Rsync backup issues using relative paths and LVM snapshots

[Alex Ferrara]

Hi everyone,

I have been using rsync for years to perform off-site backups, and have recently come up with a problem that is starting to hurt my head. I am at the point where I am starting to think that there is a method to achieve my desired outcome that I cannot see.

First, a bit of history. I usually just set up a script that runs many rsync commands in sequence to perform the desired actions. As it is usually an off-site sync, I pick and choose what directories should be sent over the wire. I have one site that has about 6 servers, all with custom scripts, and I now need to perform the off-site sync to more than one location. I could have just put more into these scripts, but as they were getting quite long, I decided to streamline the scripts a little.

The new scripts take options from a configuration file, and the sync script will be the same on all servers, which will make on-going management easier. These configuration options include a list of directories to be rsync'd. As some of these directories are a few levels deep, I have been using the -R (relative) option to automatically generate the full paths on the destination system. Up until this point, everything is working as expected.

The problem arises when I have a directory that will more than likely change between each sync. One example of this is my mail spool directory. Since emails come in all the time, the sync will be marked as failed most of the time. The way I was dealing with this in my sequential scripts was to take a LVM snapshot, and then rsync the snapshot to the destination server.

My problem is that if I mark a directory to have a snapshot created before rsync and use the -R (relative) option, the directory structure on the destination system will be the relative path of where I mounted the snapshot (/mnt/sync-snapshot in my case). If I don't use the -R option, and I am trying to back up a snapshot of the directory /var/spool/cyrus, how can I get rsync to create the /var/spool directories for me before the sync?

The following works, but creates /mnt/sync-snapshot on the destination server
root at percy:/# rsync -auRv /mnt/sync-snapshot ds9::kingston

The following doesn't work because /var/spool does not exist on the destination server, and therefore the mkdir fails.
root at percy:/# rsync -auv /mnt/sync-snapshot ds9::kingston/var/spool/cyrus/
sending incremental file list
rsync: mkdir "/var/spool/cyrus" (in kingston) failed: No such file or directory (2)
rsync: read error: Connection reset by peer (104)
rsync error: error in rsync protocol data stream (code 12) at io.c(760) [sender=3.0.7]

Creating the directories manually on the destination server is not desirable. I really want to put the logic in the script so it is easy to bring another backup location online easily.

Thanks for your time.

Alex Ferrara
Director
Receptive IT Soutions