[Discuss] Rsync "one file system"

[dsr at randomstring.org (Dan Ritter)]

jbk wrote: 
> On 10/24/20 12:51 PM, Dan Ritter wrote:
> > jbk wrote:
> > > I was cloning a fedora31 system to another partition using rsync using the
> > > -x option to restrict decent to one file system, at least that was what I
> > > thought, but the contents below the mount point were copied anyway.
> > > 
> > > rsync -ax bin boot data (<- mounted to separate partition) ... <destination>
> > > 
> > > So what am I not understanding?
> > Did it look like this?
> > /dev/sdd1 on / type blah blah
> > /dev/sdd2 on /data type blah blah
> > 
> > or like this?
> > 
> > /dev/sdd1 on / type blah blah
> > /dev/sdd3 on /data/thingy type blah blah
> > 
> > rsync -x includes anything you explicitly mention (so, all
> > subdirectories of the top situation) and excludes filesystems
> > mounted underneath what you mention (so, not /data/thingy in the
> > bottom situation).
> > 
> > -dsr-
> 
> So data is a mount point in character with the first example, it is not a
> bind mount. I understand that by using the "-a" option that recursion is
> implied but if I added "-x" that it would skip recursion into normal mount
> points.

It skips recursion into mount points that are different from
something that you told it about.

If you say 
 rsync -a -x / /home /var

it will get everything that is directly on your root, everything
in /home, even if /home is a mount point, and everything in /var,
even if /var is a mount point, but it will skip:

/tmp  -- a mount point under /
/var/tmp  -- a mount point under /var

Does that help?

> > /rsync -x includes anything you explicitly mention (so, all
> > subdirectories of the top situation) and excludes filesystems mounted
> > underneath what you mention (so, not /data/thingy in the bottom
> > situation)./
> So if I'm understanding this, if there were a mount point /backups below
> /data such as /data/backups then /backups would not be recursed because it
> was not part of the top level listing in the command.

Correct. 

-dsr-