having the same UUIDs for each partition
on the separate drives solved that problem. It has been working for
several years.

nospam

unread,

Oct 15, 2012, 7:59:15 PM10/15/12

to

In article <bob-DB5694.1...@5ad64b5e.bb.sky.com>, Robert

Peirce <b...@peirce-family.com> wrote:

> > Are you saying you have two partitions with the same UUID? That is not
> > normal and could cause problems. UUIDs are supposed to be unique.
> > ("Universally Unique Identifier" is what it stands for.)
>
> These are partitions on two separate drives, one in VA and one in PA. I
> was having a problem with an app that looked at this number and would
> work on one but not the other. Having the same UUIDs for each partition
> on the separate drives solved that problem. It has been working for
> several years.

having multiple drives or partitions with the same uuid is just asking
for problems.