I was setting up a machine to handle some of our backups at work. It's not a critical system, so instead of setting up a RAID across 3 250GB drives, I just set up LVM so I could take advantage of all 750GB. This were going along fine, but then I wanted to see what the status of LVM was...So I ran 'lvdisplay' and got this very disturbing message: Couldn't find device with uuid 'tcRo2m-XJ1W-JFUh-FuYP-dbbW-RHSx-FFnQ4r'. Couldn't find all physical volumes for volume group ide_drives. Couldn't find device with uuid 'tcRo2m-XJ1W-JFUh-FuYP-dbbW-RHSx-FFnQ4r'. Couldn't find all physical volumes for volume group ide_drives. Volume group "ide_drives" not found Uh oh...Did one of the drives fail already? 'pvscan', etc. didn't yield any better results. But then I notice the device that isn't found is '/dev/hdb', which does have the correct uuid. But it also happens that '/dev/cdrom' is a symlink to '/dev/hdb', so lvm was ignoring that device because it thought it was a cdrom device! AAARGH. Only took me 2 hours to figure that one out. I'm hoping this post can save somebody else some time. On that same machine, I wanted to set up rsync to handle the backups since it's well suited for that purpose. I had just discovered rsync's filter rule syntax so I wanted to play around with that to specify which directories on which machines should be backed up. Lets say my directory structure looks like this: / /etc /home -> /mnt/raid/home /mnt /mnt/raid/ /mnt/raid/home /proc /tmp ... and I want to back up both /etc and /home. So I tried this set of rsync filter rules: + /etc/ + /etc/** + /home/ + /home/** - * No luck at all. rsync refused to copy over the home directories. Again, several hours were lost figuring this out. I think what was happening was that rsync was happily copying the /home symlink and not looking deeper into the directory structure. So when it came to the '- *' rule, the actual home directories were being excluded. I solved this by adding + /mnt/ + /mnt/raid/ + /mnt/raid/home/ + /mnt/raid/home/** to my filter rules instead of the '/home' stuff.